Support memory aliasing (#2954)

* Back to the origins: Make memory manager take guest PA rather than host address once again

* Direct mapping with alias support on Windows

* Fixes and remove more of the emulated shared memory

* Linux support

* Make shared and transfer memory not depend on SharedMemoryStorage

* More efficient view mapping on Windows (no more restricted to 4KB pages at a time)

* Handle potential access violations caused by partial unmap

* Implement host mapping using shared memory on Linux

* Add new GetPhysicalAddressChecked method, used to ensure the virtual address is mapped before address translation

Also align GetRef behaviour with software memory manager

* We don't need a mirrorable memory block for software memory manager mode

* Disable memory aliasing tests while we don't have shared memory support on Mac

* Shared memory & SIGBUS handler for macOS

* Fix typo + nits + re-enable memory tests

* Set MAP_JIT_DARWIN on x86 Mac too

* Add back the address space mirror

* Only set MAP_JIT_DARWIN if we are mapping as executable

* Disable aliasing tests again (still fails on Mac)

* Fix UnmapView4KB (by not casting size to int)

* Use ref counting on memory blocks to delay closing the shared memory handle until all blocks using it are disposed

* Address PR feedback

* Make RO hold a reference to the guest process memory manager to avoid early disposal

Co-authored-by: nastys <nastys@users.noreply.github.com>

ARMeilleure/Signal/NativeSignalHandler.cs

@@ -103,7 +103,7 @@ namespace ARMeilleure.Signal
                     // Unix siginfo struct locations.
                     // NOTE: These are incredibly likely to be different between kernel version and architectures.
 
-                    config.StructAddressOffset = 16; // si_addr
+                    config.StructAddressOffset = OperatingSystem.IsMacOS() ? 24 : 16; // si_addr
                     config.StructWriteOffset = 8; // si_code
 
                     _signalHandlerPtr = Marshal.GetFunctionPointerForDelegate(GenerateUnixSignalHandler(_handlerConfig));

ARMeilleure/Signal/UnixSignalHandlerRegistration.cs

@@ -21,6 +21,7 @@ namespace ARMeilleure.Signal
     static class UnixSignalHandlerRegistration
     {
         private const int SIGSEGV = 11;
+        private const int SIGBUS = 10;
         private const int SA_SIGINFO = 0x00000004;
 
         [DllImport("libc", SetLastError = true)]
@@ -43,7 +44,17 @@ namespace ARMeilleure.Signal
 
             if (result != 0)
             {
-                throw new InvalidOperationException($"Could not register sigaction. Error: {result}");
+                throw new InvalidOperationException($"Could not register SIGSEGV sigaction. Error: {result}");
+            }
+
+            if (OperatingSystem.IsMacOS())
+            {
+                result = sigaction(SIGBUS, ref sig, out SigAction oldb);
+
+                if (result != 0)
+                {
+                    throw new InvalidOperationException($"Could not register SIGBUS sigaction. Error: {result}");
+                }
             }
 
             return old;
@@ -51,7 +62,7 @@ namespace ARMeilleure.Signal
 
         public static bool RestoreExceptionHandler(SigAction oldAction)
         {
-            return sigaction(SIGSEGV, ref oldAction, out SigAction _) == 0;
+            return sigaction(SIGSEGV, ref oldAction, out SigAction _) == 0 && (!OperatingSystem.IsMacOS() || sigaction(SIGBUS, ref oldAction, out SigAction _) == 0);
         }
     }
 }

ARMeilleure/Translation/IntervalTree.cs

@@ -8,7 +8,7 @@ namespace ARMeilleure.Translation
     /// </summary>
     /// <typeparam name="K">Key</typeparam>
     /// <typeparam name="V">Value</typeparam>
-    public class IntervalTree<K, V> where K : IComparable<K>
+    class IntervalTree<K, V> where K : IComparable<K>
     {
         private const int ArrayGrowthSize = 32;
 
@@ -53,7 +53,7 @@ namespace ARMeilleure.Translation
         /// <returns>Number of intervals found</returns>
         public int Get(K start, K end, ref K[] overlaps, int overlapCount = 0)
         {
-            GetValues(_root, start, end, ref overlaps, ref overlapCount);
+            GetKeys(_root, start, end, ref overlaps, ref overlapCount);
 
             return overlapCount;
         }
@@ -180,20 +180,20 @@ namespace ARMeilleure.Translation
         }
 
         /// <summary>
-        /// Retrieve all values that overlap the given start and end keys.
+        /// Retrieve all keys that overlap the given start and end keys.
         /// </summary>
         /// <param name="start">Start of the range</param>
         /// <param name="end">End of the range</param>
         /// <param name="overlaps">Overlaps array to place results in</param>
         /// <param name="overlapCount">Overlaps count to update</param>
-        private void GetValues(IntervalTreeNode<K, V> node, K start, K end, ref K[] overlaps, ref int overlapCount)
+        private void GetKeys(IntervalTreeNode<K, V> node, K start, K end, ref K[] overlaps, ref int overlapCount)
         {
             if (node == null || start.CompareTo(node.Max) >= 0)
             {
                 return;
             }
 
-            GetValues(node.Left, start, end, ref overlaps, ref overlapCount);
+            GetKeys(node.Left, start, end, ref overlaps, ref overlapCount);
 
             bool endsOnRight = end.CompareTo(node.Start) > 0;
             if (endsOnRight)
@@ -208,7 +208,7 @@ namespace ARMeilleure.Translation
                     overlaps[overlapCount++] = node.Start;
                 }
 
-                GetValues(node.Right, start, end, ref overlaps, ref overlapCount);
+                GetKeys(node.Right, start, end, ref overlaps, ref overlapCount);
             }
         }
 
@@ -717,40 +717,40 @@ namespace ARMeilleure.Translation
     /// </summary>
     /// <typeparam name="K">Key type of the node</typeparam>
     /// <typeparam name="V">Value type of the node</typeparam>
-    internal class IntervalTreeNode<K, V>
+    class IntervalTreeNode<K, V>
     {
-        internal bool Color = true;
-        internal IntervalTreeNode<K, V> Left = null;
-        internal IntervalTreeNode<K, V> Right = null;
-        internal IntervalTreeNode<K, V> Parent = null;
+        public bool Color = true;
+        public IntervalTreeNode<K, V> Left = null;
+        public IntervalTreeNode<K, V> Right = null;
+        public IntervalTreeNode<K, V> Parent = null;
 
         /// <summary>
         /// The start of the range.
         /// </summary>
-        internal K Start;
+        public K Start;
 
         /// <summary>
         /// The end of the range.
         /// </summary>
-        internal K End;
+        public K End;
 
         /// <summary>
         /// The maximum end value of this node and all its children.
         /// </summary>
-        internal K Max;
+        public K Max;
 
         /// <summary>
         /// Value stored on this node.
         /// </summary>
-        internal V Value;
+        public V Value;
 
         public IntervalTreeNode(K start, K end, V value, IntervalTreeNode<K, V> parent)
         {
-            this.Start = start;
-            this.End = end;
-            this.Max = end;
-            this.Value = value;
-            this.Parent = parent;
+            Start = start;
+            End = end;
+            Max = end;
+            Value = value;
+            Parent = parent;
         }
     }
 }

Ryujinx.Common/Collections/IntervalTree.cs

@@ -1,7 +1,5 @@
 using System;
-using System.Collections;
 using System.Collections.Generic;
-using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 
 namespace Ryujinx.Common.Collections
@@ -212,7 +210,7 @@ namespace Ryujinx.Common.Collections
         /// <param name="overlaps">Overlaps array to place results in</param>
         /// <param name="overlapCount">Overlaps count to update</param>
         private void GetValues(IntervalTreeNode<K, V> node, K start, K end, ref V[] overlaps, ref int overlapCount)
-        {   
+        {
             if (node == null || start.CompareTo(node.Max) >= 0)
             {
                 return;
@@ -624,7 +622,7 @@ namespace Ryujinx.Common.Collections
                 node.Right = LeftOf(right);
                 if (node.Right != null)
                 {
-                    node.Right.Parent = node; 
+                    node.Right.Parent = node;
                 }
                 IntervalTreeNode<K, V> nodeParent = ParentOf(node);
                 right.Parent = nodeParent;
@@ -638,7 +636,7 @@ namespace Ryujinx.Common.Collections
                 }
                 else
                 {
-                    nodeParent.Right = right; 
+                    nodeParent.Right = right;
                 }
                 right.Left = node;
                 node.Parent = right;
@@ -779,37 +777,37 @@ namespace Ryujinx.Common.Collections
     /// </summary>
     /// <typeparam name="K">Key type of the node</typeparam>
     /// <typeparam name="V">Value type of the node</typeparam>
-    internal class IntervalTreeNode<K, V>
+    class IntervalTreeNode<K, V>
     {
-        internal bool Color = true;
-        internal IntervalTreeNode<K, V> Left = null;
-        internal IntervalTreeNode<K, V> Right = null;
-        internal IntervalTreeNode<K, V> Parent = null;
+        public bool Color = true;
+        public IntervalTreeNode<K, V> Left = null;
+        public IntervalTreeNode<K, V> Right = null;
+        public IntervalTreeNode<K, V> Parent = null;
 
         /// <summary>
         /// The start of the range.
         /// </summary>
-        internal K Start;
+        public K Start;
 
         /// <summary>
         /// The end of the range - maximum of all in the Values list.
         /// </summary>
-        internal K End;
+        public K End;
 
         /// <summary>
         /// The maximum end value of this node and all its children.
         /// </summary>
-        internal K Max;
+        public K Max;
 
-        internal List<RangeNode<K, V>> Values;
+        public List<RangeNode<K, V>> Values;
 
         public IntervalTreeNode(K start, K end, V value, IntervalTreeNode<K, V> parent)
         {
-            this.Start = start;
-            this.End = end;
-            this.Max = end;
-            this.Values = new List<RangeNode<K, V>> { new RangeNode<K, V>(start, end, value) };
-            this.Parent = parent;
+            Start = start;
+            End = end;
+            Max = end;
+            Values = new List<RangeNode<K, V>> { new RangeNode<K, V>(start, end, value) };
+            Parent = parent;
         }
     }
 }

Ryujinx.Common/Collections/TreeDictionary.cs

@@ -921,10 +921,10 @@ namespace Ryujinx.Common.Collections
 
         public bool IsReadOnly => false;
 
-        public V this[K key] 
-        { 
+        public V this[K key]
+        {
             get => Get(key);
-            set => Add(key, value); 
+            set => Add(key, value);
         }
 
         #endregion
@@ -967,20 +967,20 @@ namespace Ryujinx.Common.Collections
     /// </summary>
     /// <typeparam name="K">Key of the node</typeparam>
     /// <typeparam name="V">Value of the node</typeparam>
-    internal class Node<K, V>
+    class Node<K, V>
     {
-        internal bool Color = true;
-        internal Node<K, V> Left = null;
-        internal Node<K, V> Right = null;
-        internal Node<K, V> Parent = null;
-        internal K Key;
-        internal V Value;
+        public bool Color = true;
+        public Node<K, V> Left = null;
+        public Node<K, V> Right = null;
+        public Node<K, V> Parent = null;
+        public K Key;
+        public V Value;
 
         public Node(K key, V value, Node<K, V> parent)
         {
-            this.Key = key;
-            this.Value = value;
-            this.Parent = parent;
+            Key = key;
+            Value = value;
+            Parent = parent;
         }
     }
 }

Ryujinx.Cpu/MemoryEhMeilleure.cs

@@ -24,7 +24,7 @@ namespace Ryujinx.Cpu
             _baseAddress = (ulong)_addressSpace.Pointer;
             ulong endAddress = _baseAddress + addressSpace.Size;
 
-            _trackingEvent = new TrackingEventDelegate(tracking.VirtualMemoryEvent);
+            _trackingEvent = new TrackingEventDelegate(tracking.VirtualMemoryEventEh);
             bool added = NativeSignalHandler.AddTrackedRegion((nuint)_baseAddress, (nuint)endAddress, Marshal.GetFunctionPointerForDelegate(_trackingEvent));
 
             if (!added)

Ryujinx.Cpu/MemoryManager.cs

@@ -25,6 +25,7 @@ namespace Ryujinx.Cpu
 
         private const int PointerTagBit = 62;
 
+        private readonly MemoryBlock _backingMemory;
         private readonly InvalidAccessHandler _invalidAccessHandler;
 
         /// <summary>
@@ -50,10 +51,12 @@ namespace Ryujinx.Cpu
         /// <summary>
         /// Creates a new instance of the memory manager.
         /// </summary>
+        /// <param name="backingMemory">Physical backing memory where virtual memory will be mapped to</param>
         /// <param name="addressSpaceSize">Size of the address space</param>
         /// <param name="invalidAccessHandler">Optional function to handle invalid memory accesses</param>
-        public MemoryManager(ulong addressSpaceSize, InvalidAccessHandler invalidAccessHandler = null)
+        public MemoryManager(MemoryBlock backingMemory, ulong addressSpaceSize, InvalidAccessHandler invalidAccessHandler = null)
         {
+            _backingMemory = backingMemory;
             _invalidAccessHandler = invalidAccessHandler;
 
             ulong asSize = PageSize;
@@ -73,18 +76,19 @@ namespace Ryujinx.Cpu
         }
 
         /// <inheritdoc/>
-        public void Map(ulong va, nuint hostAddress, ulong size)
+        public void Map(ulong va, ulong pa, ulong size)
         {
             AssertValidAddressAndSize(va, size);
 
             ulong remainingSize = size;
             ulong oVa = va;
+            ulong oPa = pa;
             while (remainingSize != 0)
             {
-                _pageTable.Write((va / PageSize) * PteSize, hostAddress);
+                _pageTable.Write((va / PageSize) * PteSize, PaToPte(pa));
 
                 va += PageSize;
-                hostAddress += PageSize;
+                pa += PageSize;
                 remainingSize -= PageSize;
             }
             Tracking.Map(oVa, size);
@@ -107,7 +111,7 @@ namespace Ryujinx.Cpu
             ulong remainingSize = size;
             while (remainingSize != 0)
             {
-                _pageTable.Write((va / PageSize) * PteSize, (nuint)0);
+                _pageTable.Write((va / PageSize) * PteSize, 0UL);
 
                 va += PageSize;
                 remainingSize -= PageSize;
@@ -123,8 +127,21 @@ namespace Ryujinx.Cpu
         /// <inheritdoc/>
         public T ReadTracked<T>(ulong va) where T : unmanaged
         {
-            SignalMemoryTracking(va, (ulong)Unsafe.SizeOf<T>(), false);
-            return MemoryMarshal.Cast<byte, T>(GetSpan(va, Unsafe.SizeOf<T>()))[0];
+            try
+            {
+                SignalMemoryTracking(va, (ulong)Unsafe.SizeOf<T>(), false);
+
+                return Read<T>(va);
+            }
+            catch (InvalidMemoryRegionException)
+            {
+                if (_invalidAccessHandler == null || !_invalidAccessHandler(va))
+                {
+                    throw;
+                }
+
+                return default;
+            }
         }
 
         /// <inheritdoc/>
@@ -177,7 +194,7 @@ namespace Ryujinx.Cpu
 
                 if (IsContiguousAndMapped(va, data.Length))
                 {
-                    data.CopyTo(GetHostSpanContiguous(va, data.Length));
+                    data.CopyTo(_backingMemory.GetSpan(GetPhysicalAddressInternal(va), data.Length));
                 }
                 else
                 {
@@ -185,18 +202,22 @@ namespace Ryujinx.Cpu
 
                     if ((va & PageMask) != 0)
                     {
+                        ulong pa = GetPhysicalAddressInternal(va);
+
                         size = Math.Min(data.Length, PageSize - (int)(va & PageMask));
 
-                        data.Slice(0, size).CopyTo(GetHostSpanContiguous(va, size));
+                        data.Slice(0, size).CopyTo(_backingMemory.GetSpan(pa, size));
 
                         offset += size;
                     }
 
                     for (; offset < data.Length; offset += size)
                     {
+                        ulong pa = GetPhysicalAddressInternal(va + (ulong)offset);
+
                         size = Math.Min(data.Length - offset, PageSize);
 
-                        data.Slice(offset, size).CopyTo(GetHostSpanContiguous(va + (ulong)offset, size));
+                        data.Slice(offset, size).CopyTo(_backingMemory.GetSpan(pa, size));
                     }
                 }
             }
@@ -224,7 +245,7 @@ namespace Ryujinx.Cpu
 
             if (IsContiguousAndMapped(va, size))
             {
-                return GetHostSpanContiguous(va, size);
+                return _backingMemory.GetSpan(GetPhysicalAddressInternal(va), size);
             }
             else
             {
@@ -251,7 +272,7 @@ namespace Ryujinx.Cpu
                     SignalMemoryTracking(va, (ulong)size, true);
                 }
 
-                return new WritableRegion(null, va, new NativeMemoryManager<byte>((byte*)GetHostAddress(va), size).Memory);
+                return new WritableRegion(null, va, _backingMemory.GetMemory(GetPhysicalAddressInternal(va), size));
             }
             else
             {
@@ -264,7 +285,7 @@ namespace Ryujinx.Cpu
         }
 
         /// <inheritdoc/>
-        public unsafe ref T GetRef<T>(ulong va) where T : unmanaged
+        public ref T GetRef<T>(ulong va) where T : unmanaged
         {
             if (!IsContiguous(va, Unsafe.SizeOf<T>()))
             {
@@ -273,7 +294,7 @@ namespace Ryujinx.Cpu
 
             SignalMemoryTracking(va, (ulong)Unsafe.SizeOf<T>(), true);
 
-            return ref *(T*)GetHostAddress(va);
+            return ref _backingMemory.GetRef<T>(GetPhysicalAddressInternal(va));
         }
 
         /// <summary>
@@ -293,7 +314,7 @@ namespace Ryujinx.Cpu
             return (int)(vaSpan / PageSize);
         }
 
-        private void ThrowMemoryNotContiguous() => throw new MemoryNotContiguousException();
+        private static void ThrowMemoryNotContiguous() => throw new MemoryNotContiguousException();
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private bool IsContiguousAndMapped(ulong va, int size) => IsContiguous(va, size) && IsMapped(va);
@@ -315,7 +336,7 @@ namespace Ryujinx.Cpu
                     return false;
                 }
 
-                if (GetHostAddress(va) + PageSize != GetHostAddress(va + PageSize))
+                if (GetPhysicalAddressInternal(va) + PageSize != GetPhysicalAddressInternal(va + PageSize))
                 {
                     return false;
                 }
@@ -327,11 +348,11 @@ namespace Ryujinx.Cpu
         }
 
         /// <inheritdoc/>
-        public IEnumerable<HostMemoryRange> GetPhysicalRegions(ulong va, ulong size)
+        public IEnumerable<MemoryRange> GetPhysicalRegions(ulong va, ulong size)
         {
             if (size == 0)
             {
-                return Enumerable.Empty<HostMemoryRange>();
+                return Enumerable.Empty<MemoryRange>();
             }
 
             if (!ValidateAddress(va) || !ValidateAddressAndSize(va, size))
@@ -341,9 +362,9 @@ namespace Ryujinx.Cpu
 
             int pages = GetPagesCount(va, (uint)size, out va);
 
-            var regions = new List<HostMemoryRange>();
+            var regions = new List<MemoryRange>();
 
-            nuint regionStart = GetHostAddress(va);
+            ulong regionStart = GetPhysicalAddressInternal(va);
             ulong regionSize = PageSize;
 
             for (int page = 0; page < pages - 1; page++)
@@ -353,12 +374,12 @@ namespace Ryujinx.Cpu
                     return null;
                 }
 
-                nuint newHostAddress = GetHostAddress(va + PageSize);
+                ulong newPa = GetPhysicalAddressInternal(va + PageSize);
 
-                if (GetHostAddress(va) + PageSize != newHostAddress)
+                if (GetPhysicalAddressInternal(va) + PageSize != newPa)
                 {
-                    regions.Add(new HostMemoryRange(regionStart, regionSize));
-                    regionStart = newHostAddress;
+                    regions.Add(new MemoryRange(regionStart, regionSize));
+                    regionStart = newPa;
                     regionSize = 0;
                 }
 
@@ -366,7 +387,7 @@ namespace Ryujinx.Cpu
                 regionSize += PageSize;
             }
 
-            regions.Add(new HostMemoryRange(regionStart, regionSize));
+            regions.Add(new MemoryRange(regionStart, regionSize));
 
             return regions;
         }
@@ -386,18 +407,22 @@ namespace Ryujinx.Cpu
 
                 if ((va & PageMask) != 0)
                 {
+                    ulong pa = GetPhysicalAddressInternal(va);
+
                     size = Math.Min(data.Length, PageSize - (int)(va & PageMask));
 
-                    GetHostSpanContiguous(va, size).CopyTo(data.Slice(0, size));
+                    _backingMemory.GetSpan(pa, size).CopyTo(data.Slice(0, size));
 
                     offset += size;
                 }
 
                 for (; offset < data.Length; offset += size)
                 {
+                    ulong pa = GetPhysicalAddressInternal(va + (ulong)offset);
+
                     size = Math.Min(data.Length - offset, PageSize);
 
-                    GetHostSpanContiguous(va + (ulong)offset, size).CopyTo(data.Slice(offset, size));
+                    _backingMemory.GetSpan(pa, size).CopyTo(data.Slice(offset, size));
                 }
             }
             catch (InvalidMemoryRegionException)
@@ -446,7 +471,7 @@ namespace Ryujinx.Cpu
                 return false;
             }
 
-            return _pageTable.Read<nuint>((va / PageSize) * PteSize) != 0;
+            return _pageTable.Read<ulong>((va / PageSize) * PteSize) != 0;
         }
 
         private bool ValidateAddress(ulong va)
@@ -480,37 +505,20 @@ namespace Ryujinx.Cpu
             }
         }
 
-        /// <summary>
-        /// Get a span representing the given virtual address and size range in host memory.
-        /// This function assumes that the requested virtual memory region is contiguous.
-        /// </summary>
-        /// <param name="va">Virtual address of the range</param>
-        /// <param name="size">Size of the range in bytes</param>
-        /// <returns>A span representing the given virtual range in host memory</returns>
-        /// <exception cref="InvalidMemoryRegionException">Throw when the base virtual address is not mapped</exception>
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private unsafe Span<byte> GetHostSpanContiguous(ulong va, int size)
+        private ulong GetPhysicalAddress(ulong va)
         {
-            return new Span<byte>((void*)GetHostAddress(va), size);
-        }
-
-        /// <summary>
-        /// Get the host address for a given virtual address, using the page table.
-        /// </summary>
-        /// <param name="va">Virtual address</param>
-        /// <returns>The corresponding host address for the given virtual address</returns>
-        /// <exception cref="InvalidMemoryRegionException">Throw when the virtual address is not mapped</exception>
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        private nuint GetHostAddress(ulong va)
-        {
-            nuint pageBase = _pageTable.Read<nuint>((va / PageSize) * PteSize) & unchecked((nuint)0xffff_ffff_ffffUL);
-
-            if (pageBase == 0)
+            // We return -1L if the virtual address is invalid or unmapped.
+            if (!ValidateAddress(va) || !IsMapped(va))
             {
-                ThrowInvalidMemoryRegionException($"Not mapped: va=0x{va:X16}");
+                return ulong.MaxValue;
             }
 
-            return pageBase + (nuint)(va & PageMask);
+            return GetPhysicalAddressInternal(va);
+        }
+
+        private ulong GetPhysicalAddressInternal(ulong va)
+        {
+            return PteToPa(_pageTable.Read<ulong>((va / PageSize) * PteSize) & ~(0xffffUL << 48)) + (va & PageMask);
         }
 
         /// <inheritdoc/>
@@ -604,6 +612,16 @@ namespace Ryujinx.Cpu
             }
         }
 
+        private ulong PaToPte(ulong pa)
+        {
+            return (ulong)_backingMemory.GetPointer(pa, PageSize);
+        }
+
+        private ulong PteToPa(ulong pte)
+        {
+            return (ulong)((long)pte - _backingMemory.Pointer.ToInt64());
+        }
+
         /// <summary>
         /// Disposes of resources used by the memory manager.
         /// </summary>

Ryujinx.Cpu/MemoryManagerHostMapped.cs

@@ -5,7 +5,6 @@ using Ryujinx.Memory.Range;
 using Ryujinx.Memory.Tracking;
 using System;
 using System.Collections.Generic;
-using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Threading;
 
@@ -14,7 +13,7 @@ namespace Ryujinx.Cpu
     /// <summary>
     /// Represents a CPU memory manager which maps guest virtual memory directly onto a host virtual region.
     /// </summary>
-    public class MemoryManagerHostMapped : MemoryManagerBase, IMemoryManager, IVirtualMemoryManagerTracked
+    public class MemoryManagerHostMapped : MemoryManagerBase, IMemoryManager, IVirtualMemoryManagerTracked, IWritableBlock
     {
         public const int PageBits = 12;
         public const int PageSize = 1 << PageBits;
@@ -42,9 +41,12 @@ namespace Ryujinx.Cpu
         private readonly MemoryBlock _addressSpaceMirror;
         private readonly ulong _addressSpaceSize;
 
+        private readonly MemoryBlock _backingMemory;
+        private readonly PageTable<ulong> _pageTable;
+
         private readonly MemoryEhMeilleure _memoryEh;
 
-        private ulong[] _pageTable;
+        private readonly ulong[] _pageBitmap;
 
         public int AddressSpaceBits { get; }
 
@@ -59,11 +61,14 @@ namespace Ryujinx.Cpu
         /// <summary>
         /// Creates a new instance of the host mapped memory manager.
         /// </summary>
+        /// <param name="backingMemory">Physical backing memory where virtual memory will be mapped to</param>
         /// <param name="addressSpaceSize">Size of the address space</param>
         /// <param name="unsafeMode">True if unmanaged access should not be masked (unsafe), false otherwise.</param>
         /// <param name="invalidAccessHandler">Optional function to handle invalid memory accesses</param>
-        public MemoryManagerHostMapped(ulong addressSpaceSize, bool unsafeMode, InvalidAccessHandler invalidAccessHandler = null)
+        public MemoryManagerHostMapped(MemoryBlock backingMemory, ulong addressSpaceSize, bool unsafeMode, InvalidAccessHandler invalidAccessHandler = null)
         {
+            _backingMemory = backingMemory;
+            _pageTable = new PageTable<ulong>();
             _invalidAccessHandler = invalidAccessHandler;
             _unsafeMode = unsafeMode;
             _addressSpaceSize = addressSpaceSize;
@@ -79,9 +84,13 @@ namespace Ryujinx.Cpu
 
             AddressSpaceBits = asBits;
 
-            _pageTable = new ulong[1 << (AddressSpaceBits - (PageBits + PageToPteShift))];
-            _addressSpace = new MemoryBlock(asSize, MemoryAllocationFlags.Reserve | MemoryAllocationFlags.Mirrorable);
-            _addressSpaceMirror = _addressSpace.CreateMirror();
+            _pageBitmap = new ulong[1 << (AddressSpaceBits - (PageBits + PageToPteShift))];
+
+            MemoryAllocationFlags asFlags = MemoryAllocationFlags.Reserve | MemoryAllocationFlags.ViewCompatible;
+
+            _addressSpace = new MemoryBlock(asSize, asFlags);
+            _addressSpaceMirror = new MemoryBlock(asSize, asFlags | MemoryAllocationFlags.ForceWindows4KBViewMapping);
+
             Tracking = new MemoryTracking(this, PageSize, invalidAccessHandler);
             _memoryEh = new MemoryEhMeilleure(_addressSpace, Tracking);
         }
@@ -136,12 +145,14 @@ namespace Ryujinx.Cpu
         }
 
         /// <inheritdoc/>
-        public void Map(ulong va, nuint hostAddress, ulong size)
+        public void Map(ulong va, ulong pa, ulong size)
         {
             AssertValidAddressAndSize(va, size);
 
-            _addressSpace.Commit(va, size);
+            _addressSpace.MapView(_backingMemory, pa, va, size);
+            _addressSpaceMirror.MapView(_backingMemory, pa, va, size);
             AddMapping(va, size);
+            PtMap(va, pa, size);
 
             Tracking.Map(va, size);
         }
@@ -155,7 +166,32 @@ namespace Ryujinx.Cpu
             Tracking.Unmap(va, size);
 
             RemoveMapping(va, size);
-            _addressSpace.Decommit(va, size);
+            PtUnmap(va, size);
+            _addressSpace.UnmapView(_backingMemory, va, size);
+            _addressSpaceMirror.UnmapView(_backingMemory, va, size);
+        }
+
+        private void PtMap(ulong va, ulong pa, ulong size)
+        {
+            while (size != 0)
+            {
+                _pageTable.Map(va, pa);
+
+                va += PageSize;
+                pa += PageSize;
+                size -= PageSize;
+            }
+        }
+
+        private void PtUnmap(ulong va, ulong size)
+        {
+            while (size != 0)
+            {
+                _pageTable.Unmap(va);
+
+                va += PageSize;
+                size -= PageSize;
+            }
         }
 
         /// <inheritdoc/>
@@ -216,6 +252,7 @@ namespace Ryujinx.Cpu
             }
         }
 
+
         /// <inheritdoc/>
         public void Write<T>(ulong va, T value) where T : unmanaged
         {
@@ -267,7 +304,7 @@ namespace Ryujinx.Cpu
                     throw;
                 }
             }
-}
+        }
 
         /// <inheritdoc/>
         public ReadOnlySpan<byte> GetSpan(ulong va, int size, bool tracked = false)
@@ -322,7 +359,7 @@ namespace Ryujinx.Cpu
             int bit = (int)((page & 31) << 1);
 
             int pageIndex = (int)(page >> PageToPteShift);
-            ref ulong pageRef = ref _pageTable[pageIndex];
+            ref ulong pageRef = ref _pageBitmap[pageIndex];
 
             ulong pte = Volatile.Read(ref pageRef);
 
@@ -373,7 +410,7 @@ namespace Ryujinx.Cpu
                     mask &= endMask;
                 }
 
-                ref ulong pageRef = ref _pageTable[pageIndex++];
+                ref ulong pageRef = ref _pageBitmap[pageIndex++];
                 ulong pte = Volatile.Read(ref pageRef);
 
                 pte |= pte >> 1;
@@ -389,16 +426,53 @@ namespace Ryujinx.Cpu
         }
 
         /// <inheritdoc/>
-        public IEnumerable<HostMemoryRange> GetPhysicalRegions(ulong va, ulong size)
+        public IEnumerable<MemoryRange> GetPhysicalRegions(ulong va, ulong size)
         {
-            if (size == 0)
+            int pages = GetPagesCount(va, (uint)size, out va);
+
+            var regions = new List<MemoryRange>();
+
+            ulong regionStart = GetPhysicalAddressChecked(va);
+            ulong regionSize = PageSize;
+
+            for (int page = 0; page < pages - 1; page++)
             {
-                return Enumerable.Empty<HostMemoryRange>();
+                if (!ValidateAddress(va + PageSize))
+                {
+                    return null;
+                }
+
+                ulong newPa = GetPhysicalAddressChecked(va + PageSize);
+
+                if (GetPhysicalAddressChecked(va) + PageSize != newPa)
+                {
+                    regions.Add(new MemoryRange(regionStart, regionSize));
+                    regionStart = newPa;
+                    regionSize = 0;
+                }
+
+                va += PageSize;
+                regionSize += PageSize;
             }
 
-            AssertMapped(va, size);
+            regions.Add(new MemoryRange(regionStart, regionSize));
 
-            return new HostMemoryRange[] { new HostMemoryRange(_addressSpaceMirror.GetPointer(va, size), size) };
+            return regions;
+        }
+
+        private ulong GetPhysicalAddressChecked(ulong va)
+        {
+            if (!IsMapped(va))
+            {
+                ThrowInvalidMemoryRegionException($"Not mapped: va=0x{va:X16}");
+            }
+
+            return GetPhysicalAddressInternal(va);
+        }
+
+        private ulong GetPhysicalAddressInternal(ulong va)
+        {
+            return _pageTable.Read(va) + (va & PageMask);
         }
 
         /// <inheritdoc/>
@@ -427,7 +501,7 @@ namespace Ryujinx.Cpu
                 int bit = (int)((pageStart & 31) << 1);
 
                 int pageIndex = (int)(pageStart >> PageToPteShift);
-                ref ulong pageRef = ref _pageTable[pageIndex];
+                ref ulong pageRef = ref _pageBitmap[pageIndex];
 
                 ulong pte = Volatile.Read(ref pageRef);
                 ulong state = ((pte >> bit) & 3);
@@ -459,7 +533,7 @@ namespace Ryujinx.Cpu
                         mask &= endMask;
                     }
 
-                    ref ulong pageRef = ref _pageTable[pageIndex++];
+                    ref ulong pageRef = ref _pageBitmap[pageIndex++];
 
                     ulong pte = Volatile.Read(ref pageRef);
                     ulong mappedMask = mask & BlockMappedMask;
@@ -530,7 +604,7 @@ namespace Ryujinx.Cpu
                 ulong tag = protTag << bit;
 
                 int pageIndex = (int)(pageStart >> PageToPteShift);
-                ref ulong pageRef = ref _pageTable[pageIndex];
+                ref ulong pageRef = ref _pageBitmap[pageIndex];
 
                 ulong pte;
 
@@ -562,7 +636,7 @@ namespace Ryujinx.Cpu
                         mask &= endMask;
                     }
 
-                    ref ulong pageRef = ref _pageTable[pageIndex++];
+                    ref ulong pageRef = ref _pageBitmap[pageIndex++];
 
                     ulong pte;
                     ulong mappedMask;
@@ -632,7 +706,7 @@ namespace Ryujinx.Cpu
                     mask &= endMask;
                 }
 
-                ref ulong pageRef = ref _pageTable[pageIndex++];
+                ref ulong pageRef = ref _pageBitmap[pageIndex++];
 
                 ulong pte;
                 ulong mappedMask;
@@ -677,7 +751,7 @@ namespace Ryujinx.Cpu
                     mask |= endMask;
                 }
 
-                ref ulong pageRef = ref _pageTable[pageIndex++];
+                ref ulong pageRef = ref _pageBitmap[pageIndex++];
                 ulong pte;
 
                 do
@@ -695,11 +769,11 @@ namespace Ryujinx.Cpu
         /// </summary>
         protected override void Destroy()
         {
-            _addressSpaceMirror.Dispose();
             _addressSpace.Dispose();
+            _addressSpaceMirror.Dispose();
             _memoryEh.Dispose();
         }
 
-        private void ThrowInvalidMemoryRegionException(string message) => throw new InvalidMemoryRegionException(message);
+        private static void ThrowInvalidMemoryRegionException(string message) => throw new InvalidMemoryRegionException(message);
     }
 }

Ryujinx.HLE/HOS/ApplicationLoader.cs

@@ -17,6 +17,7 @@ using Ryujinx.Common.Logging;
 using Ryujinx.HLE.FileSystem;
 using Ryujinx.HLE.HOS.Kernel.Process;
 using Ryujinx.HLE.Loaders.Executables;
+using Ryujinx.Memory;
 using System;
 using System.Collections.Generic;
 using System.Globalization;
@@ -561,7 +562,14 @@ namespace Ryujinx.HLE.HOS
             Graphics.Gpu.GraphicsConfig.TitleId = TitleIdText;
             _device.Gpu.HostInitalized.Set();
 
-            Ptc.Initialize(TitleIdText, DisplayVersion, usePtc, _device.Configuration.MemoryManagerMode);
+            MemoryManagerMode memoryManagerMode = _device.Configuration.MemoryManagerMode;
+
+            if (!MemoryBlock.SupportsFlags(MemoryAllocationFlags.ViewCompatible))
+            {
+                memoryManagerMode = MemoryManagerMode.SoftwarePageTable;
+            }
+
+            Ptc.Initialize(TitleIdText, DisplayVersion, usePtc, memoryManagerMode);
 
             metaData.GetNpdm(out Npdm npdm).ThrowIfFailure();
             ProgramLoader.LoadNsos(_device.System.KernelContext, out ProcessTamperInfo tamperInfo, metaData, new ProgramInfo(in npdm), executables: programs);

Ryujinx.HLE/HOS/ArmProcessContextFactory.cs

@@ -21,15 +21,20 @@ namespace Ryujinx.HLE.HOS
         {
             MemoryManagerMode mode = context.Device.Configuration.MemoryManagerMode;
 
+            if (!MemoryBlock.SupportsFlags(MemoryAllocationFlags.ViewCompatible))
+            {
+                mode = MemoryManagerMode.SoftwarePageTable;
+            }
+
             switch (mode)
             {
                 case MemoryManagerMode.SoftwarePageTable:
-                    return new ArmProcessContext<MemoryManager>(pid, _gpu, new MemoryManager(addressSpaceSize, invalidAccessHandler), for64Bit);
+                    return new ArmProcessContext<MemoryManager>(pid, _gpu, new MemoryManager(context.Memory, addressSpaceSize, invalidAccessHandler), for64Bit);
 
                 case MemoryManagerMode.HostMapped:
                 case MemoryManagerMode.HostMappedUnsafe:
                     bool unsafeMode = mode == MemoryManagerMode.HostMappedUnsafe;
-                    return new ArmProcessContext<MemoryManagerHostMapped>(pid, _gpu, new MemoryManagerHostMapped(addressSpaceSize, unsafeMode, invalidAccessHandler), for64Bit);
+                    return new ArmProcessContext<MemoryManagerHostMapped>(pid, _gpu, new MemoryManagerHostMapped(context.Memory, addressSpaceSize, unsafeMode, invalidAccessHandler), for64Bit);
 
                 default:
                     throw new ArgumentOutOfRangeException();

Ryujinx.HLE/HOS/Kernel/Memory/KPageTable.cs

@@ -1,10 +1,7 @@
 using Ryujinx.HLE.HOS.Kernel.Common;
 using Ryujinx.Memory;
-using Ryujinx.Memory.Range;
 using System;
-using System.Collections.Generic;
 using System.Diagnostics;
-using System.Linq;
 
 namespace Ryujinx.HLE.HOS.Kernel.Memory
 {
@@ -12,17 +9,19 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
     {
         private readonly IVirtualMemoryManager _cpuMemory;
 
-        public override bool SupportsMemoryAliasing => true;
-
         public KPageTable(KernelContext context, IVirtualMemoryManager cpuMemory) : base(context)
         {
             _cpuMemory = cpuMemory;
         }
 
         /// <inheritdoc/>
-        protected override IEnumerable<HostMemoryRange> GetPhysicalRegions(ulong va, ulong size)
+        protected override void GetPhysicalRegions(ulong va, ulong size, KPageList pageList)
         {
-            return _cpuMemory.GetPhysicalRegions(va, size);
+            var ranges = _cpuMemory.GetPhysicalRegions(va, size);
+            foreach (var range in ranges)
+            {
+                pageList.AddRange(range.Address + DramMemoryMap.DramBase, range.Size / PageSize);
+            }
         }
 
         /// <inheritdoc/>
@@ -34,7 +33,8 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
         /// <inheritdoc/>
         protected override KernelResult MapMemory(ulong src, ulong dst, ulong pagesCount, KMemoryPermission oldSrcPermission, KMemoryPermission newDstPermission)
         {
-            var srcRanges = GetPhysicalRegions(src, pagesCount * PageSize);
+            KPageList pageList = new KPageList();
+            GetPhysicalRegions(src, pagesCount * PageSize, pageList);
 
             KernelResult result = Reprotect(src, pagesCount, KMemoryPermission.None);
 
@@ -43,7 +43,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
                 return result;
             }
 
-            result = MapPages(dst, srcRanges, newDstPermission);
+            result = MapPages(dst, pageList, newDstPermission, false, 0);
 
             if (result != KernelResult.Success)
             {
@@ -59,10 +59,13 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
         {
             ulong size = pagesCount * PageSize;
 
-            var srcRanges = GetPhysicalRegions(src, size);
-            var dstRanges = GetPhysicalRegions(dst, size);
+            KPageList srcPageList = new KPageList();
+            KPageList dstPageList = new KPageList();
 
-            if (!dstRanges.SequenceEqual(srcRanges))
+            GetPhysicalRegions(src, size, srcPageList);
+            GetPhysicalRegions(dst, size, dstPageList);
+
+            if (!dstPageList.IsEqual(srcPageList))
             {
                 return KernelResult.InvalidMemRange;
             }
@@ -78,7 +81,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
 
             if (result != KernelResult.Success)
             {
-                KernelResult mapResult = MapPages(dst, dstRanges, oldDstPermission);
+                KernelResult mapResult = MapPages(dst, dstPageList, oldDstPermission, false, 0);
                 Debug.Assert(mapResult == KernelResult.Success);
             }
 
@@ -92,7 +95,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
 
             Context.Memory.Commit(srcPa - DramMemoryMap.DramBase, size);
 
-            _cpuMemory.Map(dstVa, Context.Memory.GetPointer(srcPa - DramMemoryMap.DramBase, size), size);
+            _cpuMemory.Map(dstVa, srcPa - DramMemoryMap.DramBase, size);
 
             if (DramMemoryMap.IsHeapPhysicalAddress(srcPa))
             {
@@ -121,7 +124,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
 
                 Context.Memory.Commit(addr, size);
 
-                _cpuMemory.Map(currentVa, Context.Memory.GetPointer(addr, size), size);
+                _cpuMemory.Map(currentVa, addr, size);
 
                 if (shouldFillPages)
                 {
@@ -136,33 +139,6 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
             return KernelResult.Success;
         }
 
-        /// <inheritdoc/>
-        protected override KernelResult MapPages(ulong address, IEnumerable<HostMemoryRange> ranges, KMemoryPermission permission)
-        {
-            ulong currentVa = address;
-
-            foreach (var range in ranges)
-            {
-                ulong size = range.Size;
-
-                ulong pa = GetDramAddressFromHostAddress(range.Address);
-                if (pa != ulong.MaxValue)
-                {
-                    pa += DramMemoryMap.DramBase;
-                    if (DramMemoryMap.IsHeapPhysicalAddress(pa))
-                    {
-                        Context.MemoryManager.IncrementPagesReferenceCount(pa, size / PageSize);
-                    }
-                }
-
-                _cpuMemory.Map(currentVa, range.Address, size);
-
-                currentVa += size;
-            }
-
-            return KernelResult.Success;
-        }
-
         /// <inheritdoc/>
         protected override KernelResult Unmap(ulong address, ulong pagesCount)
         {
@@ -172,13 +148,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
 
             foreach (var region in regions)
             {
-                ulong pa = GetDramAddressFromHostAddress(region.Address);
-                if (pa == ulong.MaxValue)
-                {
-                    continue;
-                }
-
-                pa += DramMemoryMap.DramBase;
+                ulong pa = region.Address + DramMemoryMap.DramBase;
                 if (DramMemoryMap.IsHeapPhysicalAddress(pa))
                 {
                     pagesToClose.AddRange(pa, region.Size / PageSize);
@@ -217,15 +187,5 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
         {
             _cpuMemory.Write(va, data);
         }
-
-        private ulong GetDramAddressFromHostAddress(nuint hostAddress)
-        {
-            if (hostAddress < (nuint)(ulong)Context.Memory.Pointer || hostAddress >= (nuint)((ulong)Context.Memory.Pointer + Context.Memory.Size))
-            {
-                return ulong.MaxValue;
-            }
-
-            return hostAddress - (ulong)Context.Memory.Pointer;
-        }
     }
 }

Ryujinx.HLE/HOS/Kernel/Memory/KPageTableBase.cs

@@ -1,11 +1,9 @@
 using Ryujinx.Common;
 using Ryujinx.HLE.HOS.Kernel.Common;
 using Ryujinx.HLE.HOS.Kernel.Process;
-using Ryujinx.Memory.Range;
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
-using System.Linq;
 
 namespace Ryujinx.HLE.HOS.Kernel.Memory
 {
@@ -73,8 +71,6 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
 
         private MersenneTwister _randomNumberGenerator;
 
-        public abstract bool SupportsMemoryAliasing { get; }
-
         private MemoryFillValue _heapFillValue;
         private MemoryFillValue _ipcFillValue;
 
@@ -305,7 +301,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
             TlsIoRegionStart = tlsIoRegion.Start;
             TlsIoRegionEnd = tlsIoRegion.End;
 
-            // TODO: Check kernel configuration via secure monitor call when implemented to set memory fill values. 
+            // TODO: Check kernel configuration via secure monitor call when implemented to set memory fill values.
 
             _currentHeapAddr = HeapRegionStart;
             _heapCapacity = 0;
@@ -380,8 +376,9 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
             }
         }
 
-        public KernelResult UnmapPages(ulong address, ulong pagesCount, IEnumerable<HostMemoryRange> ranges, MemoryState stateExpected)
+        public KernelResult UnmapPages(ulong address, KPageList pageList, MemoryState stateExpected)
         {
+            ulong pagesCount = pageList.GetPagesCount();
             ulong size = pagesCount * PageSize;
 
             ulong endAddr = address + size;
@@ -405,9 +402,11 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
 
             lock (_blockManager)
             {
-                var currentRanges = GetPhysicalRegions(address, size);
+                KPageList currentPageList = new KPageList();
 
-                if (!currentRanges.SequenceEqual(ranges))
+                GetPhysicalRegions(address, size, currentPageList);
+
+                if (!currentPageList.IsEqual(pageList))
                 {
                     return KernelResult.InvalidMemRange;
                 }
@@ -1690,11 +1689,6 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
             bool send,
             out ulong dst)
         {
-            if (!SupportsMemoryAliasing)
-            {
-                throw new NotSupportedException("Memory aliasing not supported, can't map IPC buffers.");
-            }
-
             dst = 0;
 
             if (!_slabManager.CanAllocate(MaxBlocksNeededForInsertion))
@@ -1828,7 +1822,10 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
             {
                 ulong alignedSize = endAddrTruncated - addressRounded;
 
-                KernelResult result = MapPages(currentVa, srcPageTable.GetPhysicalRegions(addressRounded, alignedSize), permission);
+                KPageList pageList = new KPageList();
+                srcPageTable.GetPhysicalRegions(addressRounded, alignedSize, pageList);
+
+                KernelResult result = MapPages(currentVa, pageList, permission);
 
                 if (result != KernelResult.Success)
                 {
@@ -2041,7 +2038,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
                 MemoryAttribute.Borrowed);
         }
 
-        public KernelResult BorrowTransferMemory(List<HostMemoryRange> ranges, ulong address, ulong size, KMemoryPermission permission)
+        public KernelResult BorrowTransferMemory(KPageList pageList, ulong address, ulong size, KMemoryPermission permission)
         {
             return SetAttributesAndChangePermission(
                 address,
@@ -2054,7 +2051,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
                 MemoryAttribute.None,
                 permission,
                 MemoryAttribute.Borrowed,
-                ranges);
+                pageList);
         }
 
         private KernelResult SetAttributesAndChangePermission(
@@ -2068,7 +2065,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
             MemoryAttribute attributeExpected,
             KMemoryPermission newPermission,
             MemoryAttribute attributeSetMask,
-            List<HostMemoryRange> ranges = null)
+            KPageList pageList = null)
         {
             if (address + size <= address || !InsideAddrSpace(address, size))
             {
@@ -2093,7 +2090,10 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
                 {
                     ulong pagesCount = size / PageSize;
 
-                    ranges?.AddRange(GetPhysicalRegions(address, size));
+                    if (pageList != null)
+                    {
+                        GetPhysicalRegions(address, pagesCount * PageSize, pageList);
+                    }
 
                     if (!_slabManager.CanAllocate(MaxBlocksNeededForInsertion))
                     {
@@ -2143,7 +2143,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
                 MemoryAttribute.Borrowed);
         }
 
-        public KernelResult UnborrowTransferMemory(ulong address, ulong size, List<HostMemoryRange> ranges)
+        public KernelResult UnborrowTransferMemory(ulong address, ulong size, KPageList pageList)
         {
             return ClearAttributesAndChangePermission(
                 address,
@@ -2156,7 +2156,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
                 MemoryAttribute.Borrowed,
                 KMemoryPermission.ReadAndWrite,
                 MemoryAttribute.Borrowed,
-                ranges);
+                pageList);
         }
 
         private KernelResult ClearAttributesAndChangePermission(
@@ -2170,7 +2170,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
             MemoryAttribute attributeExpected,
             KMemoryPermission newPermission,
             MemoryAttribute attributeClearMask,
-            List<HostMemoryRange> ranges = null)
+            KPageList pageList = null)
         {
             if (address + size <= address || !InsideAddrSpace(address, size))
             {
@@ -2195,11 +2195,13 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
                 {
                     ulong pagesCount = size / PageSize;
 
-                    if (ranges != null)
+                    if (pageList != null)
                     {
-                        var currentRanges = GetPhysicalRegions(address, size);
+                        KPageList currentPageList = new KPageList();
 
-                        if (!currentRanges.SequenceEqual(ranges))
+                        GetPhysicalRegions(address, pagesCount * PageSize, currentPageList);
+
+                        if (!currentPageList.IsEqual(pageList))
                         {
                             return KernelResult.InvalidMemRange;
                         }
@@ -2741,8 +2743,8 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
         /// </summary>
         /// <param name="va">Virtual address of the range</param>
         /// <param name="size">Size of the range</param>
-        /// <returns>Array of physical regions</returns>
-        protected abstract IEnumerable<HostMemoryRange> GetPhysicalRegions(ulong va, ulong size);
+        /// <param name="pageList">Page list where the ranges will be added</param>
+        protected abstract void GetPhysicalRegions(ulong va, ulong size, KPageList pageList);
 
         /// <summary>
         /// Gets a read-only span of data from CPU mapped memory.
@@ -2803,16 +2805,6 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
         /// <returns>Result of the mapping operation</returns>
         protected abstract KernelResult MapPages(ulong address, KPageList pageList, KMemoryPermission permission, bool shouldFillPages = false, byte fillValue = 0);
 
-        /// <summary>
-        /// Maps a region of memory into the specified host memory ranges.
-        /// </summary>
-        /// <param name="address">Destination virtual address that should be mapped</param>
-        /// <param name="ranges">Ranges of host memory that should be mapped</param>
-        /// <param name="permission">Permission of the region to be mapped</param>
-        /// <returns>Result of the mapping operation</returns>
-        /// <exception cref="NotSupportedException">The implementation does not support memory aliasing</exception>
-        protected abstract KernelResult MapPages(ulong address, IEnumerable<HostMemoryRange> ranges, KMemoryPermission permission);
-
         /// <summary>
         /// Unmaps a region of memory that was previously mapped with one of the page mapping methods.
         /// </summary>

Ryujinx.HLE/HOS/Kernel/Memory/KPageTableHostMapped.cs

@@ -1,139 +0,0 @@
-using Ryujinx.HLE.HOS.Kernel.Common;
-using Ryujinx.Memory;
-using Ryujinx.Memory.Range;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-
-namespace Ryujinx.HLE.HOS.Kernel.Memory
-{
-    class KPageTableHostMapped : KPageTableBase
-    {
-        private const int CopyChunckSize = 0x100000;
-
-        private readonly IVirtualMemoryManager _cpuMemory;
-
-        public override bool SupportsMemoryAliasing => false;
-
-        public KPageTableHostMapped(KernelContext context, IVirtualMemoryManager cpuMemory) : base(context)
-        {
-            _cpuMemory = cpuMemory;
-        }
-
-        /// <inheritdoc/>
-        protected override IEnumerable<HostMemoryRange> GetPhysicalRegions(ulong va, ulong size)
-        {
-            return _cpuMemory.GetPhysicalRegions(va, size);
-        }
-
-        /// <inheritdoc/>
-        protected override ReadOnlySpan<byte> GetSpan(ulong va, int size)
-        {
-            return _cpuMemory.GetSpan(va, size);
-        }
-
-        /// <inheritdoc/>
-        protected override KernelResult MapMemory(ulong src, ulong dst, ulong pagesCount, KMemoryPermission oldSrcPermission, KMemoryPermission newDstPermission)
-        {
-            ulong size = pagesCount * PageSize;
-
-            _cpuMemory.Map(dst, 0, size);
-
-            ulong currentSize = size;
-            while (currentSize > 0)
-            {
-                ulong copySize = Math.Min(currentSize, CopyChunckSize);
-                _cpuMemory.Write(dst, _cpuMemory.GetSpan(src, (int)copySize));
-                currentSize -= copySize;
-            }
-
-            return KernelResult.Success;
-        }
-
-        /// <inheritdoc/>
-        protected override KernelResult UnmapMemory(ulong dst, ulong src, ulong pagesCount, KMemoryPermission oldDstPermission, KMemoryPermission newSrcPermission)
-        {
-            ulong size = pagesCount * PageSize;
-
-            // TODO: Validation.
-
-            ulong currentSize = size;
-            while (currentSize > 0)
-            {
-                ulong copySize = Math.Min(currentSize, CopyChunckSize);
-                _cpuMemory.Write(src, _cpuMemory.GetSpan(dst, (int)copySize));
-                currentSize -= copySize;
-            }
-
-            _cpuMemory.Unmap(dst, size);
-            return KernelResult.Success;
-        }
-
-        /// <inheritdoc/>
-        protected override KernelResult MapPages(ulong dstVa, ulong pagesCount, ulong srcPa, KMemoryPermission permission, bool shouldFillPages, byte fillValue)
-        {
-            _cpuMemory.Map(dstVa, 0, pagesCount * PageSize);
-
-            if (shouldFillPages)
-            {
-                _cpuMemory.Fill(dstVa, pagesCount * PageSize, fillValue);
-            }
-
-            return KernelResult.Success;
-        }
-
-        /// <inheritdoc/>
-        protected override KernelResult MapPages(ulong address, KPageList pageList, KMemoryPermission permission, bool shouldFillPages, byte fillValue)
-        {
-            ulong pagesCount = pageList.GetPagesCount();
-
-            _cpuMemory.Map(address, 0, pagesCount * PageSize);
-
-            if (shouldFillPages)
-            {
-                _cpuMemory.Fill(address, pagesCount * PageSize, fillValue);
-            }
-
-            return KernelResult.Success;
-        }
-
-        /// <inheritdoc/>
-        protected override KernelResult MapPages(ulong address, IEnumerable<HostMemoryRange> ranges, KMemoryPermission permission)
-        {
-            throw new NotSupportedException();
-        }
-
-        /// <inheritdoc/>
-        protected override KernelResult Unmap(ulong address, ulong pagesCount)
-        {
-            _cpuMemory.Unmap(address, pagesCount * PageSize);
-            return KernelResult.Success;
-        }
-
-        /// <inheritdoc/>
-        protected override KernelResult Reprotect(ulong address, ulong pagesCount, KMemoryPermission permission)
-        {
-            // TODO.
-            return KernelResult.Success;
-        }
-
-        /// <inheritdoc/>
-        protected override KernelResult ReprotectWithAttributes(ulong address, ulong pagesCount, KMemoryPermission permission)
-        {
-            // TODO.
-            return KernelResult.Success;
-        }
-
-        /// <inheritdoc/>
-        protected override void SignalMemoryTracking(ulong va, ulong size, bool write)
-        {
-            _cpuMemory.SignalMemoryTracking(va, size, write);
-        }
-
-        /// <inheritdoc/>
-        protected override void Write(ulong va, ReadOnlySpan<byte> data)
-        {
-            _cpuMemory.Write(va, data);
-        }
-    }
-}

Ryujinx.HLE/HOS/Kernel/Memory/KSharedMemory.cs

@@ -6,7 +6,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
 {
     class KSharedMemory : KAutoObject
     {
-        private readonly SharedMemoryStorage _storage;
+        private readonly KPageList _pageList;
 
         private readonly ulong _ownerPid;
 
@@ -20,7 +20,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
             KMemoryPermission ownerPermission,
             KMemoryPermission userPermission) : base(context)
         {
-            _storage = storage;
+            _pageList = storage.GetPageList();
             _ownerPid = ownerPid;
             _ownerPermission = ownerPermission;
             _userPermission = userPermission;
@@ -33,10 +33,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
             KProcess process,
             KMemoryPermission permission)
         {
-            ulong pagesCountRounded = BitUtils.DivRoundUp(size, KPageTableBase.PageSize);
-
-            var pageList = _storage.GetPageList();
-            if (pageList.GetPagesCount() != pagesCountRounded)
+            if (_pageList.GetPagesCount() != BitUtils.DivRoundUp(size, KPageTableBase.PageSize))
             {
                 return KernelResult.InvalidSize;
             }
@@ -50,35 +47,17 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
                 return KernelResult.InvalidPermission;
             }
 
-            KernelResult result = memoryManager.MapPages(address, pageList, MemoryState.SharedMemory, permission);
-
-            if (result == KernelResult.Success && !memoryManager.SupportsMemoryAliasing)
-            {
-                _storage.Borrow(process, address);
-            }
-
-            return result;
+            return memoryManager.MapPages(address, _pageList, MemoryState.SharedMemory, permission);
         }
 
-        public KernelResult UnmapFromProcess(
-            KPageTableBase memoryManager,
-            ulong address,
-            ulong size,
-            KProcess process)
+        public KernelResult UnmapFromProcess(KPageTableBase memoryManager, ulong address, ulong size, KProcess process)
         {
-            ulong pagesCountRounded = BitUtils.DivRoundUp(size, KPageTableBase.PageSize);
-
-            var pageList = _storage.GetPageList();
-            ulong pagesCount = pageList.GetPagesCount();
-
-            if (pagesCount != pagesCountRounded)
+            if (_pageList.GetPagesCount() != BitUtils.DivRoundUp(size, KPageTableBase.PageSize))
             {
                 return KernelResult.InvalidSize;
             }
 
-            var ranges = _storage.GetRanges();
-
-            return memoryManager.UnmapPages(address, pagesCount, ranges, MemoryState.SharedMemory);
+            return memoryManager.UnmapPages(address, _pageList, MemoryState.SharedMemory);
         }
     }
 }

Ryujinx.HLE/HOS/Kernel/Memory/KTransferMemory.cs

@@ -1,9 +1,7 @@
 using Ryujinx.Common;
 using Ryujinx.HLE.HOS.Kernel.Common;
 using Ryujinx.HLE.HOS.Kernel.Process;
-using Ryujinx.Memory.Range;
 using System;
-using System.Collections.Generic;
 
 namespace Ryujinx.HLE.HOS.Kernel.Memory
 {
@@ -14,9 +12,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
         // TODO: Remove when we no longer need to read it from the owner directly.
         public KProcess Creator => _creator;
 
-        private readonly List<HostMemoryRange> _ranges;
-
-        private readonly SharedMemoryStorage _storage;
+        private readonly KPageList _pageList;
 
         public ulong Address { get; private set; }
         public ulong Size { get; private set; }
@@ -28,12 +24,12 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
 
         public KTransferMemory(KernelContext context) : base(context)
         {
-            _ranges = new List<HostMemoryRange>();
+            _pageList = new KPageList();
         }
 
         public KTransferMemory(KernelContext context, SharedMemoryStorage storage) : base(context)
         {
-            _storage = storage;
+            _pageList = storage.GetPageList();
             Permission = KMemoryPermission.ReadAndWrite;
 
             _hasBeenInitialized = true;
@@ -46,7 +42,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
 
             _creator = creator;
 
-            KernelResult result = creator.MemoryManager.BorrowTransferMemory(_ranges, address, size, permission);
+            KernelResult result = creator.MemoryManager.BorrowTransferMemory(_pageList, address, size, permission);
 
             if (result != KernelResult.Success)
             {
@@ -71,15 +67,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
             KProcess process,
             KMemoryPermission permission)
         {
-            if (_storage == null)
-            {
-                throw new NotImplementedException();
-            }
-
-            ulong pagesCountRounded = BitUtils.DivRoundUp(size, KPageTableBase.PageSize);
-
-            var pageList = _storage.GetPageList();
-            if (pageList.GetPagesCount() != pagesCountRounded)
+            if (_pageList.GetPagesCount() != BitUtils.DivRoundUp(size, KPageTableBase.PageSize))
             {
                 return KernelResult.InvalidSize;
             }
@@ -91,16 +79,11 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
 
             MemoryState state = Permission == KMemoryPermission.None ? MemoryState.TransferMemoryIsolated : MemoryState.TransferMemory;
 
-            KernelResult result = memoryManager.MapPages(address, pageList, state, KMemoryPermission.ReadAndWrite);
+            KernelResult result = memoryManager.MapPages(address, _pageList, state, KMemoryPermission.ReadAndWrite);
 
             if (result == KernelResult.Success)
             {
                 _isMapped = true;
-
-                if (!memoryManager.SupportsMemoryAliasing)
-                {
-                    _storage.Borrow(process, address);
-                }
             }
 
             return result;
@@ -112,26 +95,14 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
             ulong size,
             KProcess process)
         {
-            if (_storage == null)
-            {
-                throw new NotImplementedException();
-            }
-
-            ulong pagesCountRounded = BitUtils.DivRoundUp(size, KPageTableBase.PageSize);
-
-            var pageList = _storage.GetPageList();
-            ulong pagesCount = pageList.GetPagesCount();
-
-            if (pagesCount != pagesCountRounded)
+            if (_pageList.GetPagesCount() != BitUtils.DivRoundUp(size, KPageTableBase.PageSize))
             {
                 return KernelResult.InvalidSize;
             }
 
-            var ranges = _storage.GetRanges();
-
             MemoryState state = Permission == KMemoryPermission.None ? MemoryState.TransferMemoryIsolated : MemoryState.TransferMemory;
 
-            KernelResult result = memoryManager.UnmapPages(address, pagesCount, ranges, state);
+            KernelResult result = memoryManager.UnmapPages(address, _pageList, state);
 
             if (result == KernelResult.Success)
             {
@@ -145,7 +116,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
         {
             if (_hasBeenInitialized)
             {
-                if (!_isMapped && _creator.MemoryManager.UnborrowTransferMemory(Address, Size, _ranges) != KernelResult.Success)
+                if (!_isMapped && _creator.MemoryManager.UnborrowTransferMemory(Address, Size, _pageList) != KernelResult.Success)
                 {
                     throw new InvalidOperationException("Unexpected failure restoring transfer memory attributes.");
                 }

Ryujinx.HLE/HOS/Kernel/Memory/SharedMemoryStorage.cs

@@ -1,8 +1,4 @@
-using Ryujinx.HLE.HOS.Kernel.Process;
-using Ryujinx.Memory;
-using Ryujinx.Memory.Range;
-using System;
-using System.Collections.Generic;
+using System;
 
 namespace Ryujinx.HLE.HOS.Kernel.Memory
 {
@@ -12,9 +8,6 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
         private readonly KPageList _pageList;
         private readonly ulong _size;
 
-        private IVirtualMemoryManager _borrowerMemory;
-        private ulong _borrowerVa;
-
         public SharedMemoryStorage(KernelContext context, KPageList pageList)
         {
             _context = context;
@@ -29,24 +22,6 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
             }
         }
 
-        public void Borrow(KProcess dstProcess, ulong va)
-        {
-            ulong currentOffset = 0;
-
-            foreach (KPageNode pageNode in _pageList)
-            {
-                ulong address = pageNode.Address - DramMemoryMap.DramBase;
-                ulong size = pageNode.PagesCount * KPageTableBase.PageSize;
-
-                dstProcess.CpuMemory.Write(va + currentOffset, _context.Memory.GetSpan(address + currentOffset, (int)size));
-
-                currentOffset += size;
-            }
-
-            _borrowerMemory = dstProcess.CpuMemory;
-            _borrowerVa = va;
-        }
-
         public void ZeroFill()
         {
             for (ulong offset = 0; offset < _size; offset += sizeof(ulong))
@@ -57,42 +32,13 @@ namespace Ryujinx.HLE.HOS.Kernel.Memory
 
         public ref T GetRef<T>(ulong offset) where T : unmanaged
         {
-            if (_borrowerMemory == null)
+            if (_pageList.Nodes.Count == 1)
             {
-                if (_pageList.Nodes.Count == 1)
-                {
-                    ulong address = _pageList.Nodes.First.Value.Address - DramMemoryMap.DramBase;
-                    return ref _context.Memory.GetRef<T>(address + offset);
-                }
-
-                throw new NotImplementedException("Non-contiguous shared memory is not yet supported.");
+                ulong address = _pageList.Nodes.First.Value.Address - DramMemoryMap.DramBase;
+                return ref _context.Memory.GetRef<T>(address + offset);
             }
-            else
-            {
-                return ref _borrowerMemory.GetRef<T>(_borrowerVa + offset);
-            }
-        }
 
-        public IEnumerable<HostMemoryRange> GetRanges()
-        {
-            if (_borrowerMemory == null)
-            {
-                var ranges = new List<HostMemoryRange>();
-
-                foreach (KPageNode pageNode in _pageList)
-                {
-                    ulong address = pageNode.Address - DramMemoryMap.DramBase;
-                    ulong size = pageNode.PagesCount * KPageTableBase.PageSize;
-
-                    ranges.Add(new HostMemoryRange(_context.Memory.GetPointer(address, size), size));
-                }
-
-                return ranges;
-            }
-            else
-            {
-                return _borrowerMemory.GetPhysicalRegions(_borrowerVa, _size);
-            }
+            throw new NotImplementedException("Non-contiguous shared memory is not yet supported.");
         }
 
         public KPageList GetPageList()

Ryujinx.HLE/HOS/Kernel/Process/KProcess.cs

@@ -1076,14 +1076,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Process
 
             Context = _contextFactory.Create(KernelContext, Pid, 1UL << addrSpaceBits, InvalidAccessHandler, for64Bit);
 
-            if (Context.AddressSpace is MemoryManagerHostMapped)
-            {
-                MemoryManager = new KPageTableHostMapped(KernelContext, CpuMemory);
-            }
-            else
-            {
-                MemoryManager = new KPageTable(KernelContext, CpuMemory);
-            }
+            MemoryManager = new KPageTable(KernelContext, CpuMemory);
         }
 
         private bool InvalidAccessHandler(ulong va)

Ryujinx.HLE/HOS/Kernel/Process/ProcessContextFactory.cs

@@ -6,7 +6,7 @@ namespace Ryujinx.HLE.HOS.Kernel.Process
     {
         public IProcessContext Create(KernelContext context, ulong pid, ulong addressSpaceSize, InvalidAccessHandler invalidAccessHandler, bool for64Bit)
         {
-            return new ProcessContext(new AddressSpaceManager(addressSpaceSize));
+            return new ProcessContext(new AddressSpaceManager(context.Memory, addressSpaceSize));
         }
     }
 }

Ryujinx.HLE/HOS/Services/Ro/IRoInterface.cs

@@ -5,6 +5,7 @@ using Ryujinx.HLE.HOS.Kernel.Common;
 using Ryujinx.HLE.HOS.Kernel.Memory;
 using Ryujinx.HLE.HOS.Kernel.Process;
 using Ryujinx.HLE.Loaders.Executables;
+using Ryujinx.Memory;
 using System;
 using System.Collections.Generic;
 using System.IO;
@@ -566,6 +567,11 @@ namespace Ryujinx.HLE.HOS.Services.Ro
             _owner = context.Process.HandleTable.GetKProcess(context.Request.HandleDesc.ToCopy[0]);
             context.Device.System.KernelContext.Syscall.CloseHandle(context.Request.HandleDesc.ToCopy[0]);
 
+            if (_owner?.CpuMemory is IRefCounted rc)
+            {
+                rc.IncrementReferenceCount();
+            }
+
             return ResultCode.Success;
         }
 
@@ -579,6 +585,11 @@ namespace Ryujinx.HLE.HOS.Services.Ro
                 }
 
                 _nroInfos.Clear();
+
+                if (_owner?.CpuMemory is IRefCounted rc)
+                {
+                    rc.DecrementReferenceCount();
+                }
             }
         }
     }

Ryujinx.HLE/Switch.cs

@@ -1,5 +1,6 @@
 using Ryujinx.Audio.Backends.CompatLayer;
 using Ryujinx.Audio.Integration;
+using Ryujinx.Common.Configuration;
 using Ryujinx.Graphics.Gpu;
 using Ryujinx.HLE.FileSystem;
 using Ryujinx.HLE.HOS;
@@ -48,8 +49,12 @@ namespace Ryujinx.HLE
             FileSystem    = Configuration.VirtualFileSystem;
             UiHandler     = Configuration.HostUiHandler;
 
+            MemoryAllocationFlags memoryAllocationFlags = configuration.MemoryManagerMode == MemoryManagerMode.SoftwarePageTable
+                ? MemoryAllocationFlags.Reserve
+                : MemoryAllocationFlags.Reserve | MemoryAllocationFlags.Mirrorable;
+
             AudioDeviceDriver = new CompatLayerHardwareDeviceDriver(Configuration.AudioDeviceDriver);
-            Memory            = new MemoryBlock(Configuration.MemoryConfiguration.ToDramSize(), MemoryAllocationFlags.Reserve);
+            Memory            = new MemoryBlock(Configuration.MemoryConfiguration.ToDramSize(), memoryAllocationFlags);
             Gpu               = new GpuContext(Configuration.GpuRenderer);
             System            = new Horizon(this);
             Statistics        = new PerformanceStatistics();

Ryujinx.Memory.Tests/MockVirtualMemoryManager.cs

@@ -14,7 +14,7 @@ namespace Ryujinx.Memory.Tests
         {
         }
 
-        public void Map(ulong va, nuint hostAddress, ulong size)
+        public void Map(ulong va, ulong pa, ulong size)
         {
             throw new NotImplementedException();
         }
@@ -59,9 +59,9 @@ namespace Ryujinx.Memory.Tests
             throw new NotImplementedException();
         }
 
-        IEnumerable<HostMemoryRange> IVirtualMemoryManager.GetPhysicalRegions(ulong va, ulong size)
+        IEnumerable<MemoryRange> IVirtualMemoryManager.GetPhysicalRegions(ulong va, ulong size)
         {
-            return NoMappings ? new HostMemoryRange[0] : new HostMemoryRange[] { new HostMemoryRange((nuint)va, size) };
+            return NoMappings ? new MemoryRange[0] : new MemoryRange[] { new MemoryRange(va, size) };
         }
 
         public bool IsMapped(ulong va)

Ryujinx.Memory.Tests/Tests.cs

@@ -1,5 +1,4 @@
 using NUnit.Framework;
-using Ryujinx.Memory;
 using System;
 using System.Runtime.InteropServices;
 
@@ -38,5 +37,48 @@ namespace Ryujinx.Memory.Tests
 
             Assert.AreEqual(Marshal.ReadInt32(_memoryBlock.Pointer, 0x2040), 0xbadc0de);
         }
+
+        [Test, Explicit]
+        public void Test_Alias()
+        {
+            using MemoryBlock backing = new MemoryBlock(0x10000, MemoryAllocationFlags.Mirrorable);
+            using MemoryBlock toAlias = new MemoryBlock(0x10000, MemoryAllocationFlags.Reserve | MemoryAllocationFlags.ViewCompatible);
+
+            toAlias.MapView(backing, 0x1000, 0, 0x4000);
+            toAlias.UnmapView(backing, 0x3000, 0x1000);
+
+            toAlias.Write(0, 0xbadc0de);
+            Assert.AreEqual(Marshal.ReadInt32(backing.Pointer, 0x1000), 0xbadc0de);
+        }
+
+        [Test, Explicit]
+        public void Test_AliasRandom()
+        {
+            using MemoryBlock backing = new MemoryBlock(0x80000, MemoryAllocationFlags.Mirrorable);
+            using MemoryBlock toAlias = new MemoryBlock(0x80000, MemoryAllocationFlags.Reserve | MemoryAllocationFlags.ViewCompatible);
+
+            Random rng = new Random(123);
+
+            for (int i = 0; i < 20000; i++)
+            {
+                int srcPage = rng.Next(0, 64);
+                int dstPage = rng.Next(0, 64);
+                int pages = rng.Next(1, 65);
+
+                if ((rng.Next() & 1) != 0)
+                {
+                    toAlias.MapView(backing, (ulong)srcPage << 12, (ulong)dstPage << 12, (ulong)pages << 12);
+
+                    int offset = rng.Next(0, 0x1000 - sizeof(int));
+
+                    toAlias.Write((ulong)((dstPage << 12) + offset), 0xbadc0de);
+                    Assert.AreEqual(Marshal.ReadInt32(backing.Pointer, (srcPage << 12) + offset), 0xbadc0de);
+                }
+                else
+                {
+                    toAlias.UnmapView(backing, (ulong)dstPage << 12, (ulong)pages << 12);
+                }
+            }
+        }
     }
 }

Ryujinx.Memory/AddressSpaceManager.cs

@@ -13,9 +13,9 @@ namespace Ryujinx.Memory
     /// </summary>
     public sealed class AddressSpaceManager : IVirtualMemoryManager, IWritableBlock
     {
-        public const int PageBits = PageTable<nuint>.PageBits;
-        public const int PageSize = PageTable<nuint>.PageSize;
-        public const int PageMask = PageTable<nuint>.PageMask;
+        public const int PageBits = PageTable<ulong>.PageBits;
+        public const int PageSize = PageTable<ulong>.PageSize;
+        public const int PageMask = PageTable<ulong>.PageMask;
 
         /// <summary>
         /// Address space width in bits.
@@ -24,14 +24,15 @@ namespace Ryujinx.Memory
 
         private readonly ulong _addressSpaceSize;
 
-        private readonly PageTable<nuint> _pageTable;
+        private readonly MemoryBlock _backingMemory;
+        private readonly PageTable<ulong> _pageTable;
 
         /// <summary>
         /// Creates a new instance of the memory manager.
         /// </summary>
         /// <param name="backingMemory">Physical backing memory where virtual memory will be mapped to</param>
         /// <param name="addressSpaceSize">Size of the address space</param>
-        public AddressSpaceManager(ulong addressSpaceSize)
+        public AddressSpaceManager(MemoryBlock backingMemory, ulong addressSpaceSize)
         {
             ulong asSize = PageSize;
             int asBits = PageBits;
@@ -44,37 +45,26 @@ namespace Ryujinx.Memory
 
             AddressSpaceBits = asBits;
             _addressSpaceSize = asSize;
-            _pageTable = new PageTable<nuint>();
+            _backingMemory = backingMemory;
+            _pageTable = new PageTable<ulong>();
         }
 
-        /// <summary>
-        /// Maps a virtual memory range into a physical memory range.
-        /// </summary>
-        /// <remarks>
-        /// Addresses and size must be page aligned.
-        /// </remarks>
-        /// <param name="va">Virtual memory address</param>
-        /// <param name="hostAddress">Physical memory address</param>
-        /// <param name="size">Size to be mapped</param>
-        public void Map(ulong va, nuint hostAddress, ulong size)
+        /// <inheritdoc/>
+        public void Map(ulong va, ulong pa, ulong size)
         {
             AssertValidAddressAndSize(va, size);
 
             while (size != 0)
             {
-                _pageTable.Map(va, hostAddress);
+                _pageTable.Map(va, pa);
 
                 va += PageSize;
-                hostAddress += PageSize;
+                pa += PageSize;
                 size -= PageSize;
             }
         }
 
-        /// <summary>
-        /// Unmaps a previously mapped range of virtual memory.
-        /// </summary>
-        /// <param name="va">Virtual address of the range to be unmapped</param>
-        /// <param name="size">Size of the range to be unmapped</param>
+        /// <inheritdoc/>
         public void Unmap(ulong va, ulong size)
         {
             AssertValidAddressAndSize(va, size);
@@ -88,47 +78,25 @@ namespace Ryujinx.Memory
             }
         }
 
-        /// <summary>
-        /// Reads data from mapped memory.
-        /// </summary>
-        /// <typeparam name="T">Type of the data being read</typeparam>
-        /// <param name="va">Virtual address of the data in memory</param>
-        /// <returns>The data</returns>
-        /// <exception cref="InvalidMemoryRegionException">Throw for unhandled invalid or unmapped memory accesses</exception>
+        /// <inheritdoc/>
         public T Read<T>(ulong va) where T : unmanaged
         {
             return MemoryMarshal.Cast<byte, T>(GetSpan(va, Unsafe.SizeOf<T>()))[0];
         }
 
-        /// <summary>
-        /// Reads data from mapped memory.
-        /// </summary>
-        /// <param name="va">Virtual address of the data in memory</param>
-        /// <param name="data">Span to store the data being read into</param>
-        /// <exception cref="InvalidMemoryRegionException">Throw for unhandled invalid or unmapped memory accesses</exception>
+        /// <inheritdoc/>
         public void Read(ulong va, Span<byte> data)
         {
             ReadImpl(va, data);
         }
 
-        /// <summary>
-        /// Writes data to mapped memory.
-        /// </summary>
-        /// <typeparam name="T">Type of the data being written</typeparam>
-        /// <param name="va">Virtual address to write the data into</param>
-        /// <param name="value">Data to be written</param>
-        /// <exception cref="InvalidMemoryRegionException">Throw for unhandled invalid or unmapped memory accesses</exception>
+        /// <inheritdoc/>
         public void Write<T>(ulong va, T value) where T : unmanaged
         {
             Write(va, MemoryMarshal.Cast<T, byte>(MemoryMarshal.CreateSpan(ref value, 1)));
         }
 
-        /// <summary>
-        /// Writes data to mapped memory.
-        /// </summary>
-        /// <param name="va">Virtual address to write the data into</param>
-        /// <param name="data">Data to be written</param>
-        /// <exception cref="InvalidMemoryRegionException">Throw for unhandled invalid or unmapped memory accesses</exception>
+        /// <inheritdoc/>
         public void Write(ulong va, ReadOnlySpan<byte> data)
         {
             if (data.Length == 0)
@@ -140,7 +108,7 @@ namespace Ryujinx.Memory
 
             if (IsContiguousAndMapped(va, data.Length))
             {
-                data.CopyTo(GetHostSpanContiguous(va, data.Length));
+                data.CopyTo(_backingMemory.GetSpan(GetPhysicalAddressInternal(va), data.Length));
             }
             else
             {
@@ -148,34 +116,27 @@ namespace Ryujinx.Memory
 
                 if ((va & PageMask) != 0)
                 {
+                    ulong pa = GetPhysicalAddressInternal(va);
+
                     size = Math.Min(data.Length, PageSize - (int)(va & PageMask));
 
-                    data.Slice(0, size).CopyTo(GetHostSpanContiguous(va, size));
+                    data.Slice(0, size).CopyTo(_backingMemory.GetSpan(pa, size));
 
                     offset += size;
                 }
 
                 for (; offset < data.Length; offset += size)
                 {
+                    ulong pa = GetPhysicalAddressInternal(va + (ulong)offset);
+
                     size = Math.Min(data.Length - offset, PageSize);
 
-                    data.Slice(offset, size).CopyTo(GetHostSpanContiguous(va + (ulong)offset, size));
+                    data.Slice(offset, size).CopyTo(_backingMemory.GetSpan(pa, size));
                 }
             }
         }
 
-        /// <summary>
-        /// Gets a read-only span of data from mapped memory.
-        /// </summary>
-        /// <remarks>
-        /// This may perform a allocation if the data is not contiguous in memory.
-        /// For this reason, the span is read-only, you can't modify the data.
-        /// </remarks>
-        /// <param name="va">Virtual address of the data</param>
-        /// <param name="size">Size of the data</param>
-        /// <param name="tracked">True if read tracking is triggered on the span</param>
-        /// <returns>A read-only span of the data</returns>
-        /// <exception cref="InvalidMemoryRegionException">Throw for unhandled invalid or unmapped memory accesses</exception>
+        /// <inheritdoc/>
         public ReadOnlySpan<byte> GetSpan(ulong va, int size, bool tracked = false)
         {
             if (size == 0)
@@ -185,7 +146,7 @@ namespace Ryujinx.Memory
 
             if (IsContiguousAndMapped(va, size))
             {
-                return GetHostSpanContiguous(va, size);
+                return _backingMemory.GetSpan(GetPhysicalAddressInternal(va), size);
             }
             else
             {
@@ -197,19 +158,7 @@ namespace Ryujinx.Memory
             }
         }
 
-        /// <summary>
-        /// Gets a region of memory that can be written to.
-        /// </summary>
-        /// <remarks>
-        /// If the requested region is not contiguous in physical memory,
-        /// this will perform an allocation, and flush the data (writing it
-        /// back to the backing memory) on disposal.
-        /// </remarks>
-        /// <param name="va">Virtual address of the data</param>
-        /// <param name="size">Size of the data</param>
-        /// <param name="tracked">True if write tracking is triggered on the span</param>
-        /// <returns>A writable region of memory containing the data</returns>
-        /// <exception cref="InvalidMemoryRegionException">Throw for unhandled invalid or unmapped memory accesses</exception>
+        /// <inheritdoc/>
         public unsafe WritableRegion GetWritableRegion(ulong va, int size, bool tracked = false)
         {
             if (size == 0)
@@ -219,7 +168,7 @@ namespace Ryujinx.Memory
 
             if (IsContiguousAndMapped(va, size))
             {
-                return new WritableRegion(null, va, new NativeMemoryManager<byte>((byte*)GetHostAddress(va), size).Memory);
+                return new WritableRegion(null, va, _backingMemory.GetMemory(GetPhysicalAddressInternal(va), size));
             }
             else
             {
@@ -231,33 +180,18 @@ namespace Ryujinx.Memory
             }
         }
 
-        /// <summary>
-        /// Gets a reference for the given type at the specified virtual memory address.
-        /// </summary>
-        /// <remarks>
-        /// The data must be located at a contiguous memory region.
-        /// </remarks>
-        /// <typeparam name="T">Type of the data to get the reference</typeparam>
-        /// <param name="va">Virtual address of the data</param>
-        /// <returns>A reference to the data in memory</returns>
-        /// <exception cref="MemoryNotContiguousException">Throw if the specified memory region is not contiguous in physical memory</exception>
-        public unsafe ref T GetRef<T>(ulong va) where T : unmanaged
+        /// <inheritdoc/>
+        public ref T GetRef<T>(ulong va) where T : unmanaged
         {
             if (!IsContiguous(va, Unsafe.SizeOf<T>()))
             {
                 ThrowMemoryNotContiguous();
             }
 
-            return ref *(T*)GetHostAddress(va);
+            return ref _backingMemory.GetRef<T>(GetPhysicalAddressInternal(va));
         }
 
-        /// <summary>
-        /// Computes the number of pages in a virtual address range.
-        /// </summary>
-        /// <param name="va">Virtual address of the range</param>
-        /// <param name="size">Size of the range</param>
-        /// <param name="startVa">The virtual address of the beginning of the first page</param>
-        /// <remarks>This function does not differentiate between allocated and unallocated pages.</remarks>
+        /// <inheritdoc/>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private int GetPagesCount(ulong va, uint size, out ulong startVa)
         {
@@ -268,7 +202,7 @@ namespace Ryujinx.Memory
             return (int)(vaSpan / PageSize);
         }
 
-        private void ThrowMemoryNotContiguous() => throw new MemoryNotContiguousException();
+        private static void ThrowMemoryNotContiguous() => throw new MemoryNotContiguousException();
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private bool IsContiguousAndMapped(ulong va, int size) => IsContiguous(va, size) && IsMapped(va);
@@ -290,7 +224,7 @@ namespace Ryujinx.Memory
                     return false;
                 }
 
-                if (GetHostAddress(va) + PageSize != GetHostAddress(va + PageSize))
+                if (GetPhysicalAddressInternal(va) + PageSize != GetPhysicalAddressInternal(va + PageSize))
                 {
                     return false;
                 }
@@ -301,18 +235,12 @@ namespace Ryujinx.Memory
             return true;
         }
 
-        /// <summary>
-        /// Gets the physical regions that make up the given virtual address region.
-        /// If any part of the virtual region is unmapped, null is returned.
-        /// </summary>
-        /// <param name="va">Virtual address of the range</param>
-        /// <param name="size">Size of the range</param>
-        /// <returns>Array of physical regions</returns>
-        public IEnumerable<HostMemoryRange> GetPhysicalRegions(ulong va, ulong size)
+        /// <inheritdoc/>
+        public IEnumerable<MemoryRange> GetPhysicalRegions(ulong va, ulong size)
         {
             if (size == 0)
             {
-                return Enumerable.Empty<HostMemoryRange>();
+                return Enumerable.Empty<MemoryRange>();
             }
 
             if (!ValidateAddress(va) || !ValidateAddressAndSize(va, size))
@@ -322,9 +250,9 @@ namespace Ryujinx.Memory
 
             int pages = GetPagesCount(va, (uint)size, out va);
 
-            var regions = new List<HostMemoryRange>();
+            var regions = new List<MemoryRange>();
 
-            nuint regionStart = GetHostAddress(va);
+            ulong regionStart = GetPhysicalAddressInternal(va);
             ulong regionSize = PageSize;
 
             for (int page = 0; page < pages - 1; page++)
@@ -334,12 +262,12 @@ namespace Ryujinx.Memory
                     return null;
                 }
 
-                nuint newHostAddress = GetHostAddress(va + PageSize);
+                ulong newPa = GetPhysicalAddressInternal(va + PageSize);
 
-                if (GetHostAddress(va) + PageSize != newHostAddress)
+                if (GetPhysicalAddressInternal(va) + PageSize != newPa)
                 {
-                    regions.Add(new HostMemoryRange(regionStart, regionSize));
-                    regionStart = newHostAddress;
+                    regions.Add(new MemoryRange(regionStart, regionSize));
+                    regionStart = newPa;
                     regionSize = 0;
                 }
 
@@ -347,7 +275,7 @@ namespace Ryujinx.Memory
                 regionSize += PageSize;
             }
 
-            regions.Add(new HostMemoryRange(regionStart, regionSize));
+            regions.Add(new MemoryRange(regionStart, regionSize));
 
             return regions;
         }
@@ -365,26 +293,26 @@ namespace Ryujinx.Memory
 
             if ((va & PageMask) != 0)
             {
+                ulong pa = GetPhysicalAddressInternal(va);
+
                 size = Math.Min(data.Length, PageSize - (int)(va & PageMask));
 
-                GetHostSpanContiguous(va, size).CopyTo(data.Slice(0, size));
+                _backingMemory.GetSpan(pa, size).CopyTo(data.Slice(0, size));
 
                 offset += size;
             }
 
             for (; offset < data.Length; offset += size)
             {
+                ulong pa = GetPhysicalAddressInternal(va + (ulong)offset);
+
                 size = Math.Min(data.Length - offset, PageSize);
 
-                GetHostSpanContiguous(va + (ulong)offset, size).CopyTo(data.Slice(offset, size));
+                _backingMemory.GetSpan(pa, size).CopyTo(data.Slice(offset, size));
             }
         }
 
-        /// <summary>
-        /// Checks if the page at a given virtual address is mapped.
-        /// </summary>
-        /// <param name="va">Virtual address to check</param>
-        /// <returns>True if the address is mapped, false otherwise</returns>
+        /// <inheritdoc/>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public bool IsMapped(ulong va)
         {
@@ -396,12 +324,7 @@ namespace Ryujinx.Memory
             return _pageTable.Read(va) != 0;
         }
 
-        /// <summary>
-        /// Checks if a memory range is mapped.
-        /// </summary>
-        /// <param name="va">Virtual address of the range</param>
-        /// <param name="size">Size of the range in bytes</param>
-        /// <returns>True if the entire range is mapped, false otherwise</returns>
+        /// <inheritdoc/>
         public bool IsRangeMapped(ulong va, ulong size)
         {
             if (size == 0UL)
@@ -460,14 +383,9 @@ namespace Ryujinx.Memory
             }
         }
 
-        private unsafe Span<byte> GetHostSpanContiguous(ulong va, int size)
+        private ulong GetPhysicalAddressInternal(ulong va)
         {
-            return new Span<byte>((void*)GetHostAddress(va), size);
-        }
-
-        private nuint GetHostAddress(ulong va)
-        {
-            return _pageTable.Read(va) + (nuint)(va & PageMask);
+            return _pageTable.Read(va) + (va & PageMask);
         }
 
         /// <summary>

Ryujinx.Memory/IVirtualMemoryManager.cs

@@ -13,9 +13,9 @@ namespace Ryujinx.Memory
         /// Addresses and size must be page aligned.
         /// </remarks>
         /// <param name="va">Virtual memory address</param>
-        /// <param name="hostAddress">Pointer where the region should be mapped to</param>
+        /// <param name="pa">Physical memory address where the region should be mapped to</param>
         /// <param name="size">Size to be mapped</param>
-        void Map(ulong va, nuint hostAddress, ulong size);
+        void Map(ulong va, ulong pa, ulong size);
 
         /// <summary>
         /// Unmaps a previously mapped range of virtual memory.
@@ -111,7 +111,7 @@ namespace Ryujinx.Memory
         /// <param name="va">Virtual address of the range</param>
         /// <param name="size">Size of the range</param>
         /// <returns>Array of physical regions</returns>
-        IEnumerable<HostMemoryRange> GetPhysicalRegions(ulong va, ulong size);
+        IEnumerable<MemoryRange> GetPhysicalRegions(ulong va, ulong size);
 
         /// <summary>
         /// Checks if the page at a given CPU virtual address is mapped.

Ryujinx.Memory/MemoryAllocationFlags.cs

@@ -29,6 +29,18 @@ namespace Ryujinx.Memory
         /// Enables mirroring of the memory block through aliasing of memory pages.
         /// When enabled, this allows creating more memory blocks sharing the same backing storage.
         /// </summary>
-        Mirrorable = 1 << 2
+        Mirrorable = 1 << 2,
+
+        /// <summary>
+        /// Indicates that the memory block should support mapping views of a mirrorable memory block.
+        /// The block that is to have their views mapped should be created with the <see cref="Mirrorable"/> flag.
+        /// </summary>
+        ViewCompatible = 1 << 3,
+
+        /// <summary>
+        /// Forces views to be mapped page by page on Windows. When partial unmaps are done, this avoids the need
+        /// to unmap the full range and remap sub-ranges, which creates a time window with incorrectly unmapped memory.
+        /// </summary>
+        ForceWindows4KBViewMapping = 1 << 4
     }
 }

Ryujinx.Memory/MemoryBlock.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Concurrent;
 using System.Runtime.CompilerServices;
 using System.Threading;
 
@@ -11,8 +12,12 @@ namespace Ryujinx.Memory
     {
         private readonly bool _usesSharedMemory;
         private readonly bool _isMirror;
+        private readonly bool _viewCompatible;
+        private readonly bool _forceWindows4KBView;
         private IntPtr _sharedMemory;
         private IntPtr _pointer;
+        private ConcurrentDictionary<MemoryBlock, byte> _viewStorages;
+        private int _viewCount;
 
         /// <summary>
         /// Pointer to the memory block data.
@@ -36,12 +41,14 @@ namespace Ryujinx.Memory
             if (flags.HasFlag(MemoryAllocationFlags.Mirrorable))
             {
                 _sharedMemory = MemoryManagement.CreateSharedMemory(size, flags.HasFlag(MemoryAllocationFlags.Reserve));
-                _pointer = MemoryManagement.MapSharedMemory(_sharedMemory);
+                _pointer = MemoryManagement.MapSharedMemory(_sharedMemory, size);
                 _usesSharedMemory = true;
             }
             else if (flags.HasFlag(MemoryAllocationFlags.Reserve))
             {
-                _pointer = MemoryManagement.Reserve(size);
+                _viewCompatible = flags.HasFlag(MemoryAllocationFlags.ViewCompatible);
+                _forceWindows4KBView = flags.HasFlag(MemoryAllocationFlags.ForceWindows4KBViewMapping);
+                _pointer = MemoryManagement.Reserve(size, _viewCompatible);
             }
             else
             {
@@ -49,6 +56,10 @@ namespace Ryujinx.Memory
             }
 
             Size = size;
+
+            _viewStorages = new ConcurrentDictionary<MemoryBlock, byte>();
+            _viewStorages.TryAdd(this, 0);
+            _viewCount = 1;
         }
 
         /// <summary>
@@ -60,7 +71,7 @@ namespace Ryujinx.Memory
         /// <exception cref="PlatformNotSupportedException">Throw when the current platform is not supported</exception>
         private MemoryBlock(ulong size, IntPtr sharedMemory)
         {
-            _pointer = MemoryManagement.MapSharedMemory(sharedMemory);
+            _pointer = MemoryManagement.MapSharedMemory(sharedMemory, size);
             Size = size;
             _usesSharedMemory = true;
             _isMirror = true;
@@ -112,6 +123,42 @@ namespace Ryujinx.Memory
             return MemoryManagement.Decommit(GetPointerInternal(offset, size), size);
         }
 
+        /// <summary>
+        /// Maps a view of memory from another memory block.
+        /// </summary>
+        /// <param name="srcBlock">Memory block from where the backing memory will be taken</param>
+        /// <param name="srcOffset">Offset on <paramref name="srcBlock"/> of the region that should be mapped</param>
+        /// <param name="dstOffset">Offset to map the view into on this block</param>
+        /// <param name="size">Size of the range to be mapped</param>
+        /// <exception cref="NotSupportedException">Throw when the source memory block does not support mirroring</exception>
+        /// <exception cref="ObjectDisposedException">Throw when the memory block has already been disposed</exception>
+        /// <exception cref="InvalidMemoryRegionException">Throw when either <paramref name="offset"/> or <paramref name="size"/> are out of range</exception>
+        public void MapView(MemoryBlock srcBlock, ulong srcOffset, ulong dstOffset, ulong size)
+        {
+            if (srcBlock._sharedMemory == IntPtr.Zero)
+            {
+                throw new ArgumentException("The source memory block is not mirrorable, and thus cannot be mapped on the current block.");
+            }
+
+            if (_viewStorages.TryAdd(srcBlock, 0))
+            {
+                srcBlock.IncrementViewCount();
+            }
+
+            MemoryManagement.MapView(srcBlock._sharedMemory, srcOffset, GetPointerInternal(dstOffset, size), size, _forceWindows4KBView);
+        }
+
+        /// <summary>
+        /// Unmaps a view of memory from another memory block.
+        /// </summary>
+        /// <param name="srcBlock">Memory block from where the backing memory was taken during map</param>
+        /// <param name="offset">Offset of the view previously mapped with <see cref="MapView"/></param>
+        /// <param name="size">Size of the range to be unmapped</param>
+        public void UnmapView(MemoryBlock srcBlock, ulong offset, ulong size)
+        {
+            MemoryManagement.UnmapView(srcBlock._sharedMemory, GetPointerInternal(offset, size), size, _forceWindows4KBView);
+        }
+
         /// <summary>
         /// Reprotects a region of memory.
         /// </summary>
@@ -124,21 +171,7 @@ namespace Ryujinx.Memory
         /// <exception cref="MemoryProtectionException">Throw when <paramref name="permission"/> is invalid</exception>
         public void Reprotect(ulong offset, ulong size, MemoryPermission permission, bool throwOnFail = true)
         {
-            MemoryManagement.Reprotect(GetPointerInternal(offset, size), size, permission, throwOnFail);
-        }
-
-        /// <summary>
-        /// Remaps a region of memory into this memory block.
-        /// </summary>
-        /// <param name="offset">Starting offset of the range to be remapped into</param>
-        /// <param name="sourceAddress">Starting offset of the range to be remapped from</param>
-        /// <param name="size">Size of the range to be remapped</param>
-        /// <exception cref="ObjectDisposedException">Throw when the memory block has already been disposed</exception>
-        /// <exception cref="InvalidMemoryRegionException">Throw when either <paramref name="offset"/> or <paramref name="size"/> are out of range</exception>
-        /// <exception cref="MemoryProtectionException">Throw when <paramref name="permission"/> is invalid</exception>
-        public void Remap(ulong offset, IntPtr sourceAddress, ulong size)
-        {
-            MemoryManagement.Remap(GetPointerInternal(offset, size), sourceAddress, size);
+            MemoryManagement.Reprotect(GetPointerInternal(offset, size), size, permission, _viewCompatible, _forceWindows4KBView, throwOnFail);
         }
 
         /// <summary>
@@ -274,7 +307,7 @@ namespace Ryujinx.Memory
         /// <exception cref="ObjectDisposedException">Throw when the memory block has already been disposed</exception>
         /// <exception cref="InvalidMemoryRegionException">Throw when either <paramref name="offset"/> or <paramref name="size"/> are out of range</exception>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public nuint GetPointer(ulong offset, ulong size) => (nuint)(ulong)GetPointerInternal(offset, size);
+        public IntPtr GetPointer(ulong offset, ulong size) => GetPointerInternal(offset, size);
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         private IntPtr GetPointerInternal(ulong offset, ulong size)
@@ -367,22 +400,63 @@ namespace Ryujinx.Memory
             {
                 if (_usesSharedMemory)
                 {
-                    MemoryManagement.UnmapSharedMemory(ptr);
-
-                    if (_sharedMemory != IntPtr.Zero && !_isMirror)
-                    {
-                        MemoryManagement.DestroySharedMemory(_sharedMemory);
-                        _sharedMemory = IntPtr.Zero;
-                    }
+                    MemoryManagement.UnmapSharedMemory(ptr, Size);
                 }
                 else
                 {
                     MemoryManagement.Free(ptr);
                 }
+
+                foreach (MemoryBlock viewStorage in _viewStorages.Keys)
+                {
+                    viewStorage.DecrementViewCount();
+                }
+
+                _viewStorages.Clear();
             }
         }
 
-        private void ThrowObjectDisposed() => throw new ObjectDisposedException(nameof(MemoryBlock));
-        private void ThrowInvalidMemoryRegionException() => throw new InvalidMemoryRegionException();
+        /// <summary>
+        /// Increments the number of views that uses this memory block as storage.
+        /// </summary>
+        private void IncrementViewCount()
+        {
+            Interlocked.Increment(ref _viewCount);
+        }
+
+        /// <summary>
+        /// Decrements the number of views that uses this memory block as storage.
+        /// </summary>
+        private void DecrementViewCount()
+        {
+            if (Interlocked.Decrement(ref _viewCount) == 0 && _sharedMemory != IntPtr.Zero && !_isMirror)
+            {
+                MemoryManagement.DestroySharedMemory(_sharedMemory);
+                _sharedMemory = IntPtr.Zero;
+            }
+        }
+
+        /// <summary>
+        /// Checks if the specified memory allocation flags are supported on the current platform.
+        /// </summary>
+        /// <param name="flags">Flags to be checked</param>
+        /// <returns>True if the platform supports all the flags, false otherwise</returns>
+        public static bool SupportsFlags(MemoryAllocationFlags flags)
+        {
+            if (flags.HasFlag(MemoryAllocationFlags.ViewCompatible))
+            {
+                if (OperatingSystem.IsWindows())
+                {
+                    return OperatingSystem.IsWindowsVersionAtLeast(10, 0, 17134);
+                }
+
+                return OperatingSystem.IsLinux() || OperatingSystem.IsMacOS();
+            }
+
+            return true;
+        }
+
+        private static void ThrowObjectDisposed() => throw new ObjectDisposedException(nameof(MemoryBlock));
+        private static void ThrowInvalidMemoryRegionException() => throw new InvalidMemoryRegionException();
     }
 }

Ryujinx.Memory/MemoryManagement.cs

@@ -12,8 +12,7 @@ namespace Ryujinx.Memory
 
                 return MemoryManagementWindows.Allocate(sizeNint);
             }
-            else if (OperatingSystem.IsLinux() ||
-                     OperatingSystem.IsMacOS())
+            else if (OperatingSystem.IsLinux() || OperatingSystem.IsMacOS())
             {
                 return MemoryManagementUnix.Allocate(size);
             }
@@ -23,16 +22,15 @@ namespace Ryujinx.Memory
             }
         }
 
-        public static IntPtr Reserve(ulong size)
+        public static IntPtr Reserve(ulong size, bool viewCompatible)
         {
             if (OperatingSystem.IsWindows())
             {
                 IntPtr sizeNint = new IntPtr((long)size);
 
-                return MemoryManagementWindows.Reserve(sizeNint);
+                return MemoryManagementWindows.Reserve(sizeNint, viewCompatible);
             }
-            else if (OperatingSystem.IsLinux() ||
-                     OperatingSystem.IsMacOS())
+            else if (OperatingSystem.IsLinux() || OperatingSystem.IsMacOS())
             {
                 return MemoryManagementUnix.Reserve(size);
             }
@@ -50,8 +48,7 @@ namespace Ryujinx.Memory
 
                 return MemoryManagementWindows.Commit(address, sizeNint);
             }
-            else if (OperatingSystem.IsLinux() ||
-                     OperatingSystem.IsMacOS())
+            else if (OperatingSystem.IsLinux() || OperatingSystem.IsMacOS())
             {
                 return MemoryManagementUnix.Commit(address, size);
             }
@@ -69,8 +66,7 @@ namespace Ryujinx.Memory
 
                 return MemoryManagementWindows.Decommit(address, sizeNint);
             }
-            else if (OperatingSystem.IsLinux() ||
-                     OperatingSystem.IsMacOS())
+            else if (OperatingSystem.IsLinux() || OperatingSystem.IsMacOS())
             {
                 return MemoryManagementUnix.Decommit(address, size);
             }
@@ -80,7 +76,57 @@ namespace Ryujinx.Memory
             }
         }
 
-        public static void Reprotect(IntPtr address, ulong size, MemoryPermission permission, bool throwOnFail)
+        public static void MapView(IntPtr sharedMemory, ulong srcOffset, IntPtr address, ulong size, bool force4KBMap)
+        {
+            if (OperatingSystem.IsWindows())
+            {
+                IntPtr sizeNint = new IntPtr((long)size);
+
+                if (force4KBMap)
+                {
+                    MemoryManagementWindows.MapView4KB(sharedMemory, srcOffset, address, sizeNint);
+                }
+                else
+                {
+                    MemoryManagementWindows.MapView(sharedMemory, srcOffset, address, sizeNint);
+                }
+            }
+            else if (OperatingSystem.IsLinux() || OperatingSystem.IsMacOS())
+            {
+                MemoryManagementUnix.MapView(sharedMemory, srcOffset, address, size);
+            }
+            else
+            {
+                throw new PlatformNotSupportedException();
+            }
+        }
+
+        public static void UnmapView(IntPtr sharedMemory, IntPtr address, ulong size, bool force4KBMap)
+        {
+            if (OperatingSystem.IsWindows())
+            {
+                IntPtr sizeNint = new IntPtr((long)size);
+
+                if (force4KBMap)
+                {
+                    MemoryManagementWindows.UnmapView4KB(address, sizeNint);
+                }
+                else
+                {
+                    MemoryManagementWindows.UnmapView(sharedMemory, address, sizeNint);
+                }
+            }
+            else if (OperatingSystem.IsLinux() || OperatingSystem.IsMacOS())
+            {
+                MemoryManagementUnix.UnmapView(address, size);
+            }
+            else
+            {
+                throw new PlatformNotSupportedException();
+            }
+        }
+
+        public static void Reprotect(IntPtr address, ulong size, MemoryPermission permission, bool forView, bool force4KBMap, bool throwOnFail)
         {
             bool result;
 
@@ -88,10 +134,16 @@ namespace Ryujinx.Memory
             {
                 IntPtr sizeNint = new IntPtr((long)size);
 
-                result = MemoryManagementWindows.Reprotect(address, sizeNint, permission);
+                if (forView && force4KBMap)
+                {
+                    result = MemoryManagementWindows.Reprotect4KB(address, sizeNint, permission, forView);
+                }
+                else
+                {
+                    result = MemoryManagementWindows.Reprotect(address, sizeNint, permission, forView);
+                }
             }
-            else if (OperatingSystem.IsLinux() ||
-                     OperatingSystem.IsMacOS())
+            else if (OperatingSystem.IsLinux() || OperatingSystem.IsMacOS())
             {
                 result = MemoryManagementUnix.Reprotect(address, size, permission);
             }
@@ -112,8 +164,7 @@ namespace Ryujinx.Memory
             {
                 return MemoryManagementWindows.Free(address);
             }
-            else if (OperatingSystem.IsLinux() ||
-                     OperatingSystem.IsMacOS())
+            else if (OperatingSystem.IsLinux() || OperatingSystem.IsMacOS())
             {
                 return MemoryManagementUnix.Free(address);
             }
@@ -131,8 +182,7 @@ namespace Ryujinx.Memory
 
                 return MemoryManagementWindows.CreateSharedMemory(sizeNint, reserve);
             }
-            else if (OperatingSystem.IsLinux() ||
-                     OperatingSystem.IsMacOS())
+            else if (OperatingSystem.IsLinux() || OperatingSystem.IsMacOS())
             {
                 return MemoryManagementUnix.CreateSharedMemory(size, reserve);
             }
@@ -148,8 +198,7 @@ namespace Ryujinx.Memory
             {
                 MemoryManagementWindows.DestroySharedMemory(handle);
             }
-            else if (OperatingSystem.IsLinux() ||
-                     OperatingSystem.IsMacOS())
+            else if (OperatingSystem.IsLinux() || OperatingSystem.IsMacOS())
             {
                 MemoryManagementUnix.DestroySharedMemory(handle);
             }
@@ -159,16 +208,15 @@ namespace Ryujinx.Memory
             }
         }
 
-        public static IntPtr MapSharedMemory(IntPtr handle)
+        public static IntPtr MapSharedMemory(IntPtr handle, ulong size)
         {
             if (OperatingSystem.IsWindows())
             {
                 return MemoryManagementWindows.MapSharedMemory(handle);
             }
-            else if (OperatingSystem.IsLinux() ||
-                     OperatingSystem.IsMacOS())
+            else if (OperatingSystem.IsLinux() || OperatingSystem.IsMacOS())
             {
-                return MemoryManagementUnix.MapSharedMemory(handle);
+                return MemoryManagementUnix.MapSharedMemory(handle, size);
             }
             else
             {
@@ -176,29 +224,15 @@ namespace Ryujinx.Memory
             }
         }
 
-        public static void UnmapSharedMemory(IntPtr address)
+        public static void UnmapSharedMemory(IntPtr address, ulong size)
         {
             if (OperatingSystem.IsWindows())
             {
                 MemoryManagementWindows.UnmapSharedMemory(address);
             }
-            else if (OperatingSystem.IsLinux() ||
-                     OperatingSystem.IsMacOS())
+            else if (OperatingSystem.IsLinux() || OperatingSystem.IsMacOS())
             {
-                MemoryManagementUnix.UnmapSharedMemory(address);
-            }
-            else
-            {
-                throw new PlatformNotSupportedException();
-            }
-        }
-
-        public static IntPtr Remap(IntPtr target, IntPtr source, ulong size)
-        {
-            if (OperatingSystem.IsLinux() ||
-                OperatingSystem.IsMacOS())
-            {
-                return MemoryManagementUnix.Remap(target, source, size);
+                MemoryManagementUnix.UnmapSharedMemory(address, size);
             }
             else
             {

Ryujinx.Memory/MemoryManagementUnix.cs

@@ -1,8 +1,7 @@
 using System;
 using System.Collections.Concurrent;
-using System.Collections.Generic;
-using System.Runtime.InteropServices;
 using System.Runtime.Versioning;
+using System.Text;
 
 using static Ryujinx.Memory.MemoryManagerUnixHelper;
 
@@ -12,15 +11,6 @@ namespace Ryujinx.Memory
     [SupportedOSPlatform("macos")]
     static class MemoryManagementUnix
     {
-        private struct UnixSharedMemory
-        {
-            public IntPtr Pointer;
-            public ulong Size;
-            public IntPtr SourcePointer;
-        }
-
-        private static readonly List<UnixSharedMemory> _sharedMemory = new List<UnixSharedMemory>();
-        private static readonly ConcurrentDictionary<IntPtr, ulong> _sharedMemorySource = new ConcurrentDictionary<IntPtr, ulong>();
         private static readonly ConcurrentDictionary<IntPtr, ulong> _allocations = new ConcurrentDictionary<IntPtr, ulong>();
 
         public static IntPtr Allocate(ulong size)
@@ -69,40 +59,15 @@ namespace Ryujinx.Memory
 
         public static bool Commit(IntPtr address, ulong size)
         {
-            bool success = mprotect(address, size, MmapProts.PROT_READ | MmapProts.PROT_WRITE) == 0;
-
-            if (success)
-            {
-                foreach (var shared in _sharedMemory)
-                {
-                    if ((ulong)address + size > (ulong)shared.SourcePointer && (ulong)address < (ulong)shared.SourcePointer + shared.Size)
-                    {
-                        ulong sharedAddress = ((ulong)address - (ulong)shared.SourcePointer) + (ulong)shared.Pointer;
-
-                        if (mprotect((IntPtr)sharedAddress, size, MmapProts.PROT_READ | MmapProts.PROT_WRITE) != 0)
-                        {
-                            return false;
-                        }
-                    }
-                }
-            }
-
-            return success;
+            return mprotect(address, size, MmapProts.PROT_READ | MmapProts.PROT_WRITE) == 0;
         }
 
         public static bool Decommit(IntPtr address, ulong size)
         {
-            bool isShared;
-
-            lock (_sharedMemory)
-            {
-                isShared = _sharedMemory.Exists(x => (ulong)address >= (ulong)x.Pointer && (ulong)address + size <= (ulong)x.Pointer + x.Size);
-            }
-
             // Must be writable for madvise to work properly.
             mprotect(address, size, MmapProts.PROT_READ | MmapProts.PROT_WRITE);
 
-            madvise(address, size, isShared ? MADV_REMOVE : MADV_DONTNEED);
+            madvise(address, size, MADV_REMOVE);
 
             return mprotect(address, size, MmapProts.PROT_NONE) == 0;
         }
@@ -136,139 +101,83 @@ namespace Ryujinx.Memory
             return false;
         }
 
-        public static IntPtr Remap(IntPtr target, IntPtr source, ulong size)
+        public static bool Unmap(IntPtr address, ulong size)
         {
-            int flags = 1;
-
-            if (target != IntPtr.Zero)
-            {
-                flags |= 2;
-            }
-
-            IntPtr result = mremap(source, 0, size, flags, target);
-
-            if (result == IntPtr.Zero)
-            {
-                throw new InvalidOperationException();
-            }
-
-            return result;
+            return munmap(address, size) == 0;
         }
 
-        public static IntPtr CreateSharedMemory(ulong size, bool reserve)
+        public unsafe static IntPtr CreateSharedMemory(ulong size, bool reserve)
         {
-            IntPtr result = AllocateInternal(
-                size,
-                reserve ? MmapProts.PROT_NONE : MmapProts.PROT_READ | MmapProts.PROT_WRITE,
-                true);
+            int fd;
 
-            if (result == IntPtr.Zero)
+            if (OperatingSystem.IsMacOS())
+            {
+                byte[] memName = Encoding.ASCII.GetBytes("Ryujinx-XXXXXX");
+
+                fixed (byte* pMemName = memName)
+                {
+                    fd = shm_open((IntPtr)pMemName, 0x2 | 0x200 | 0x800 | 0x400, 384); // O_RDWR | O_CREAT | O_EXCL | O_TRUNC, 0600
+                    if (fd == -1)
+                    {
+                        throw new OutOfMemoryException();
+                    }
+
+                    if (shm_unlink((IntPtr)pMemName) != 0)
+                    {
+                        throw new OutOfMemoryException();
+                    }
+                }
+            }
+            else
+            {
+                byte[] fileName = Encoding.ASCII.GetBytes("/dev/shm/Ryujinx-XXXXXX");
+
+                fixed (byte* pFileName = fileName)
+                {
+                    fd = mkstemp((IntPtr)pFileName);
+                    if (fd == -1)
+                    {
+                        throw new OutOfMemoryException();
+                    }
+
+                    if (unlink((IntPtr)pFileName) != 0)
+                    {
+                        throw new OutOfMemoryException();
+                    }
+                }
+            }
+
+            if (ftruncate(fd, (IntPtr)size) != 0)
             {
                 throw new OutOfMemoryException();
             }
 
-            _sharedMemorySource[result] = (ulong)size;
-
-            return result;
+            return (IntPtr)fd;
         }
 
         public static void DestroySharedMemory(IntPtr handle)
         {
-            lock (_sharedMemory)
-            {
-                foreach (var memory in _sharedMemory)
-                {
-                    if (memory.SourcePointer == handle)
-                    {
-                        throw new InvalidOperationException("Shared memory cannot be destroyed unless fully unmapped.");
-                    }
-                }
-            }
-
-            _sharedMemorySource.Remove(handle, out ulong _);
+            close((int)handle);
         }
 
-        public static IntPtr MapSharedMemory(IntPtr handle)
+        public static IntPtr MapSharedMemory(IntPtr handle, ulong size)
         {
-            // Try find the handle for this shared memory. If it is mapped, then we want to map
-            // it a second time in another location.
-            // If it is not mapped, then its handle is the mapping.
-
-            ulong size = _sharedMemorySource[handle];
-
-            if (size == 0)
-            {
-                throw new InvalidOperationException("Shared memory cannot be mapped after its source is unmapped.");
-            }
-
-            lock (_sharedMemory)
-            {
-                foreach (var memory in _sharedMemory)
-                {
-                    if (memory.Pointer == handle)
-                    {
-                        IntPtr result = AllocateInternal(
-                            memory.Size,
-                            MmapProts.PROT_NONE
-                            );
-
-                        if (result == IntPtr.Zero)
-                        {
-                            throw new OutOfMemoryException();
-                        }
-
-                        Remap(result, handle, memory.Size);
-
-                        _sharedMemory.Add(new UnixSharedMemory
-                        {
-                            Pointer = result,
-                            Size = memory.Size,
-
-                            SourcePointer = handle
-                        });
-
-                        return result;
-                    }
-                }
-
-                _sharedMemory.Add(new UnixSharedMemory
-                {
-                    Pointer = handle,
-                    Size = size,
-
-                    SourcePointer = handle
-                });
-            }
-
-            return handle;
+            return mmap(IntPtr.Zero, size, MmapProts.PROT_READ | MmapProts.PROT_WRITE, MmapFlags.MAP_SHARED, (int)handle, 0);
         }
 
-        public static void UnmapSharedMemory(IntPtr address)
+        public static void UnmapSharedMemory(IntPtr address, ulong size)
         {
-            lock (_sharedMemory)
-            {
-                int removed = _sharedMemory.RemoveAll(memory =>
-                {
-                    if (memory.Pointer == address)
-                    {
-                        if (memory.Pointer == memory.SourcePointer)
-                        {
-                            // After removing the original mapping, it cannot be mapped again.
-                            _sharedMemorySource[memory.SourcePointer] = 0;
-                        }
+            munmap(address, size);
+        }
 
-                        Free(address);
-                        return true;
-                    }
+        public static void MapView(IntPtr sharedMemory, ulong srcOffset, IntPtr location, ulong size)
+        {
+            mmap(location, size, MmapProts.PROT_READ | MmapProts.PROT_WRITE, MmapFlags.MAP_FIXED | MmapFlags.MAP_SHARED, (int)sharedMemory, (long)srcOffset);
+        }
 
-                    return false;
-                });
-
-                if (removed == 0)
-                {
-                    throw new InvalidOperationException("Shared memory mapping could not be found.");
-                }
-            }
+        public static void UnmapView(IntPtr location, ulong size)
+        {
+            mmap(location, size, MmapProts.PROT_NONE, MmapFlags.MAP_FIXED, -1, 0);
         }
     }
 }

Ryujinx.Memory/MemoryManagementWindows.cs

@@ -1,7 +1,5 @@
 using Ryujinx.Memory.WindowsShared;
 using System;
-using System.Collections.Generic;
-using System.Runtime.InteropServices;
 using System.Runtime.Versioning;
 
 namespace Ryujinx.Memory
@@ -9,74 +7,42 @@ namespace Ryujinx.Memory
     [SupportedOSPlatform("windows")]
     static class MemoryManagementWindows
     {
-        private static readonly IntPtr InvalidHandleValue = new IntPtr(-1);
-        private static bool UseWin10Placeholders;
+        private const int PageSize = 0x1000;
 
-        private static object _emulatedHandleLock = new object();
-        private static EmulatedSharedMemoryWindows[] _emulatedShared = new EmulatedSharedMemoryWindows[64];
-        private static List<EmulatedSharedMemoryWindows> _emulatedSharedList = new List<EmulatedSharedMemoryWindows>();
-
-        [DllImport("kernel32.dll", SetLastError = true)]
-        private static extern IntPtr VirtualAlloc(
-            IntPtr lpAddress,
-            IntPtr dwSize,
-            AllocationType flAllocationType,
-            MemoryProtection flProtect);
-
-        [DllImport("kernel32.dll", SetLastError = true)]
-        private static extern bool VirtualProtect(
-            IntPtr lpAddress,
-            IntPtr dwSize,
-            MemoryProtection flNewProtect,
-            out MemoryProtection lpflOldProtect);
-
-        [DllImport("kernel32.dll", SetLastError = true)]
-        private static extern bool VirtualFree(IntPtr lpAddress, IntPtr dwSize, AllocationType dwFreeType);
-
-        [DllImport("kernel32.dll", SetLastError = true)]
-        private static extern IntPtr CreateFileMapping(
-            IntPtr hFile,
-            IntPtr lpFileMappingAttributes,
-            FileMapProtection flProtect,
-            uint dwMaximumSizeHigh,
-            uint dwMaximumSizeLow,
-            [MarshalAs(UnmanagedType.LPWStr)] string lpName);
-
-        [DllImport("kernel32.dll", SetLastError = true)]
-        private static extern bool CloseHandle(IntPtr hObject);
-
-        [DllImport("kernel32.dll", SetLastError = true)]
-        private static extern IntPtr MapViewOfFile(
-            IntPtr hFileMappingObject,
-            uint dwDesiredAccess,
-            uint dwFileOffsetHigh,
-            uint dwFileOffsetLow,
-            IntPtr dwNumberOfBytesToMap);
-
-        [DllImport("kernel32.dll", SetLastError = true)]
-        private static extern bool UnmapViewOfFile(IntPtr lpBaseAddress);
-
-        [DllImport("kernel32.dll", SetLastError = true)]
-        private static extern uint GetLastError();
-
-        static MemoryManagementWindows()
-        {
-            UseWin10Placeholders = OperatingSystem.IsWindowsVersionAtLeast(10, 0, 17134);
-        }
+        private static readonly PlaceholderManager _placeholders = new PlaceholderManager();
 
         public static IntPtr Allocate(IntPtr size)
         {
             return AllocateInternal(size, AllocationType.Reserve | AllocationType.Commit);
         }
 
-        public static IntPtr Reserve(IntPtr size)
+        public static IntPtr Reserve(IntPtr size, bool viewCompatible)
         {
+            if (viewCompatible)
+            {
+                IntPtr baseAddress = AllocateInternal2(size, AllocationType.Reserve | AllocationType.ReservePlaceholder);
+                _placeholders.ReserveRange((ulong)baseAddress, (ulong)size);
+                return baseAddress;
+            }
+
             return AllocateInternal(size, AllocationType.Reserve);
         }
 
         private static IntPtr AllocateInternal(IntPtr size, AllocationType flags = 0)
         {
-            IntPtr ptr = VirtualAlloc(IntPtr.Zero, size, flags, MemoryProtection.ReadWrite);
+            IntPtr ptr = WindowsApi.VirtualAlloc(IntPtr.Zero, size, flags, MemoryProtection.ReadWrite);
+
+            if (ptr == IntPtr.Zero)
+            {
+                throw new OutOfMemoryException();
+            }
+
+            return ptr;
+        }
+
+        private static IntPtr AllocateInternal2(IntPtr size, AllocationType flags = 0)
+        {
+            IntPtr ptr = WindowsApi.VirtualAlloc2(WindowsApi.CurrentProcessHandle, IntPtr.Zero, size, flags, MemoryProtection.NoAccess, IntPtr.Zero, 0);
 
             if (ptr == IntPtr.Zero)
             {
@@ -88,164 +54,131 @@ namespace Ryujinx.Memory
 
         public static bool Commit(IntPtr location, IntPtr size)
         {
-            if (UseWin10Placeholders)
-            {
-                lock (_emulatedSharedList)
-                {
-                    foreach (var shared in _emulatedSharedList)
-                    {
-                        if (shared.CommitMap(location, size))
-                        {
-                            return true;
-                        }
-                    }
-                }
-            }
-
-            return VirtualAlloc(location, size, AllocationType.Commit, MemoryProtection.ReadWrite) != IntPtr.Zero;
+            return WindowsApi.VirtualAlloc(location, size, AllocationType.Commit, MemoryProtection.ReadWrite) != IntPtr.Zero;
         }
 
         public static bool Decommit(IntPtr location, IntPtr size)
         {
-            if (UseWin10Placeholders)
-            {
-                lock (_emulatedSharedList)
-                {
-                    foreach (var shared in _emulatedSharedList)
-                    {
-                        if (shared.DecommitMap(location, size))
-                        {
-                            return true;
-                        }
-                    }
-                }
-            }
-
-            return VirtualFree(location, size, AllocationType.Decommit);
+            return WindowsApi.VirtualFree(location, size, AllocationType.Decommit);
         }
 
-        public static bool Reprotect(IntPtr address, IntPtr size, MemoryPermission permission)
+        public static void MapView(IntPtr sharedMemory, ulong srcOffset, IntPtr location, IntPtr size)
         {
-            if (UseWin10Placeholders)
+            _placeholders.MapView(sharedMemory, srcOffset, location, size);
+        }
+
+        public static void MapView4KB(IntPtr sharedMemory, ulong srcOffset, IntPtr location, IntPtr size)
+        {
+            ulong uaddress = (ulong)location;
+            ulong usize = (ulong)size;
+            IntPtr endLocation = (IntPtr)(uaddress + usize);
+
+            while (location != endLocation)
             {
-                ulong uaddress = (ulong)address;
-                ulong usize = (ulong)size;
-                while (usize > 0)
+                WindowsApi.VirtualFree(location, (IntPtr)PageSize, AllocationType.Release | AllocationType.PreservePlaceholder);
+
+                var ptr = WindowsApi.MapViewOfFile3(
+                    sharedMemory,
+                    WindowsApi.CurrentProcessHandle,
+                    location,
+                    srcOffset,
+                    (IntPtr)PageSize,
+                    0x4000,
+                    MemoryProtection.ReadWrite,
+                    IntPtr.Zero,
+                    0);
+
+                if (ptr == IntPtr.Zero)
                 {
-                    ulong nextGranular = (uaddress & ~EmulatedSharedMemoryWindows.MappingMask) + EmulatedSharedMemoryWindows.MappingGranularity;
-                    ulong mapSize = Math.Min(usize, nextGranular - uaddress);
-
-                    if (!VirtualProtect((IntPtr)uaddress, (IntPtr)mapSize, GetProtection(permission), out _))
-                    {
-                        return false;
-                    }
-
-                    uaddress = nextGranular;
-                    usize -= mapSize;
+                    throw new WindowsApiException("MapViewOfFile3");
                 }
 
-                return true;
+                location += PageSize;
+                srcOffset += PageSize;
+            }
+        }
+
+        public static void UnmapView(IntPtr sharedMemory, IntPtr location, IntPtr size)
+        {
+            _placeholders.UnmapView(sharedMemory, location, size);
+        }
+
+        public static void UnmapView4KB(IntPtr location, IntPtr size)
+        {
+            ulong uaddress = (ulong)location;
+            ulong usize = (ulong)size;
+            IntPtr endLocation = (IntPtr)(uaddress + usize);
+
+            while (location != endLocation)
+            {
+                bool result = WindowsApi.UnmapViewOfFile2(WindowsApi.CurrentProcessHandle, location, 2);
+                if (!result)
+                {
+                    throw new WindowsApiException("UnmapViewOfFile2");
+                }
+
+                location += PageSize;
+            }
+        }
+
+        public static bool Reprotect(IntPtr address, IntPtr size, MemoryPermission permission, bool forView)
+        {
+            if (forView)
+            {
+                return _placeholders.ReprotectView(address, size, permission);
             }
             else
             {
-                return VirtualProtect(address, size, GetProtection(permission), out _);
+                return WindowsApi.VirtualProtect(address, size, WindowsApi.GetProtection(permission), out _);
             }
         }
 
-        private static MemoryProtection GetProtection(MemoryPermission permission)
+        public static bool Reprotect4KB(IntPtr address, IntPtr size, MemoryPermission permission, bool forView)
         {
-            return permission switch
+            ulong uaddress = (ulong)address;
+            ulong usize = (ulong)size;
+            while (usize > 0)
             {
-                MemoryPermission.None => MemoryProtection.NoAccess,
-                MemoryPermission.Read => MemoryProtection.ReadOnly,
-                MemoryPermission.ReadAndWrite => MemoryProtection.ReadWrite,
-                MemoryPermission.ReadAndExecute => MemoryProtection.ExecuteRead,
-                MemoryPermission.ReadWriteExecute => MemoryProtection.ExecuteReadWrite,
-                MemoryPermission.Execute => MemoryProtection.Execute,
-                _ => throw new MemoryProtectionException(permission)
-            };
+                if (!WindowsApi.VirtualProtect((IntPtr)uaddress, (IntPtr)PageSize, WindowsApi.GetProtection(permission), out _))
+                {
+                    return false;
+                }
+
+                uaddress += PageSize;
+                usize -= PageSize;
+            }
+
+            return true;
         }
 
         public static bool Free(IntPtr address)
         {
-            return VirtualFree(address, IntPtr.Zero, AllocationType.Release);
-        }
-
-        private static int GetEmulatedHandle()
-        {
-            // Assumes we have the handle lock.
-
-            for (int i = 0; i < _emulatedShared.Length; i++)
-            {
-                if (_emulatedShared[i] == null)
-                {
-                    return i + 1;
-                }
-            }
-
-            throw new InvalidProgramException("Too many shared memory handles were created.");
-        }
-
-        public static bool EmulatedHandleValid(ref int handle)
-        {
-            handle--;
-            return handle >= 0 && handle < _emulatedShared.Length && _emulatedShared[handle] != null;
+            return WindowsApi.VirtualFree(address, IntPtr.Zero, AllocationType.Release);
         }
 
         public static IntPtr CreateSharedMemory(IntPtr size, bool reserve)
         {
-            if (UseWin10Placeholders && reserve)
+            var prot = reserve ? FileMapProtection.SectionReserve : FileMapProtection.SectionCommit;
+
+            IntPtr handle = WindowsApi.CreateFileMapping(
+                WindowsApi.InvalidHandleValue,
+                IntPtr.Zero,
+                FileMapProtection.PageReadWrite | prot,
+                (uint)(size.ToInt64() >> 32),
+                (uint)size.ToInt64(),
+                null);
+
+            if (handle == IntPtr.Zero)
             {
-                lock (_emulatedHandleLock)
-                {
-                    int handle = GetEmulatedHandle();
-                    _emulatedShared[handle - 1] = new EmulatedSharedMemoryWindows((ulong)size);
-                    _emulatedSharedList.Add(_emulatedShared[handle - 1]);
-
-                    return (IntPtr)handle;
-                }
+                throw new OutOfMemoryException();
             }
-            else
-            {
-                var prot = reserve ? FileMapProtection.SectionReserve : FileMapProtection.SectionCommit;
 
-                IntPtr handle = CreateFileMapping(
-                    InvalidHandleValue,
-                    IntPtr.Zero,
-                    FileMapProtection.PageReadWrite | prot,
-                    (uint)(size.ToInt64() >> 32),
-                    (uint)size.ToInt64(),
-                    null);
-
-                if (handle == IntPtr.Zero)
-                {
-                    throw new OutOfMemoryException();
-                }
-
-                return handle;
-            }
+            return handle;
         }
 
         public static void DestroySharedMemory(IntPtr handle)
         {
-            if (UseWin10Placeholders)
-            {
-                lock (_emulatedHandleLock)
-                {
-                    int iHandle = (int)(ulong)handle;
-
-                    if (EmulatedHandleValid(ref iHandle))
-                    {
-                        _emulatedSharedList.Remove(_emulatedShared[iHandle]);
-                        _emulatedShared[iHandle].Dispose();
-                        _emulatedShared[iHandle] = null;
-
-                        return;
-                    }
-                }
-            }
-
-            if (!CloseHandle(handle))
+            if (!WindowsApi.CloseHandle(handle))
             {
                 throw new ArgumentException("Invalid handle.", nameof(handle));
             }
@@ -253,20 +186,7 @@ namespace Ryujinx.Memory
 
         public static IntPtr MapSharedMemory(IntPtr handle)
         {
-            if (UseWin10Placeholders)
-            {
-                lock (_emulatedHandleLock)
-                {
-                    int iHandle = (int)(ulong)handle;
-
-                    if (EmulatedHandleValid(ref iHandle))
-                    {
-                        return _emulatedShared[iHandle].Map();
-                    }
-                }
-            }
-
-            IntPtr ptr = MapViewOfFile(handle, 4 | 2, 0, 0, IntPtr.Zero);
+            IntPtr ptr = WindowsApi.MapViewOfFile(handle, 4 | 2, 0, 0, IntPtr.Zero);
 
             if (ptr == IntPtr.Zero)
             {
@@ -278,24 +198,15 @@ namespace Ryujinx.Memory
 
         public static void UnmapSharedMemory(IntPtr address)
         {
-            if (UseWin10Placeholders)
-            {
-                lock (_emulatedHandleLock)
-                {
-                    foreach (EmulatedSharedMemoryWindows shared in _emulatedSharedList)
-                    {
-                        if (shared.Unmap((ulong)address))
-                        {
-                            return;
-                        }
-                    }
-                }
-            }
-
-            if (!UnmapViewOfFile(address))
+            if (!WindowsApi.UnmapViewOfFile(address))
             {
                 throw new ArgumentException("Invalid address.", nameof(address));
             }
         }
+
+        public static bool RetryFromAccessViolation()
+        {
+            return _placeholders.RetryFromAccessViolation();
+        }
     }
 }

Ryujinx.Memory/MemoryManagerUnixHelper.cs

@@ -21,7 +21,23 @@ namespace Ryujinx.Memory
             MAP_PRIVATE = 2,
             MAP_ANONYMOUS = 4,
             MAP_NORESERVE = 8,
-            MAP_UNLOCKED = 16
+            MAP_FIXED = 16,
+            MAP_UNLOCKED = 32
+        }
+
+        [Flags]
+        public enum OpenFlags : uint
+        {
+            O_RDONLY = 0,
+            O_WRONLY = 1,
+            O_RDWR = 2,
+            O_CREAT = 4,
+            O_EXCL = 8,
+            O_NOCTTY = 16,
+            O_TRUNC = 32,
+            O_APPEND = 64,
+            O_NONBLOCK = 128,
+            O_SYNC = 256,
         }
 
         private const int MAP_ANONYMOUS_LINUX_GENERIC = 0x20;
@@ -50,6 +66,24 @@ namespace Ryujinx.Memory
         [DllImport("libc", SetLastError = true)]
         public static extern int madvise(IntPtr address, ulong size, int advice);
 
+        [DllImport("libc", SetLastError = true)]
+        public static extern int mkstemp(IntPtr template);
+
+        [DllImport("libc", SetLastError = true)]
+        public static extern int unlink(IntPtr pathname);
+
+        [DllImport("libc", SetLastError = true)]
+        public static extern int ftruncate(int fildes, IntPtr length);
+
+        [DllImport("libc", SetLastError = true)]
+        public static extern int close(int fd);
+
+        [DllImport("libc", SetLastError = true)]
+        public static extern int shm_open(IntPtr name, int oflag, uint mode);
+
+        [DllImport("libc", SetLastError = true)]
+        public static extern int shm_unlink(IntPtr name);
+
         private static int MmapFlagsToSystemFlags(MmapFlags flags)
         {
             int result = 0;
@@ -64,6 +98,11 @@ namespace Ryujinx.Memory
                 result |= (int)MmapFlags.MAP_PRIVATE;
             }
 
+            if (flags.HasFlag(MmapFlags.MAP_FIXED))
+            {
+                result |= (int)MmapFlags.MAP_FIXED;
+            }
+
             if (flags.HasFlag(MmapFlags.MAP_ANONYMOUS))
             {
                 if (OperatingSystem.IsLinux())

Ryujinx.Memory/PageTable.cs

@@ -1,6 +1,6 @@
 namespace Ryujinx.Memory
 {
-    class PageTable<T> where T : unmanaged
+    public class PageTable<T> where T : unmanaged
     {
         public const int PageBits = 12;
         public const int PageSize = 1 << PageBits;

Ryujinx.Memory/Range/HostMemoryRange.cs

@@ -1,71 +0,0 @@
-using System;
-
-namespace Ryujinx.Memory.Range
-{
-    /// <summary>
-    /// Range of memory composed of an address and size.
-    /// </summary>
-    public struct HostMemoryRange : IEquatable<HostMemoryRange>
-    {
-        /// <summary>
-        /// An empty memory range, with a null address and zero size.
-        /// </summary>
-        public static HostMemoryRange Empty => new HostMemoryRange(0, 0);
-
-        /// <summary>
-        /// Start address of the range.
-        /// </summary>
-        public nuint Address { get; }
-
-        /// <summary>
-        /// Size of the range in bytes.
-        /// </summary>
-        public ulong Size { get; }
-
-        /// <summary>
-        /// Address where the range ends (exclusive).
-        /// </summary>
-        public nuint EndAddress => Address + (nuint)Size;
-
-        /// <summary>
-        /// Creates a new memory range with the specified address and size.
-        /// </summary>
-        /// <param name="address">Start address</param>
-        /// <param name="size">Size in bytes</param>
-        public HostMemoryRange(nuint address, ulong size)
-        {
-            Address = address;
-            Size = size;
-        }
-
-        /// <summary>
-        /// Checks if the range overlaps with another.
-        /// </summary>
-        /// <param name="other">The other range to check for overlap</param>
-        /// <returns>True if the ranges overlap, false otherwise</returns>
-        public bool OverlapsWith(HostMemoryRange other)
-        {
-            nuint thisAddress = Address;
-            nuint thisEndAddress = EndAddress;
-            nuint otherAddress = other.Address;
-            nuint otherEndAddress = other.EndAddress;
-
-            return thisAddress < otherEndAddress && otherAddress < thisEndAddress;
-        }
-
-        public override bool Equals(object obj)
-        {
-            return obj is HostMemoryRange other && Equals(other);
-        }
-
-        public bool Equals(HostMemoryRange other)
-        {
-            return Address == other.Address && Size == other.Size;
-        }
-
-        public override int GetHashCode()
-        {
-            return HashCode.Combine(Address, Size);
-        }
-    }
-}

Ryujinx.Memory/Tracking/MemoryTracking.cs

@@ -188,6 +188,30 @@ namespace Ryujinx.Memory.Tracking
             return VirtualMemoryEvent(address, 1, write);
         }
 
+        /// <summary>
+        /// Signal that a virtual memory event happened at the given location.
+        /// This is similar VirtualMemoryEvent, but on Windows, it might also return true after a partial unmap.
+        /// This should only be called from the exception handler.
+        /// </summary>
+        /// <param name="address">Virtual address accessed</param>
+        /// <param name="size">Size of the region affected in bytes</param>
+        /// <param name="write">Whether the region was written to or read</param>
+        /// <param name="precise">True if the access is precise, false otherwise</param>
+        /// <returns>True if the event triggered any tracking regions, false otherwise</returns>
+        public bool VirtualMemoryEventEh(ulong address, ulong size, bool write, bool precise = false)
+        {
+            // Windows has a limitation, it can't do partial unmaps.
+            // For this reason, we need to unmap the whole range and then remap the sub-ranges.
+            // When this happens, we might have caused a undesirable access violation from the time that the range was unmapped.
+            // In this case, try again as the memory might be mapped now.
+            if (OperatingSystem.IsWindows() && MemoryManagementWindows.RetryFromAccessViolation())
+            {
+                return true;
+            }
+
+            return VirtualMemoryEvent(address, size, write, precise);
+        }
+
         /// <summary>
         /// Signal that a virtual memory event happened at the given location.
         /// This can be flagged as a precise event, which will avoid reprotection and call special handlers if possible.

Ryujinx.Memory/WindowsShared/EmulatedSharedMemoryWindows.cs

@@ -1,703 +0,0 @@
-using Ryujinx.Memory.Range;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Runtime.InteropServices;
-
-namespace Ryujinx.Memory.WindowsShared
-{
-    class EmulatedSharedMemoryWindows : IDisposable
-    {
-        private static readonly IntPtr InvalidHandleValue = new IntPtr(-1);
-        private static readonly IntPtr CurrentProcessHandle = new IntPtr(-1);
-
-        public const int MappingBits = 16; // Windows 64kb granularity.
-        public const ulong MappingGranularity = 1 << MappingBits;
-        public const ulong MappingMask = MappingGranularity - 1;
-
-        public const ulong BackingSize32GB = 32UL * 1024UL * 1024UL * 1024UL; // Reasonable max size of 32GB.
-
-        private class SharedMemoryMapping : INonOverlappingRange
-        {
-            public ulong Address { get; }
-
-            public ulong Size { get; private set; }
-
-            public ulong EndAddress { get; private set; }
-
-            public List<int> Blocks;
-
-            public SharedMemoryMapping(ulong address, ulong size, List<int> blocks = null)
-            {
-                Address = address;
-                Size = size;
-                EndAddress = address + size;
-
-                Blocks = blocks ?? new List<int>();
-            }
-
-            public bool OverlapsWith(ulong address, ulong size)
-            {
-                return Address < address + size && address < EndAddress;
-            }
-
-            public void ExtendTo(ulong endAddress, RangeList<SharedMemoryMapping> list)
-            {
-                EndAddress = endAddress;
-                Size = endAddress - Address;
-
-                list.UpdateEndAddress(this);
-            }
-
-            public void AddBlocks(IEnumerable<int> blocks)
-            {
-                if (Blocks.Count > 0 && blocks.Count() > 0 && Blocks.Last() == blocks.First())
-                {
-                    Blocks.AddRange(blocks.Skip(1));
-                }
-                else
-                {
-                    Blocks.AddRange(blocks);
-                }
-            }
-
-            public INonOverlappingRange Split(ulong splitAddress)
-            {
-                SharedMemoryMapping newRegion = new SharedMemoryMapping(splitAddress, EndAddress - splitAddress);
-
-                int end = (int)((EndAddress + MappingMask) >> MappingBits);
-                int start = (int)(Address >> MappingBits);
-
-                Size = splitAddress - Address;
-                EndAddress = splitAddress;
-
-                int splitEndBlock = (int)((splitAddress + MappingMask) >> MappingBits);
-                int splitStartBlock = (int)(splitAddress >> MappingBits);
-
-                newRegion.AddBlocks(Blocks.Skip(splitStartBlock - start));
-                Blocks.RemoveRange(splitEndBlock - start, end - splitEndBlock);
-
-                return newRegion;
-            }
-        }
-
-        [DllImport("kernel32.dll", SetLastError = true)]
-        private static extern IntPtr CreateFileMapping(
-            IntPtr hFile,
-            IntPtr lpFileMappingAttributes,
-            FileMapProtection flProtect,
-            uint dwMaximumSizeHigh,
-            uint dwMaximumSizeLow,
-            [MarshalAs(UnmanagedType.LPWStr)] string lpName);
-
-        [DllImport("kernel32.dll", SetLastError = true)]
-        private static extern bool CloseHandle(IntPtr hObject);
-
-        [DllImport("KernelBase.dll", SetLastError = true)]
-        private static extern IntPtr VirtualAlloc2(
-            IntPtr process,
-            IntPtr lpAddress,
-            IntPtr dwSize,
-            AllocationType flAllocationType,
-            MemoryProtection flProtect,
-            IntPtr extendedParameters,
-            ulong parameterCount);
-
-        [DllImport("kernel32.dll", SetLastError = true)]
-        private static extern bool VirtualFree(IntPtr lpAddress, IntPtr dwSize, AllocationType dwFreeType);
-
-        [DllImport("KernelBase.dll", SetLastError = true)]
-        private static extern IntPtr MapViewOfFile3(
-            IntPtr hFileMappingObject,
-            IntPtr process,
-            IntPtr baseAddress,
-            ulong offset,
-            IntPtr dwNumberOfBytesToMap,
-            ulong allocationType,
-            MemoryProtection dwDesiredAccess,
-            IntPtr extendedParameters,
-            ulong parameterCount);
-
-        [DllImport("KernelBase.dll", SetLastError = true)]
-        private static extern bool UnmapViewOfFile2(IntPtr process, IntPtr lpBaseAddress, ulong unmapFlags);
-
-        private ulong _size;
-
-        private object _lock = new object();
-
-        private ulong _backingSize;
-        private IntPtr _backingMemHandle;
-        private int _backingEnd;
-        private int _backingAllocated;
-        private Queue<int> _backingFreeList;
-
-        private List<ulong> _mappedBases;
-        private RangeList<SharedMemoryMapping> _mappings;
-        private SharedMemoryMapping[] _foundMappings = new SharedMemoryMapping[32];
-        private PlaceholderList _placeholders;
-
-        public EmulatedSharedMemoryWindows(ulong size)
-        {
-            ulong backingSize = BackingSize32GB;
-
-            _size = size;
-            _backingSize = backingSize;
-
-            _backingMemHandle = CreateFileMapping(
-                InvalidHandleValue,
-                IntPtr.Zero,
-                FileMapProtection.PageReadWrite | FileMapProtection.SectionReserve,
-                (uint)(backingSize >> 32),
-                (uint)backingSize,
-                null);
-
-            if (_backingMemHandle == IntPtr.Zero)
-            {
-                throw new OutOfMemoryException();
-            }
-
-            _backingFreeList = new Queue<int>();
-            _mappings = new RangeList<SharedMemoryMapping>();
-            _mappedBases = new List<ulong>();
-            _placeholders = new PlaceholderList(size >> MappingBits);
-        }
-
-        private (ulong granularStart, ulong granularEnd) GetAlignedRange(ulong address, ulong size)
-        {
-            return (address & (~MappingMask), (address + size + MappingMask) & (~MappingMask));
-        }
-
-        private void Commit(ulong address, ulong size)
-        {
-            (ulong granularStart, ulong granularEnd) = GetAlignedRange(address, size);
-
-            ulong endAddress = address + size;
-
-            lock (_lock)
-            {
-                // Search a bit before and after the new mapping.
-                // When adding our new mapping, we may need to join an existing mapping into our new mapping (or in some cases, to the other side!)
-                ulong searchStart = granularStart == 0 ? 0 : (granularStart - 1);
-                int mappingCount = _mappings.FindOverlapsNonOverlapping(searchStart, (granularEnd - searchStart) + 1, ref _foundMappings);
-
-                int first = -1;
-                int last = -1;
-                SharedMemoryMapping startOverlap = null;
-                SharedMemoryMapping endOverlap = null;
-
-                int lastIndex = (int)(address >> MappingBits);
-                int endIndex = (int)((endAddress + MappingMask) >> MappingBits);
-                int firstBlock = -1;
-                int endBlock = -1;
-
-                for (int i = 0; i < mappingCount; i++)
-                {
-                    SharedMemoryMapping mapping = _foundMappings[i];
-
-                    if (mapping.Address < address)
-                    {
-                        if (mapping.EndAddress >= address)
-                        {
-                            startOverlap = mapping;
-                        }
-
-                        if ((int)((mapping.EndAddress - 1) >> MappingBits) == lastIndex)
-                        {
-                            lastIndex = (int)((mapping.EndAddress + MappingMask) >> MappingBits);
-                            firstBlock = mapping.Blocks.Last();
-                        }
-                    }
-
-                    if (mapping.EndAddress > endAddress)
-                    {
-                        if (mapping.Address <= endAddress)
-                        {
-                            endOverlap = mapping;
-                        }
-
-                        if ((int)((mapping.Address) >> MappingBits) + 1 == endIndex)
-                        {
-                            endIndex = (int)((mapping.Address) >> MappingBits);
-                            endBlock = mapping.Blocks.First();
-                        }
-                    }
-
-                    if (mapping.OverlapsWith(address, size))
-                    {
-                        if (first == -1)
-                        {
-                            first = i;
-                        }
-
-                        last = i;
-                    }
-                }
-
-                if (startOverlap == endOverlap && startOverlap != null)
-                {
-                    // Already fully committed.
-                    return;
-                }
-
-                var blocks = new List<int>();
-                int lastBlock = -1;
-
-                if (firstBlock != -1)
-                {
-                    blocks.Add(firstBlock);
-                    lastBlock = firstBlock;
-                }
-
-                bool hasMapped = false;
-                Action map = () =>
-                {
-                    if (!hasMapped)
-                    {
-                        _placeholders.EnsurePlaceholders(address >> MappingBits, (granularEnd - granularStart) >> MappingBits, SplitPlaceholder);
-                        hasMapped = true;
-                    }
-
-                    // There's a gap between this index and the last. Allocate blocks to fill it.
-                    blocks.Add(MapBackingBlock(MappingGranularity * (ulong)lastIndex++));
-                };
-
-                if (first != -1)
-                {
-                    for (int i = first; i <= last; i++)
-                    {
-                        SharedMemoryMapping mapping = _foundMappings[i];
-                        int mapIndex = (int)(mapping.Address >> MappingBits);
-
-                        while (lastIndex < mapIndex)
-                        {
-                            map();
-                        }
-
-                        if (lastBlock == mapping.Blocks[0])
-                        {
-                            blocks.AddRange(mapping.Blocks.Skip(1));
-                        }
-                        else
-                        {
-                            blocks.AddRange(mapping.Blocks);
-                        }
-
-                        lastIndex = (int)((mapping.EndAddress - 1) >> MappingBits) + 1;
-                    }
-                }
-
-                while (lastIndex < endIndex)
-                {
-                    map();
-                }
-
-                if (endBlock != -1 && endBlock != lastBlock)
-                {
-                    blocks.Add(endBlock);
-                }
-
-                if (startOverlap != null && endOverlap != null)
-                {
-                    // Both sides should be coalesced. Extend the start overlap to contain the end overlap, and add together their blocks.
-
-                    _mappings.Remove(endOverlap);
-
-                    startOverlap.ExtendTo(endOverlap.EndAddress, _mappings);
-
-                    startOverlap.AddBlocks(blocks);
-                    startOverlap.AddBlocks(endOverlap.Blocks);
-                }
-                else if (startOverlap != null)
-                {
-                    startOverlap.ExtendTo(endAddress, _mappings);
-
-                    startOverlap.AddBlocks(blocks);
-                }
-                else
-                {
-                    var mapping = new SharedMemoryMapping(address, size, blocks);
-
-                    if (endOverlap != null)
-                    {
-                        mapping.ExtendTo(endOverlap.EndAddress, _mappings);
-
-                        mapping.AddBlocks(endOverlap.Blocks);
-
-                        _mappings.Remove(endOverlap);
-                    }
-
-                    _mappings.Add(mapping);
-                }
-            }
-        }
-
-        private void Decommit(ulong address, ulong size)
-        {
-            (ulong granularStart, ulong granularEnd) = GetAlignedRange(address, size);
-            ulong endAddress = address + size;
-
-            lock (_lock)
-            {
-                int mappingCount = _mappings.FindOverlapsNonOverlapping(granularStart, granularEnd - granularStart, ref _foundMappings);
-
-                int first = -1;
-                int last = -1;
-
-                for (int i = 0; i < mappingCount; i++)
-                {
-                    SharedMemoryMapping mapping = _foundMappings[i];
-
-                    if (mapping.OverlapsWith(address, size))
-                    {
-                        if (first == -1)
-                        {
-                            first = i;
-                        }
-
-                        last = i;
-                    }
-                }
-
-                if (first == -1)
-                {
-                    return; // Could not find any regions to decommit.
-                }
-
-                int lastReleasedBlock = -1;
-
-                bool releasedFirst = false;
-                bool releasedLast = false;
-
-                for (int i = last; i >= first; i--)
-                {
-                    SharedMemoryMapping mapping = _foundMappings[i];
-                    bool releaseEnd = true;
-                    bool releaseStart = true;
-
-                    if (i == last)
-                    {
-                        // If this is the last region, do not release the block if there is a page ahead of us, or the block continues after us. (it is keeping the block alive)
-                        releaseEnd = last == mappingCount - 1;
-
-                        // If the end region starts after the decommit end address, split and readd it after modifying its base address.
-                        if (mapping.EndAddress > endAddress)
-                        {
-                            var newMapping = (SharedMemoryMapping)mapping.Split(endAddress);
-                            _mappings.UpdateEndAddress(mapping);
-                            _mappings.Add(newMapping);
-
-                            if ((endAddress & MappingMask) != 0)
-                            {
-                                releaseEnd = false;
-                            }
-                        }
-
-                        releasedLast = releaseEnd;
-                    }
-
-                    if (i == first)
-                    {
-                        // If this is the first region, do not release the block if there is a region behind us. (it is keeping the block alive)
-                        releaseStart = first == 0;
-
-                        // If the first region starts before the decommit address, split it by modifying its end address.
-                        if (mapping.Address < address)
-                        {
-                            var oldMapping = mapping;
-                            mapping = (SharedMemoryMapping)mapping.Split(address);
-                            _mappings.UpdateEndAddress(oldMapping);
-
-                            if ((address & MappingMask) != 0)
-                            {
-                                releaseStart = false;
-                            }
-                        }
-
-                        releasedFirst = releaseStart;
-                    }
-
-                    _mappings.Remove(mapping);
-
-                    ulong releasePointer = (mapping.EndAddress + MappingMask) & (~MappingMask);
-                    for (int j = mapping.Blocks.Count - 1; j >= 0; j--)
-                    {
-                        int blockId = mapping.Blocks[j];
-
-                        releasePointer -= MappingGranularity;
-
-                        if (lastReleasedBlock == blockId)
-                        {
-                            // When committed regions are fragmented, multiple will have the same block id for their start/end granular block.
-                            // Avoid releasing these blocks twice.
-                            continue;
-                        }
-
-                        if ((j != 0 || releaseStart) && (j != mapping.Blocks.Count - 1 || releaseEnd))
-                        {
-                            ReleaseBackingBlock(releasePointer, blockId);
-                        }
-
-                        lastReleasedBlock = blockId;
-                    }
-                }
-
-                ulong placeholderStart = (granularStart >> MappingBits) + (releasedFirst ? 0UL : 1UL);
-                ulong placeholderEnd = (granularEnd >> MappingBits) - (releasedLast ? 0UL : 1UL);
-
-                if (placeholderEnd > placeholderStart)
-                {
-                    _placeholders.RemovePlaceholders(placeholderStart, placeholderEnd - placeholderStart, CoalescePlaceholder);
-                }
-            }
-        }
-
-        public bool CommitMap(IntPtr address, IntPtr size)
-        {
-            lock (_lock)
-            {
-                foreach (ulong mapping in _mappedBases)
-                {
-                    ulong offset = (ulong)address - mapping;
-
-                    if (offset < _size)
-                    {
-                        Commit(offset, (ulong)size);
-                        return true;
-                    }
-                }
-            }
-
-            return false;
-        }
-
-        public bool DecommitMap(IntPtr address, IntPtr size)
-        {
-            lock (_lock)
-            {
-                foreach (ulong mapping in _mappedBases)
-                {
-                    ulong offset = (ulong)address - mapping;
-
-                    if (offset < _size)
-                    {
-                        Decommit(offset, (ulong)size);
-                        return true;
-                    }
-                }
-            }
-
-            return false;
-        }
-
-        private int MapBackingBlock(ulong offset)
-        {
-            bool allocate = false;
-            int backing;
-
-            if (_backingFreeList.Count > 0)
-            {
-                backing = _backingFreeList.Dequeue();
-            }
-            else
-            {
-                if (_backingAllocated == _backingEnd)
-                {
-                    // Allocate the backing.
-                    _backingAllocated++;
-                    allocate = true;
-                }
-
-                backing = _backingEnd++;
-            }
-
-            ulong backingOffset = MappingGranularity * (ulong)backing;
-
-            foreach (ulong baseAddress in _mappedBases)
-            {
-                CommitToMap(baseAddress, offset, MappingGranularity, backingOffset, allocate);
-                allocate = false;
-            }
-
-            return backing;
-        }
-
-        private void ReleaseBackingBlock(ulong offset, int id)
-        {
-            foreach (ulong baseAddress in _mappedBases)
-            {
-                DecommitFromMap(baseAddress, offset);
-            }
-
-            if (_backingEnd - 1 == id)
-            {
-                _backingEnd = id;
-            }
-            else
-            {
-                _backingFreeList.Enqueue(id);
-            }
-        }
-
-        public IntPtr Map()
-        {
-            IntPtr newMapping = VirtualAlloc2(
-                CurrentProcessHandle,
-                IntPtr.Zero,
-                (IntPtr)_size,
-                AllocationType.Reserve | AllocationType.ReservePlaceholder,
-                MemoryProtection.NoAccess,
-                IntPtr.Zero,
-                0);
-
-            if (newMapping == IntPtr.Zero)
-            {
-                throw new OutOfMemoryException();
-            }
-
-            // Apply all existing mappings to the new mapping
-            lock (_lock)
-            {
-                int lastBlock = -1;
-                foreach (SharedMemoryMapping mapping in _mappings)
-                {
-                    ulong blockAddress = mapping.Address & (~MappingMask);
-                    foreach (int block in mapping.Blocks)
-                    {
-                        if (block != lastBlock)
-                        {
-                            ulong backingOffset = MappingGranularity * (ulong)block;
-
-                            CommitToMap((ulong)newMapping, blockAddress, MappingGranularity, backingOffset, false);
-
-                            lastBlock = block;
-                        }
-
-                        blockAddress += MappingGranularity;
-                    }
-                }
-
-                _mappedBases.Add((ulong)newMapping);
-            }
-
-            return newMapping;
-        }
-
-        private void SplitPlaceholder(ulong address, ulong size)
-        {
-            ulong byteAddress = address << MappingBits;
-            IntPtr byteSize = (IntPtr)(size << MappingBits);
-
-            foreach (ulong mapAddress in _mappedBases)
-            {
-                bool result = VirtualFree((IntPtr)(mapAddress + byteAddress), byteSize, AllocationType.PreservePlaceholder | AllocationType.Release);
-
-                if (!result)
-                {
-                    throw new InvalidOperationException("Placeholder could not be split.");
-                }
-            }
-        }
-
-        private void CoalescePlaceholder(ulong address, ulong size)
-        {
-            ulong byteAddress = address << MappingBits;
-            IntPtr byteSize = (IntPtr)(size << MappingBits);
-
-            foreach (ulong mapAddress in _mappedBases)
-            {
-                bool result = VirtualFree((IntPtr)(mapAddress + byteAddress), byteSize, AllocationType.CoalescePlaceholders | AllocationType.Release);
-
-                if (!result)
-                {
-                    throw new InvalidOperationException("Placeholder could not be coalesced.");
-                }
-            }
-        }
-
-        private void CommitToMap(ulong mapAddress, ulong address, ulong size, ulong backingOffset, bool allocate)
-        {
-            IntPtr targetAddress = (IntPtr)(mapAddress + address);
-
-            // Assume the placeholder worked (or already exists)
-            // Map the backing memory into the mapped location.
-
-            IntPtr mapped = MapViewOfFile3(
-                _backingMemHandle,
-                CurrentProcessHandle,
-                targetAddress,
-                backingOffset,
-                (IntPtr)MappingGranularity,
-                0x4000, // REPLACE_PLACEHOLDER
-                MemoryProtection.ReadWrite,
-                IntPtr.Zero,
-                0);
-
-            if (mapped == IntPtr.Zero)
-            {
-                throw new InvalidOperationException($"Could not map view of backing memory. (va=0x{address:X16} size=0x{size:X16}, error code {Marshal.GetLastWin32Error()})");
-            }
-
-            if (allocate)
-            {
-                // Commit this part of the shared memory.
-                VirtualAlloc2(CurrentProcessHandle, targetAddress, (IntPtr)MappingGranularity, AllocationType.Commit, MemoryProtection.ReadWrite, IntPtr.Zero, 0);
-            }
-        }
-
-        private void DecommitFromMap(ulong baseAddress, ulong address)
-        {
-            UnmapViewOfFile2(CurrentProcessHandle, (IntPtr)(baseAddress + address), 2);
-        }
-
-        public bool Unmap(ulong baseAddress)
-        {
-            lock (_lock)
-            {
-                if (_mappedBases.Remove(baseAddress))
-                {
-                    int lastBlock = -1;
-
-                    foreach (SharedMemoryMapping mapping in _mappings)
-                    {
-                        ulong blockAddress = mapping.Address & (~MappingMask);
-                        foreach (int block in mapping.Blocks)
-                        {
-                            if (block != lastBlock)
-                            {
-                                DecommitFromMap(baseAddress, blockAddress);
-
-                                lastBlock = block;
-                            }
-
-                            blockAddress += MappingGranularity;
-                        }
-                    }
-
-                    if (!VirtualFree((IntPtr)baseAddress, (IntPtr)0, AllocationType.Release))
-                    {
-                        throw new InvalidOperationException("Couldn't free mapping placeholder.");
-                    }
-
-                    return true;
-                }
-
-                return false;
-            }
-        }
-
-        public void Dispose()
-        {
-            // Remove all file mappings
-            lock (_lock)
-            {
-                foreach (ulong baseAddress in _mappedBases.ToArray())
-                {
-                    Unmap(baseAddress);
-                }
-            }
-
-            // Finally, delete the file mapping.
-            CloseHandle(_backingMemHandle);
-        }
-    }
-}

Ryujinx.Memory/WindowsShared/IntervalTree.cs

@@ -0,0 +1,740 @@
+using System;
+using System.Collections.Generic;
+
+namespace Ryujinx.Memory.WindowsShared
+{
+    /// <summary>
+    /// An Augmented Interval Tree based off of the "TreeDictionary"'s Red-Black Tree. Allows fast overlap checking of ranges.
+    /// </summary>
+    /// <typeparam name="K">Key</typeparam>
+    /// <typeparam name="V">Value</typeparam>
+    class IntervalTree<K, V> where K : IComparable<K>
+    {
+        private const int ArrayGrowthSize = 32;
+
+        private const bool Black = true;
+        private const bool Red = false;
+        private IntervalTreeNode<K, V> _root = null;
+        private int _count = 0;
+
+        public int Count => _count;
+
+        public IntervalTree() { }
+
+        #region Public Methods
+
+        /// <summary>
+        /// Gets the values of the interval whose key is <paramref name="key"/>.
+        /// </summary>
+        /// <param name="key">Key of the node value to get</param>
+        /// <param name="value">Value with the given <paramref name="key"/></param>
+        /// <returns>True if the key is on the dictionary, false otherwise</returns>
+        public bool TryGet(K key, out V value)
+        {
+            IntervalTreeNode<K, V> node = GetNode(key);
+
+            if (node == null)
+            {
+                value = default;
+                return false;
+            }
+
+            value = node.Value;
+            return true;
+        }
+
+        /// <summary>
+        /// Returns the start addresses of the intervals whose start and end keys overlap the given range.
+        /// </summary>
+        /// <param name="start">Start of the range</param>
+        /// <param name="end">End of the range</param>
+        /// <param name="overlaps">Overlaps array to place results in</param>
+        /// <param name="overlapCount">Index to start writing results into the array. Defaults to 0</param>
+        /// <returns>Number of intervals found</returns>
+        public int Get(K start, K end, ref IntervalTreeNode<K, V>[] overlaps, int overlapCount = 0)
+        {
+            GetNodes(_root, start, end, ref overlaps, ref overlapCount);
+
+            return overlapCount;
+        }
+
+        /// <summary>
+        /// Adds a new interval into the tree whose start is <paramref name="start"/>, end is <paramref name="end"/> and value is <paramref name="value"/>.
+        /// </summary>
+        /// <param name="start">Start of the range to add</param>
+        /// <param name="end">End of the range to insert</param>
+        /// <param name="value">Value to add</param>
+        /// <exception cref="ArgumentNullException"><paramref name="value"/> is null</exception>
+        public void Add(K start, K end, V value)
+        {
+            if (value == null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+
+            BSTInsert(start, end, value, null, out _);
+        }
+
+        /// <summary>
+        /// Removes a value from the tree, searching for it with <paramref name="key"/>.
+        /// </summary>
+        /// <param name="key">Key of the node to remove</param>
+        /// <returns>Number of deleted values</returns>
+        public int Remove(K key)
+        {
+            return Remove(GetNode(key));
+        }
+
+        /// <summary>
+        /// Removes a value from the tree, searching for it with <paramref name="key"/>.
+        /// </summary>
+        /// <param name="nodeToDelete">Node to be removed</param>
+        /// <returns>Number of deleted values</returns>
+        public int Remove(IntervalTreeNode<K, V> nodeToDelete)
+        {
+            if (nodeToDelete == null)
+            {
+                return 0;
+            }
+
+            Delete(nodeToDelete);
+
+            _count--;
+
+            return 1;
+        }
+
+        /// <summary>
+        /// Adds all the nodes in the dictionary into <paramref name="list"/>.
+        /// </summary>
+        /// <returns>A list of all values sorted by Key Order</returns>
+        public List<V> AsList()
+        {
+            List<V> list = new List<V>();
+
+            AddToList(_root, list);
+
+            return list;
+        }
+
+        #endregion
+
+        #region Private Methods (BST)
+
+        /// <summary>
+        /// Adds all values that are children of or contained within <paramref name="node"/> into <paramref name="list"/>, in Key Order.
+        /// </summary>
+        /// <param name="node">The node to search for values within</param>
+        /// <param name="list">The list to add values to</param>
+        private void AddToList(IntervalTreeNode<K, V> node, List<V> list)
+        {
+            if (node == null)
+            {
+                return;
+            }
+
+            AddToList(node.Left, list);
+
+            list.Add(node.Value);
+
+            AddToList(node.Right, list);
+        }
+
+        /// <summary>
+        /// Retrieve the node reference whose key is <paramref name="key"/>, or null if no such node exists.
+        /// </summary>
+        /// <param name="key">Key of the node to get</param>
+        /// <exception cref="ArgumentNullException"><paramref name="key"/> is null</exception>
+        /// <returns>Node reference in the tree</returns>
+        private IntervalTreeNode<K, V> GetNode(K key)
+        {
+            if (key == null)
+            {
+                throw new ArgumentNullException(nameof(key));
+            }
+
+            IntervalTreeNode<K, V> node = _root;
+            while (node != null)
+            {
+                int cmp = key.CompareTo(node.Start);
+                if (cmp < 0)
+                {
+                    node = node.Left;
+                }
+                else if (cmp > 0)
+                {
+                    node = node.Right;
+                }
+                else
+                {
+                    return node;
+                }
+            }
+            return null;
+        }
+
+        /// <summary>
+        /// Retrieve all nodes that overlap the given start and end keys.
+        /// </summary>
+        /// <param name="start">Start of the range</param>
+        /// <param name="end">End of the range</param>
+        /// <param name="overlaps">Overlaps array to place results in</param>
+        /// <param name="overlapCount">Overlaps count to update</param>
+        private void GetNodes(IntervalTreeNode<K, V> node, K start, K end, ref IntervalTreeNode<K, V>[] overlaps, ref int overlapCount)
+        {
+            if (node == null || start.CompareTo(node.Max) >= 0)
+            {
+                return;
+            }
+
+            GetNodes(node.Left, start, end, ref overlaps, ref overlapCount);
+
+            bool endsOnRight = end.CompareTo(node.Start) > 0;
+            if (endsOnRight)
+            {
+                if (start.CompareTo(node.End) < 0)
+                {
+                    if (overlaps.Length >= overlapCount)
+                    {
+                        Array.Resize(ref overlaps, overlapCount + ArrayGrowthSize);
+                    }
+
+                    overlaps[overlapCount++] = node;
+                }
+
+                GetNodes(node.Right, start, end, ref overlaps, ref overlapCount);
+            }
+        }
+
+        /// <summary>
+        /// Propagate an increase in max value starting at the given node, heading up the tree.
+        /// This should only be called if the max increases - not for rebalancing or removals.
+        /// </summary>
+        /// <param name="node">The node to start propagating from</param>
+        private void PropagateIncrease(IntervalTreeNode<K, V> node)
+        {
+            K max = node.Max;
+            IntervalTreeNode<K, V> ptr = node;
+
+            while ((ptr = ptr.Parent) != null)
+            {
+                if (max.CompareTo(ptr.Max) > 0)
+                {
+                    ptr.Max = max;
+                }
+                else
+                {
+                    break;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Propagate recalculating max value starting at the given node, heading up the tree.
+        /// This fully recalculates the max value from all children when there is potential for it to decrease.
+        /// </summary>
+        /// <param name="node">The node to start propagating from</param>
+        private void PropagateFull(IntervalTreeNode<K, V> node)
+        {
+            IntervalTreeNode<K, V> ptr = node;
+
+            do
+            {
+                K max = ptr.End;
+
+                if (ptr.Left != null && ptr.Left.Max.CompareTo(max) > 0)
+                {
+                    max = ptr.Left.Max;
+                }
+
+                if (ptr.Right != null && ptr.Right.Max.CompareTo(max) > 0)
+                {
+                    max = ptr.Right.Max;
+                }
+
+                ptr.Max = max;
+            } while ((ptr = ptr.Parent) != null);
+        }
+
+        /// <summary>
+        /// Insertion Mechanism for the interval tree. Similar to a BST insert, with the start of the range as the key.
+        /// Iterates the tree starting from the root and inserts a new node where all children in the left subtree are less than <paramref name="start"/>, and all children in the right subtree are greater than <paramref name="start"/>.
+        /// Each node can contain multiple values, and has an end address which is the maximum of all those values.
+        /// Post insertion, the "max" value of the node and all parents are updated.
+        /// </summary>
+        /// <param name="start">Start of the range to insert</param>
+        /// <param name="end">End of the range to insert</param>
+        /// <param name="value">Value to insert</param>
+        /// <param name="updateFactoryCallback">Optional factory used to create a new value if <paramref name="start"/> is already on the tree</param>
+        /// <param name="outNode">Node that was inserted or modified</param>
+        /// <returns>True if <paramref name="start"/> was not yet on the tree, false otherwise</returns>
+        private bool BSTInsert(K start, K end, V value, Func<K, V, V> updateFactoryCallback, out IntervalTreeNode<K, V> outNode)
+        {
+            IntervalTreeNode<K, V> parent = null;
+            IntervalTreeNode<K, V> node = _root;
+
+            while (node != null)
+            {
+                parent = node;
+                int cmp = start.CompareTo(node.Start);
+                if (cmp < 0)
+                {
+                    node = node.Left;
+                }
+                else if (cmp > 0)
+                {
+                    node = node.Right;
+                }
+                else
+                {
+                    outNode = node;
+
+                    if (updateFactoryCallback != null)
+                    {
+                        // Replace
+                        node.Value = updateFactoryCallback(start, node.Value);
+
+                        int endCmp = end.CompareTo(node.End);
+
+                        if (endCmp > 0)
+                        {
+                            node.End = end;
+                            if (end.CompareTo(node.Max) > 0)
+                            {
+                                node.Max = end;
+                                PropagateIncrease(node);
+                                RestoreBalanceAfterInsertion(node);
+                            }
+                        }
+                        else if (endCmp < 0)
+                        {
+                            node.End = end;
+                            PropagateFull(node);
+                        }
+                    }
+
+                    return false;
+                }
+            }
+            IntervalTreeNode<K, V> newNode = new IntervalTreeNode<K, V>(start, end, value, parent);
+            if (newNode.Parent == null)
+            {
+                _root = newNode;
+            }
+            else if (start.CompareTo(parent.Start) < 0)
+            {
+                parent.Left = newNode;
+            }
+            else
+            {
+                parent.Right = newNode;
+            }
+
+            PropagateIncrease(newNode);
+            _count++;
+            RestoreBalanceAfterInsertion(newNode);
+            outNode = newNode;
+            return true;
+        }
+
+        /// <summary>
+        /// Removes the value from the dictionary after searching for it with <paramref name="key">.
+        /// </summary>
+        /// <param name="key">Tree node to be removed</param>
+        private void Delete(IntervalTreeNode<K, V> nodeToDelete)
+        {
+            IntervalTreeNode<K, V> replacementNode;
+
+            if (LeftOf(nodeToDelete) == null || RightOf(nodeToDelete) == null)
+            {
+                replacementNode = nodeToDelete;
+            }
+            else
+            {
+                replacementNode = PredecessorOf(nodeToDelete);
+            }
+
+            IntervalTreeNode<K, V> tmp = LeftOf(replacementNode) ?? RightOf(replacementNode);
+
+            if (tmp != null)
+            {
+                tmp.Parent = ParentOf(replacementNode);
+            }
+
+            if (ParentOf(replacementNode) == null)
+            {
+                _root = tmp;
+            }
+            else if (replacementNode == LeftOf(ParentOf(replacementNode)))
+            {
+                ParentOf(replacementNode).Left = tmp;
+            }
+            else
+            {
+                ParentOf(replacementNode).Right = tmp;
+            }
+
+            if (replacementNode != nodeToDelete)
+            {
+                nodeToDelete.Start = replacementNode.Start;
+                nodeToDelete.Value = replacementNode.Value;
+                nodeToDelete.End = replacementNode.End;
+                nodeToDelete.Max = replacementNode.Max;
+            }
+
+            PropagateFull(replacementNode);
+
+            if (tmp != null && ColorOf(replacementNode) == Black)
+            {
+                RestoreBalanceAfterRemoval(tmp);
+            }
+        }
+
+        /// <summary>
+        /// Returns the node with the largest key where <paramref name="node"/> is considered the root node.
+        /// </summary>
+        /// <param name="node">Root Node</param>
+        /// <returns>Node with the maximum key in the tree of <paramref name="node"/></returns>
+        private static IntervalTreeNode<K, V> Maximum(IntervalTreeNode<K, V> node)
+        {
+            IntervalTreeNode<K, V> tmp = node;
+            while (tmp.Right != null)
+            {
+                tmp = tmp.Right;
+            }
+
+            return tmp;
+        }
+
+        /// <summary>
+        /// Finds the node whose key is immediately less than <paramref name="node"/>.
+        /// </summary>
+        /// <param name="node">Node to find the predecessor of</param>
+        /// <returns>Predecessor of <paramref name="node"/></returns>
+        private static IntervalTreeNode<K, V> PredecessorOf(IntervalTreeNode<K, V> node)
+        {
+            if (node.Left != null)
+            {
+                return Maximum(node.Left);
+            }
+            IntervalTreeNode<K, V> parent = node.Parent;
+            while (parent != null && node == parent.Left)
+            {
+                node = parent;
+                parent = parent.Parent;
+            }
+            return parent;
+        }
+
+        #endregion
+
+        #region Private Methods (RBL)
+
+        private void RestoreBalanceAfterRemoval(IntervalTreeNode<K, V> balanceNode)
+        {
+            IntervalTreeNode<K, V> ptr = balanceNode;
+
+            while (ptr != _root && ColorOf(ptr) == Black)
+            {
+                if (ptr == LeftOf(ParentOf(ptr)))
+                {
+                    IntervalTreeNode<K, V> sibling = RightOf(ParentOf(ptr));
+
+                    if (ColorOf(sibling) == Red)
+                    {
+                        SetColor(sibling, Black);
+                        SetColor(ParentOf(ptr), Red);
+                        RotateLeft(ParentOf(ptr));
+                        sibling = RightOf(ParentOf(ptr));
+                    }
+                    if (ColorOf(LeftOf(sibling)) == Black && ColorOf(RightOf(sibling)) == Black)
+                    {
+                        SetColor(sibling, Red);
+                        ptr = ParentOf(ptr);
+                    }
+                    else
+                    {
+                        if (ColorOf(RightOf(sibling)) == Black)
+                        {
+                            SetColor(LeftOf(sibling), Black);
+                            SetColor(sibling, Red);
+                            RotateRight(sibling);
+                            sibling = RightOf(ParentOf(ptr));
+                        }
+                        SetColor(sibling, ColorOf(ParentOf(ptr)));
+                        SetColor(ParentOf(ptr), Black);
+                        SetColor(RightOf(sibling), Black);
+                        RotateLeft(ParentOf(ptr));
+                        ptr = _root;
+                    }
+                }
+                else
+                {
+                    IntervalTreeNode<K, V> sibling = LeftOf(ParentOf(ptr));
+
+                    if (ColorOf(sibling) == Red)
+                    {
+                        SetColor(sibling, Black);
+                        SetColor(ParentOf(ptr), Red);
+                        RotateRight(ParentOf(ptr));
+                        sibling = LeftOf(ParentOf(ptr));
+                    }
+                    if (ColorOf(RightOf(sibling)) == Black && ColorOf(LeftOf(sibling)) == Black)
+                    {
+                        SetColor(sibling, Red);
+                        ptr = ParentOf(ptr);
+                    }
+                    else
+                    {
+                        if (ColorOf(LeftOf(sibling)) == Black)
+                        {
+                            SetColor(RightOf(sibling), Black);
+                            SetColor(sibling, Red);
+                            RotateLeft(sibling);
+                            sibling = LeftOf(ParentOf(ptr));
+                        }
+                        SetColor(sibling, ColorOf(ParentOf(ptr)));
+                        SetColor(ParentOf(ptr), Black);
+                        SetColor(LeftOf(sibling), Black);
+                        RotateRight(ParentOf(ptr));
+                        ptr = _root;
+                    }
+                }
+            }
+            SetColor(ptr, Black);
+        }
+
+        private void RestoreBalanceAfterInsertion(IntervalTreeNode<K, V> balanceNode)
+        {
+            SetColor(balanceNode, Red);
+            while (balanceNode != null && balanceNode != _root && ColorOf(ParentOf(balanceNode)) == Red)
+            {
+                if (ParentOf(balanceNode) == LeftOf(ParentOf(ParentOf(balanceNode))))
+                {
+                    IntervalTreeNode<K, V> sibling = RightOf(ParentOf(ParentOf(balanceNode)));
+
+                    if (ColorOf(sibling) == Red)
+                    {
+                        SetColor(ParentOf(balanceNode), Black);
+                        SetColor(sibling, Black);
+                        SetColor(ParentOf(ParentOf(balanceNode)), Red);
+                        balanceNode = ParentOf(ParentOf(balanceNode));
+                    }
+                    else
+                    {
+                        if (balanceNode == RightOf(ParentOf(balanceNode)))
+                        {
+                            balanceNode = ParentOf(balanceNode);
+                            RotateLeft(balanceNode);
+                        }
+                        SetColor(ParentOf(balanceNode), Black);
+                        SetColor(ParentOf(ParentOf(balanceNode)), Red);
+                        RotateRight(ParentOf(ParentOf(balanceNode)));
+                    }
+                }
+                else
+                {
+                    IntervalTreeNode<K, V> sibling = LeftOf(ParentOf(ParentOf(balanceNode)));
+
+                    if (ColorOf(sibling) == Red)
+                    {
+                        SetColor(ParentOf(balanceNode), Black);
+                        SetColor(sibling, Black);
+                        SetColor(ParentOf(ParentOf(balanceNode)), Red);
+                        balanceNode = ParentOf(ParentOf(balanceNode));
+                    }
+                    else
+                    {
+                        if (balanceNode == LeftOf(ParentOf(balanceNode)))
+                        {
+                            balanceNode = ParentOf(balanceNode);
+                            RotateRight(balanceNode);
+                        }
+                        SetColor(ParentOf(balanceNode), Black);
+                        SetColor(ParentOf(ParentOf(balanceNode)), Red);
+                        RotateLeft(ParentOf(ParentOf(balanceNode)));
+                    }
+                }
+            }
+            SetColor(_root, Black);
+        }
+
+        private void RotateLeft(IntervalTreeNode<K, V> node)
+        {
+            if (node != null)
+            {
+                IntervalTreeNode<K, V> right = RightOf(node);
+                node.Right = LeftOf(right);
+                if (node.Right != null)
+                {
+                    node.Right.Parent = node;
+                }
+                IntervalTreeNode<K, V> nodeParent = ParentOf(node);
+                right.Parent = nodeParent;
+                if (nodeParent == null)
+                {
+                    _root = right;
+                }
+                else if (node == LeftOf(nodeParent))
+                {
+                    nodeParent.Left = right;
+                }
+                else
+                {
+                    nodeParent.Right = right;
+                }
+                right.Left = node;
+                node.Parent = right;
+
+                PropagateFull(node);
+            }
+        }
+
+        private void RotateRight(IntervalTreeNode<K, V> node)
+        {
+            if (node != null)
+            {
+                IntervalTreeNode<K, V> left = LeftOf(node);
+                node.Left = RightOf(left);
+                if (node.Left != null)
+                {
+                    node.Left.Parent = node;
+                }
+                IntervalTreeNode<K, V> nodeParent = ParentOf(node);
+                left.Parent = nodeParent;
+                if (nodeParent == null)
+                {
+                    _root = left;
+                }
+                else if (node == RightOf(nodeParent))
+                {
+                    nodeParent.Right = left;
+                }
+                else
+                {
+                    nodeParent.Left = left;
+                }
+                left.Right = node;
+                node.Parent = left;
+
+                PropagateFull(node);
+            }
+        }
+
+        #endregion
+
+        #region Safety-Methods
+
+        // These methods save memory by allowing us to forego sentinel nil nodes, as well as serve as protection against NullReferenceExceptions.
+
+        /// <summary>
+        /// Returns the color of <paramref name="node"/>, or Black if it is null.
+        /// </summary>
+        /// <param name="node">Node</param>
+        /// <returns>The boolean color of <paramref name="node"/>, or black if null</returns>
+        private static bool ColorOf(IntervalTreeNode<K, V> node)
+        {
+            return node == null || node.Color;
+        }
+
+        /// <summary>
+        /// Sets the color of <paramref name="node"/> node to <paramref name="color"/>.
+        /// <br></br>
+        /// This method does nothing if <paramref name="node"/> is null.
+        /// </summary>
+        /// <param name="node">Node to set the color of</param>
+        /// <param name="color">Color (Boolean)</param>
+        private static void SetColor(IntervalTreeNode<K, V> node, bool color)
+        {
+            if (node != null)
+            {
+                node.Color = color;
+            }
+        }
+
+        /// <summary>
+        /// This method returns the left node of <paramref name="node"/>, or null if <paramref name="node"/> is null.
+        /// </summary>
+        /// <param name="node">Node to retrieve the left child from</param>
+        /// <returns>Left child of <paramref name="node"/></returns>
+        private static IntervalTreeNode<K, V> LeftOf(IntervalTreeNode<K, V> node)
+        {
+            return node?.Left;
+        }
+
+        /// <summary>
+        /// This method returns the right node of <paramref name="node"/>, or null if <paramref name="node"/> is null.
+        /// </summary>
+        /// <param name="node">Node to retrieve the right child from</param>
+        /// <returns>Right child of <paramref name="node"/></returns>
+        private static IntervalTreeNode<K, V> RightOf(IntervalTreeNode<K, V> node)
+        {
+            return node?.Right;
+        }
+
+        /// <summary>
+        /// Returns the parent node of <paramref name="node"/>, or null if <paramref name="node"/> is null.
+        /// </summary>
+        /// <param name="node">Node to retrieve the parent from</param>
+        /// <returns>Parent of <paramref name="node"/></returns>
+        private static IntervalTreeNode<K, V> ParentOf(IntervalTreeNode<K, V> node)
+        {
+            return node?.Parent;
+        }
+
+        #endregion
+
+        public bool ContainsKey(K key)
+        {
+            return GetNode(key) != null;
+        }
+
+        public void Clear()
+        {
+            _root = null;
+            _count = 0;
+        }
+    }
+
+    /// <summary>
+    /// Represents a node in the IntervalTree which contains start and end keys of type K, and a value of generic type V.
+    /// </summary>
+    /// <typeparam name="K">Key type of the node</typeparam>
+    /// <typeparam name="V">Value type of the node</typeparam>
+    class IntervalTreeNode<K, V>
+    {
+        public bool Color = true;
+        public IntervalTreeNode<K, V> Left = null;
+        public IntervalTreeNode<K, V> Right = null;
+        public IntervalTreeNode<K, V> Parent = null;
+
+        /// <summary>
+        /// The start of the range.
+        /// </summary>
+        public K Start;
+
+        /// <summary>
+        /// The end of the range.
+        /// </summary>
+        public K End;
+
+        /// <summary>
+        /// The maximum end value of this node and all its children.
+        /// </summary>
+        public K Max;
+
+        /// <summary>
+        /// Value stored on this node.
+        /// </summary>
+        public V Value;
+
+        public IntervalTreeNode(K start, K end, V value, IntervalTreeNode<K, V> parent)
+        {
+            Start = start;
+            End = end;
+            Max = end;
+            Value = value;
+            Parent = parent;
+        }
+    }
+}

Ryujinx.Memory/WindowsShared/PlaceholderList.cs

@@ -1,293 +0,0 @@
-using Ryujinx.Memory.Range;
-using System;
-using System.Diagnostics;
-
-namespace Ryujinx.Memory.WindowsShared
-{
-    /// <summary>
-    /// A specialized list used for keeping track of Windows 10's memory placeholders.
-    /// This is used to make splitting a large placeholder into equally small
-    /// granular chunks much easier, while avoiding slowdown due to a large number of
-    /// placeholders by coalescing adjacent granular placeholders after they are unused.
-    /// </summary>
-    class PlaceholderList
-    {
-        private class PlaceholderBlock : IRange
-        {
-            public ulong Address { get; }
-            public ulong Size { get; private set; }
-            public ulong EndAddress { get; private set; }
-            public bool IsGranular { get; set; }
-
-            public PlaceholderBlock(ulong id, ulong size, bool isGranular)
-            {
-                Address = id;
-                Size = size;
-                EndAddress = id + size;
-                IsGranular = isGranular;
-            }
-
-            public bool OverlapsWith(ulong address, ulong size)
-            {
-                return Address < address + size && address < EndAddress;
-            }
-
-            public void ExtendTo(ulong end, RangeList<PlaceholderBlock> list)
-            {
-                EndAddress = end;
-                Size = end - Address;
-
-                list.UpdateEndAddress(this);
-            }
-        }
-
-        private RangeList<PlaceholderBlock> _placeholders;
-        private PlaceholderBlock[] _foundBlocks = new PlaceholderBlock[32];
-
-        /// <summary>
-        /// Create a new list to manage placeholders.
-        /// Note that a size is measured in granular placeholders.
-        /// If the placeholder granularity is 65536 bytes, then a 65536 region will be covered by 1 placeholder granularity.
-        /// </summary>
-        /// <param name="size">Size measured in granular placeholders</param>
-        public PlaceholderList(ulong size)
-        {
-            _placeholders = new RangeList<PlaceholderBlock>();
-
-            _placeholders.Add(new PlaceholderBlock(0, size, false));
-        }
-
-        /// <summary>
-        /// Ensure that the given range of placeholders is granular.
-        /// </summary>
-        /// <param name="id">Start of the range, measured in granular placeholders</param>
-        /// <param name="size">Size of the range, measured in granular placeholders</param>
-        /// <param name="splitPlaceholderCallback">Callback function to run when splitting placeholders, calls with (start, middle)</param>
-        public void EnsurePlaceholders(ulong id, ulong size, Action<ulong, ulong> splitPlaceholderCallback)
-        {
-            // Search 1 before and after the placeholders, as we may need to expand/join granular regions surrounding the requested area.
-
-            ulong endId = id + size;
-            ulong searchStartId = id == 0 ? 0 : (id - 1);
-            int blockCount = _placeholders.FindOverlapsNonOverlapping(searchStartId, (endId - searchStartId) + 1, ref _foundBlocks);
-
-            PlaceholderBlock first = _foundBlocks[0];
-            PlaceholderBlock last = _foundBlocks[blockCount - 1];
-            bool overlapStart = first.EndAddress >= id && id != 0;
-            bool overlapEnd = last.Address <= endId;
-
-            for (int i = 0; i < blockCount; i++)
-            {
-                // Go through all non-granular blocks in the range and create placeholders.
-                PlaceholderBlock block = _foundBlocks[i];
-
-                if (block.Address <= id && block.EndAddress >= endId && block.IsGranular)
-                {
-                    return; // The region we're searching for is already granular.
-                }
-
-                if (!block.IsGranular)
-                {
-                    ulong placeholderStart = Math.Max(block.Address, id);
-                    ulong placeholderEnd = Math.Min(block.EndAddress - 1, endId);
-
-                    if (placeholderStart != block.Address && placeholderStart != block.EndAddress)
-                    {
-                        splitPlaceholderCallback(block.Address, placeholderStart - block.Address);
-                    }
-
-                    for (ulong j = placeholderStart; j < placeholderEnd; j++)
-                    {
-                        splitPlaceholderCallback(j, 1);
-                    }
-                }
-
-                if (!((block == first && overlapStart) || (block == last && overlapEnd)))
-                {
-                    // Remove blocks that will be replaced
-                    _placeholders.Remove(block);
-                }
-            }
-
-            if (overlapEnd)
-            {
-                if (!(first == last && overlapStart))
-                {
-                    _placeholders.Remove(last);
-                }
-
-                if (last.IsGranular)
-                {
-                    endId = last.EndAddress;
-                }
-                else if (last.EndAddress != endId)
-                {
-                    _placeholders.Add(new PlaceholderBlock(endId, last.EndAddress - endId, false));
-                }
-            }
-
-            if (overlapStart && first.IsGranular)
-            {
-                first.ExtendTo(endId, _placeholders);
-            }
-            else
-            {
-                if (overlapStart)
-                {
-                    first.ExtendTo(id, _placeholders);
-                }
-
-                _placeholders.Add(new PlaceholderBlock(id, endId - id, true));
-            }
-
-            ValidateList();
-        }
-
-        /// <summary>
-        /// Coalesces placeholders in a given region, as they are not being used.
-        /// This assumes that the region only contains placeholders - all views and allocations must have been replaced with placeholders.
-        /// </summary>
-        /// <param name="id">Start of the range, measured in granular placeholders</param>
-        /// <param name="size">Size of the range, measured in granular placeholders</param>
-        /// <param name="coalescePlaceholderCallback">Callback function to run when coalescing two placeholders, calls with (start, end)</param>
-        public void RemovePlaceholders(ulong id, ulong size, Action<ulong, ulong> coalescePlaceholderCallback)
-        {
-            ulong endId = id + size;
-            int blockCount = _placeholders.FindOverlapsNonOverlapping(id, size, ref _foundBlocks);
-
-            PlaceholderBlock first = _foundBlocks[0];
-            PlaceholderBlock last = _foundBlocks[blockCount - 1];
-
-            // All granular blocks must have non-granular blocks surrounding them, unless they start at 0.
-            // We must extend the non-granular blocks into the granular ones. This does mean that we need to search twice.
-
-            if (first.IsGranular || last.IsGranular)
-            {
-                ulong surroundStart = Math.Max(0, (first.IsGranular && first.Address != 0) ? first.Address - 1 : id);
-                blockCount = _placeholders.FindOverlapsNonOverlapping(
-                    surroundStart,
-                    (last.IsGranular ? last.EndAddress + 1 : endId) - surroundStart,
-                    ref _foundBlocks);
-
-                first = _foundBlocks[0];
-                last = _foundBlocks[blockCount - 1];
-            }
-
-            if (first == last)
-            {
-                return; // Already coalesced.
-            }
-
-            PlaceholderBlock extendBlock = id == 0 ? null : first;
-            bool newBlock = false;
-            for (int i = extendBlock == null ? 0 : 1; i < blockCount; i++)
-            {
-                // Go through all granular blocks in the range and extend placeholders.
-                PlaceholderBlock block = _foundBlocks[i];
-
-                ulong blockEnd = block.EndAddress;
-                ulong extendFrom;
-                ulong extent = Math.Min(blockEnd, endId);
-
-                if (block.Address < id && blockEnd > id)
-                {
-                    block.ExtendTo(id, _placeholders);
-                    extendBlock = null;
-                }
-                else
-                {
-                    _placeholders.Remove(block);
-                }
-
-                if (extendBlock == null)
-                {
-                    extendFrom = id;
-                    extendBlock = new PlaceholderBlock(id, extent - id, false);
-                    _placeholders.Add(extendBlock);
-
-                    if (blockEnd > extent)
-                    {
-                        _placeholders.Add(new PlaceholderBlock(extent, blockEnd - extent, true));
-
-                        // Skip the next non-granular block, and extend from that into the granular block afterwards.
-                        // (assuming that one is still in the requested range)
-
-                        if (i + 1 < blockCount)
-                        {
-                            extendBlock = _foundBlocks[i + 1];
-                        }
-
-                        i++;
-                    }
-
-                    newBlock = true;
-                }
-                else
-                {
-                    extendFrom = extendBlock.Address;
-                    extendBlock.ExtendTo(block.IsGranular ? extent : block.EndAddress, _placeholders);
-                }
-
-                if (block.IsGranular)
-                {
-                    ulong placeholderStart = Math.Max(block.Address, id);
-                    ulong placeholderEnd = extent;
-
-                    if (newBlock)
-                    {
-                        placeholderStart++;
-                        newBlock = false;
-                    }
-
-                    for (ulong j = placeholderStart; j < placeholderEnd; j++)
-                    {
-                        coalescePlaceholderCallback(extendFrom, (j + 1) - extendFrom);
-                    }
-
-                    if (extent < block.EndAddress)
-                    {
-                        _placeholders.Add(new PlaceholderBlock(placeholderEnd, block.EndAddress - placeholderEnd, true));
-                        ValidateList();
-                        return;
-                    }
-                }
-                else
-                {
-                    coalescePlaceholderCallback(extendFrom, block.EndAddress - extendFrom);
-                }
-            }
-
-            ValidateList();
-        }
-
-        /// <summary>
-        /// Ensure that the placeholder list is valid.
-        /// A valid list should not have any gaps between the placeholders,
-        /// and there may be no placehonders with the same IsGranular value next to each other.
-        /// </summary>
-        [Conditional("DEBUG")]
-        private void ValidateList()
-        {
-            bool isGranular = false;
-            bool first = true;
-            ulong lastAddress = 0;
-
-            foreach (var placeholder in _placeholders)
-            {
-                if (placeholder.Address != lastAddress)
-                {
-                    throw new InvalidOperationException("Gap in placeholder list.");
-                }
-
-                if (isGranular == placeholder.IsGranular && !first)
-                {
-                    throw new InvalidOperationException("Placeholder list not alternating.");
-                }
-
-                first = false;
-                isGranular = placeholder.IsGranular;
-                lastAddress = placeholder.EndAddress;
-            }
-        }
-    }
-}

Ryujinx.Memory/WindowsShared/PlaceholderManager.cs

@@ -0,0 +1,633 @@
+using System;
+using System.Diagnostics;
+using System.Threading;
+
+namespace Ryujinx.Memory.WindowsShared
+{
+    /// <summary>
+    /// Windows memory placeholder manager.
+    /// </summary>
+    class PlaceholderManager
+    {
+        private const ulong MinimumPageSize = 0x1000;
+
+        [ThreadStatic]
+        private static int _threadLocalPartialUnmapsCount;
+
+        private readonly IntervalTree<ulong, ulong> _mappings;
+        private readonly IntervalTree<ulong, MemoryPermission> _protections;
+        private readonly ReaderWriterLock _partialUnmapLock;
+        private int _partialUnmapsCount;
+
+        /// <summary>
+        /// Creates a new instance of the Windows memory placeholder manager.
+        /// </summary>
+        public PlaceholderManager()
+        {
+            _mappings = new IntervalTree<ulong, ulong>();
+            _protections = new IntervalTree<ulong, MemoryPermission>();
+            _partialUnmapLock = new ReaderWriterLock();
+        }
+
+        /// <summary>
+        /// Reserves a range of the address space to be later mapped as shared memory views.
+        /// </summary>
+        /// <param name="address">Start address of the region to reserve</param>
+        /// <param name="size">Size in bytes of the region to reserve</param>
+        public void ReserveRange(ulong address, ulong size)
+        {
+            lock (_mappings)
+            {
+                _mappings.Add(address, address + size, ulong.MaxValue);
+            }
+        }
+
+        /// <summary>
+        /// Maps a shared memory view on a previously reserved memory region.
+        /// </summary>
+        /// <param name="sharedMemory">Shared memory that will be the backing storage for the view</param>
+        /// <param name="srcOffset">Offset in the shared memory to map</param>
+        /// <param name="location">Address to map the view into</param>
+        /// <param name="size">Size of the view in bytes</param>
+        public void MapView(IntPtr sharedMemory, ulong srcOffset, IntPtr location, IntPtr size)
+        {
+            _partialUnmapLock.AcquireReaderLock(Timeout.Infinite);
+
+            try
+            {
+                UnmapViewInternal(sharedMemory, location, size);
+                MapViewInternal(sharedMemory, srcOffset, location, size);
+            }
+            finally
+            {
+                _partialUnmapLock.ReleaseReaderLock();
+            }
+        }
+
+        /// <summary>
+        /// Maps a shared memory view on a previously reserved memory region.
+        /// </summary>
+        /// <param name="sharedMemory">Shared memory that will be the backing storage for the view</param>
+        /// <param name="srcOffset">Offset in the shared memory to map</param>
+        /// <param name="location">Address to map the view into</param>
+        /// <param name="size">Size of the view in bytes</param>
+        /// <exception cref="WindowsApiException">Thrown when the Windows API returns an error mapping the memory</exception>
+        private void MapViewInternal(IntPtr sharedMemory, ulong srcOffset, IntPtr location, IntPtr size)
+        {
+            SplitForMap((ulong)location, (ulong)size, srcOffset);
+
+            var ptr = WindowsApi.MapViewOfFile3(
+                sharedMemory,
+                WindowsApi.CurrentProcessHandle,
+                location,
+                srcOffset,
+                size,
+                0x4000,
+                MemoryProtection.ReadWrite,
+                IntPtr.Zero,
+                0);
+
+            if (ptr == IntPtr.Zero)
+            {
+                throw new WindowsApiException("MapViewOfFile3");
+            }
+        }
+
+        /// <summary>
+        /// Splits a larger placeholder, slicing at the start and end address, for a new memory mapping.
+        /// </summary>
+        /// <param name="address">Address to split</param>
+        /// <param name="size">Size of the new region</param>
+        /// <param name="backingOffset">Offset in the shared memory that will be mapped</param>
+        private void SplitForMap(ulong address, ulong size, ulong backingOffset)
+        {
+            ulong endAddress = address + size;
+
+            var overlaps = Array.Empty<IntervalTreeNode<ulong, ulong>>();
+
+            lock (_mappings)
+            {
+                int count = _mappings.Get(address, endAddress, ref overlaps);
+
+                Debug.Assert(count == 1);
+                Debug.Assert(!IsMapped(overlaps[0].Value));
+
+                var overlap = overlaps[0];
+
+                // Tree operations might modify the node start/end values, so save a copy before we modify the tree.
+                ulong overlapStart = overlap.Start;
+                ulong overlapEnd = overlap.End;
+                ulong overlapValue = overlap.Value;
+
+                _mappings.Remove(overlap);
+
+                bool overlapStartsBefore = overlapStart < address;
+                bool overlapEndsAfter = overlapEnd > endAddress;
+
+                if (overlapStartsBefore && overlapEndsAfter)
+                {
+                    CheckFreeResult(WindowsApi.VirtualFree(
+                        (IntPtr)address,
+                        (IntPtr)size,
+                        AllocationType.Release | AllocationType.PreservePlaceholder));
+
+                    _mappings.Add(overlapStart, address, overlapValue);
+                    _mappings.Add(endAddress, overlapEnd, AddBackingOffset(overlapValue, endAddress - overlapStart));
+                }
+                else if (overlapStartsBefore)
+                {
+                    ulong overlappedSize = overlapEnd - address;
+
+                    CheckFreeResult(WindowsApi.VirtualFree(
+                        (IntPtr)address,
+                        (IntPtr)overlappedSize,
+                        AllocationType.Release | AllocationType.PreservePlaceholder));
+
+                    _mappings.Add(overlapStart, address, overlapValue);
+                }
+                else if (overlapEndsAfter)
+                {
+                    ulong overlappedSize = endAddress - overlapStart;
+
+                    CheckFreeResult(WindowsApi.VirtualFree(
+                        (IntPtr)overlapStart,
+                        (IntPtr)overlappedSize,
+                        AllocationType.Release | AllocationType.PreservePlaceholder));
+
+                    _mappings.Add(endAddress, overlapEnd, AddBackingOffset(overlapValue, overlappedSize));
+                }
+
+                _mappings.Add(address, endAddress, backingOffset);
+            }
+        }
+
+        /// <summary>
+        /// Unmaps a view that has been previously mapped with <see cref="MapView"/>.
+        /// </summary>
+        /// <remarks>
+        /// For "partial unmaps" (when not the entire mapped range is being unmapped), it might be
+        /// necessary to unmap the whole range and then remap the sub-ranges that should remain mapped.
+        /// </remarks>
+        /// <param name="sharedMemory">Shared memory that the view being unmapped belongs to</param>
+        /// <param name="location">Address to unmap</param>
+        /// <param name="size">Size of the region to unmap in bytes</param>
+        public void UnmapView(IntPtr sharedMemory, IntPtr location, IntPtr size)
+        {
+            _partialUnmapLock.AcquireReaderLock(Timeout.Infinite);
+
+            try
+            {
+                UnmapViewInternal(sharedMemory, location, size);
+            }
+            finally
+            {
+                _partialUnmapLock.ReleaseReaderLock();
+            }
+        }
+
+        /// <summary>
+        /// Unmaps a view that has been previously mapped with <see cref="MapView"/>.
+        /// </summary>
+        /// <remarks>
+        /// For "partial unmaps" (when not the entire mapped range is being unmapped), it might be
+        /// necessary to unmap the whole range and then remap the sub-ranges that should remain mapped.
+        /// </remarks>
+        /// <param name="sharedMemory">Shared memory that the view being unmapped belongs to</param>
+        /// <param name="location">Address to unmap</param>
+        /// <param name="size">Size of the region to unmap in bytes</param>
+        /// <exception cref="WindowsApiException">Thrown when the Windows API returns an error unmapping or remapping the memory</exception>
+        private void UnmapViewInternal(IntPtr sharedMemory, IntPtr location, IntPtr size)
+        {
+            ulong startAddress = (ulong)location;
+            ulong unmapSize = (ulong)size;
+            ulong endAddress = startAddress + unmapSize;
+
+            var overlaps = Array.Empty<IntervalTreeNode<ulong, ulong>>();
+            int count = 0;
+
+            lock (_mappings)
+            {
+                count = _mappings.Get(startAddress, endAddress, ref overlaps);
+            }
+
+            for (int index = 0; index < count; index++)
+            {
+                var overlap = overlaps[index];
+
+                if (IsMapped(overlap.Value))
+                {
+                    if (!WindowsApi.UnmapViewOfFile2(WindowsApi.CurrentProcessHandle, (IntPtr)overlap.Start, 2))
+                    {
+                        throw new WindowsApiException("UnmapViewOfFile2");
+                    }
+
+                    // Tree operations might modify the node start/end values, so save a copy before we modify the tree.
+                    ulong overlapStart = overlap.Start;
+                    ulong overlapEnd = overlap.End;
+                    ulong overlapValue = overlap.Value;
+
+                    _mappings.Remove(overlap);
+                    _mappings.Add(overlapStart, overlapEnd, ulong.MaxValue);
+
+                    bool overlapStartsBefore = overlapStart < startAddress;
+                    bool overlapEndsAfter = overlapEnd > endAddress;
+
+                    if (overlapStartsBefore || overlapEndsAfter)
+                    {
+                        // If the overlap extends beyond the region we are unmapping,
+                        // then we need to re-map the regions that are supposed to remain mapped.
+                        // This is necessary because Windows does not support partial view unmaps.
+                        // That is, you can only fully unmap a view that was previously mapped, you can't just unmap a chunck of it.
+
+                        LockCookie lockCookie = _partialUnmapLock.UpgradeToWriterLock(Timeout.Infinite);
+
+                        _partialUnmapsCount++;
+
+                        if (overlapStartsBefore)
+                        {
+                            ulong remapSize = startAddress - overlapStart;
+
+                            MapViewInternal(sharedMemory, overlapValue, (IntPtr)overlapStart, (IntPtr)remapSize);
+                            RestoreRangeProtection(overlapStart, remapSize);
+                        }
+
+                        if (overlapEndsAfter)
+                        {
+                            ulong overlappedSize = endAddress - overlapStart;
+                            ulong remapBackingOffset = overlapValue + overlappedSize;
+                            ulong remapAddress = overlapStart + overlappedSize;
+                            ulong remapSize = overlapEnd - endAddress;
+
+                            MapViewInternal(sharedMemory, remapBackingOffset, (IntPtr)remapAddress, (IntPtr)remapSize);
+                            RestoreRangeProtection(remapAddress, remapSize);
+                        }
+
+                        _partialUnmapLock.DowngradeFromWriterLock(ref lockCookie);
+                    }
+                }
+            }
+
+            CoalesceForUnmap(startAddress, unmapSize);
+            RemoveProtection(startAddress, unmapSize);
+        }
+
+        /// <summary>
+        /// Coalesces adjacent placeholders after unmap.
+        /// </summary>
+        /// <param name="address">Address of the region that was unmapped</param>
+        /// <param name="size">Size of the region that was unmapped in bytes</param>
+        private void CoalesceForUnmap(ulong address, ulong size)
+        {
+            ulong endAddress = address + size;
+            var overlaps = Array.Empty<IntervalTreeNode<ulong, ulong>>();
+            int unmappedCount = 0;
+
+            lock (_mappings)
+            {
+                int count = _mappings.Get(address - MinimumPageSize, endAddress + MinimumPageSize, ref overlaps);
+                if (count < 2)
+                {
+                    // Nothing to coalesce if we only have 1 or no overlaps.
+                    return;
+                }
+
+                for (int index = 0; index < count; index++)
+                {
+                    var overlap = overlaps[index];
+
+                    if (!IsMapped(overlap.Value))
+                    {
+                        if (address > overlap.Start)
+                        {
+                            address = overlap.Start;
+                        }
+
+                        if (endAddress < overlap.End)
+                        {
+                            endAddress = overlap.End;
+                        }
+
+                        _mappings.Remove(overlap);
+
+                        unmappedCount++;
+                    }
+                }
+
+                _mappings.Add(address, endAddress, ulong.MaxValue);
+            }
+
+            if (unmappedCount > 1)
+            {
+                size = endAddress - address;
+
+                CheckFreeResult(WindowsApi.VirtualFree(
+                    (IntPtr)address,
+                    (IntPtr)size,
+                    AllocationType.Release | AllocationType.CoalescePlaceholders));
+            }
+        }
+
+        /// <summary>
+        /// Reprotects a region of memory that has been mapped.
+        /// </summary>
+        /// <param name="address">Address of the region to reprotect</param>
+        /// <param name="size">Size of the region to reprotect in bytes</param>
+        /// <param name="permission">New permissions</param>
+        /// <returns>True if the reprotection was successful, false otherwise</returns>
+        public bool ReprotectView(IntPtr address, IntPtr size, MemoryPermission permission)
+        {
+            _partialUnmapLock.AcquireReaderLock(Timeout.Infinite);
+
+            try
+            {
+                return ReprotectViewInternal(address, size, permission, false);
+            }
+            finally
+            {
+                _partialUnmapLock.ReleaseReaderLock();
+            }
+        }
+
+        /// <summary>
+        /// Reprotects a region of memory that has been mapped.
+        /// </summary>
+        /// <param name="address">Address of the region to reprotect</param>
+        /// <param name="size">Size of the region to reprotect in bytes</param>
+        /// <param name="permission">New permissions</param>
+        /// <param name="throwOnError">Throw an exception instead of returning an error if the operation fails</param>
+        /// <returns>True if the reprotection was successful or if <paramref name="throwOnError"/> is true, false otherwise</returns>
+        /// <exception cref="WindowsApiException">If <paramref name="throwOnError"/> is true, it is thrown when the Windows API returns an error reprotecting the memory</exception>
+        private bool ReprotectViewInternal(IntPtr address, IntPtr size, MemoryPermission permission, bool throwOnError)
+        {
+            ulong reprotectAddress = (ulong)address;
+            ulong reprotectSize = (ulong)size;
+            ulong endAddress = reprotectAddress + reprotectSize;
+
+            var overlaps = Array.Empty<IntervalTreeNode<ulong, ulong>>();
+            int count = 0;
+
+            lock (_mappings)
+            {
+                count = _mappings.Get(reprotectAddress, endAddress, ref overlaps);
+            }
+
+            bool success = true;
+
+            for (int index = 0; index < count; index++)
+            {
+                var overlap = overlaps[index];
+
+                ulong mappedAddress = overlap.Start;
+                ulong mappedSize = overlap.End - overlap.Start;
+
+                if (mappedAddress < reprotectAddress)
+                {
+                    ulong delta = reprotectAddress - mappedAddress;
+                    mappedAddress = reprotectAddress;
+                    mappedSize -= delta;
+                }
+
+                ulong mappedEndAddress = mappedAddress + mappedSize;
+
+                if (mappedEndAddress > endAddress)
+                {
+                    ulong delta = mappedEndAddress - endAddress;
+                    mappedSize -= delta;
+                }
+
+                if (!WindowsApi.VirtualProtect((IntPtr)mappedAddress, (IntPtr)mappedSize, WindowsApi.GetProtection(permission), out _))
+                {
+                    if (throwOnError)
+                    {
+                        throw new WindowsApiException("VirtualProtect");
+                    }
+
+                    success = false;
+                }
+
+                // We only keep track of "non-standard" protections,
+                // that is, everything that is not just RW (which is the default when views are mapped).
+                if (permission == MemoryPermission.ReadAndWrite)
+                {
+                    RemoveProtection(mappedAddress, mappedSize);
+                }
+                else
+                {
+                    AddProtection(mappedAddress, mappedSize, permission);
+                }
+            }
+
+            return success;
+        }
+
+        /// <summary>
+        /// Checks the result of a VirtualFree operation, throwing if needed.
+        /// </summary>
+        /// <param name="success">Operation result</param>
+        /// <exception cref="WindowsApiException">Thrown if <paramref name="success"/> is false</exception>
+        private static void CheckFreeResult(bool success)
+        {
+            if (!success)
+            {
+                throw new WindowsApiException("VirtualFree");
+            }
+        }
+
+        /// <summary>
+        /// Adds an offset to a backing offset. This will do nothing if the backing offset is the special "unmapped" value.
+        /// </summary>
+        /// <param name="backingOffset">Backing offset</param>
+        /// <param name="offset">Offset to be added</param>
+        /// <returns>Added offset or just <paramref name="backingOffset"/> if the region is unmapped</returns>
+        private static ulong AddBackingOffset(ulong backingOffset, ulong offset)
+        {
+            if (backingOffset == ulong.MaxValue)
+            {
+                return backingOffset;
+            }
+
+            return backingOffset + offset;
+        }
+
+        /// <summary>
+        /// Checks if a region is unmapped.
+        /// </summary>
+        /// <param name="backingOffset">Backing offset to check</param>
+        /// <returns>True if the backing offset is the special "unmapped" value, false otherwise</returns>
+        private static bool IsMapped(ulong backingOffset)
+        {
+            return backingOffset != ulong.MaxValue;
+        }
+
+        /// <summary>
+        /// Adds a protection to the list of protections.
+        /// </summary>
+        /// <param name="address">Address of the protected region</param>
+        /// <param name="size">Size of the protected region in bytes</param>
+        /// <param name="permission">Memory permissions of the region</param>
+        private void AddProtection(ulong address, ulong size, MemoryPermission permission)
+        {
+            ulong endAddress = address + size;
+            var overlaps = Array.Empty<IntervalTreeNode<ulong, MemoryPermission>>();
+            int count = 0;
+
+            lock (_protections)
+            {
+                count = _protections.Get(address, endAddress, ref overlaps);
+
+                Debug.Assert(count > 0);
+
+                if (count == 1 &&
+                    overlaps[0].Start <= address &&
+                    overlaps[0].End >= endAddress &&
+                    overlaps[0].Value == permission)
+                {
+                    return;
+                }
+
+                ulong startAddress = address;
+
+                for (int index = 0; index < count; index++)
+                {
+                    var protection = overlaps[index];
+
+                    ulong protAddress = protection.Start;
+                    ulong protEndAddress = protection.End;
+                    MemoryPermission protPermission = protection.Value;
+
+                    _protections.Remove(protection);
+
+                    if (protection.Value == permission)
+                    {
+                        if (startAddress > protAddress)
+                        {
+                            startAddress = protAddress;
+                        }
+
+                        if (endAddress < protEndAddress)
+                        {
+                            endAddress = protEndAddress;
+                        }
+                    }
+                    else
+                    {
+                        if (startAddress > protAddress)
+                        {
+                            _protections.Add(protAddress, startAddress, protPermission);
+                        }
+
+                        if (endAddress < protEndAddress)
+                        {
+                            _protections.Add(endAddress, protEndAddress, protPermission);
+                        }
+                    }
+                }
+
+                _protections.Add(startAddress, endAddress, permission);
+            }
+        }
+
+        /// <summary>
+        /// Removes protection from the list of protections.
+        /// </summary>
+        /// <param name="address">Address of the protected region</param>
+        /// <param name="size">Size of the protected region in bytes</param>
+        private void RemoveProtection(ulong address, ulong size)
+        {
+            ulong endAddress = address + size;
+            var overlaps = Array.Empty<IntervalTreeNode<ulong, MemoryPermission>>();
+            int count = 0;
+
+            lock (_protections)
+            {
+                count = _protections.Get(address, endAddress, ref overlaps);
+
+                for (int index = 0; index < count; index++)
+                {
+                    var protection = overlaps[index];
+
+                    ulong protAddress = protection.Start;
+                    ulong protEndAddress = protection.End;
+                    MemoryPermission protPermission = protection.Value;
+
+                    _protections.Remove(protection);
+
+                    if (address > protAddress)
+                    {
+                        _protections.Add(protAddress, address, protPermission);
+                    }
+
+                    if (endAddress < protEndAddress)
+                    {
+                        _protections.Add(endAddress, protEndAddress, protPermission);
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// Restores the protection of a given memory region that was remapped, using the protections list.
+        /// </summary>
+        /// <param name="address">Address of the remapped region</param>
+        /// <param name="size">Size of the remapped region in bytes</param>
+        private void RestoreRangeProtection(ulong address, ulong size)
+        {
+            ulong endAddress = address + size;
+            var overlaps = Array.Empty<IntervalTreeNode<ulong, MemoryPermission>>();
+            int count = 0;
+
+            lock (_protections)
+            {
+                count = _protections.Get(address, endAddress, ref overlaps);
+            }
+
+            ulong startAddress = address;
+
+            for (int index = 0; index < count; index++)
+            {
+                var protection = overlaps[index];
+
+                ulong protAddress = protection.Start;
+                ulong protEndAddress = protection.End;
+
+                if (protAddress < address)
+                {
+                    protAddress = address;
+                }
+
+                if (protEndAddress > endAddress)
+                {
+                    protEndAddress = endAddress;
+                }
+
+                ReprotectViewInternal((IntPtr)protAddress, (IntPtr)(protEndAddress - protAddress), protection.Value, true);
+            }
+        }
+
+        /// <summary>
+        /// Checks if an access violation handler should retry execution due to a fault caused by partial unmap.
+        /// </summary>
+        /// <remarks>
+        /// Due to Windows limitations, <see cref="UnmapView"/> might need to unmap more memory than requested.
+        /// The additional memory that was unmapped is later remapped, however this leaves a time gap where the
+        /// memory might be accessed but is unmapped. Users of the API must compensate for that by catching the
+        /// access violation and retrying if it happened between the unmap and remap operation.
+        /// This method can be used to decide if retrying in such cases is necessary or not.
+        /// </remarks>
+        /// <returns>True if execution should be retried, false otherwise</returns>
+        public bool RetryFromAccessViolation()
+        {
+            _partialUnmapLock.AcquireReaderLock(Timeout.Infinite);
+
+            bool retry = _threadLocalPartialUnmapsCount != _partialUnmapsCount;
+            if (retry)
+            {
+                _threadLocalPartialUnmapsCount = _partialUnmapsCount;
+            }
+
+            _partialUnmapLock.ReleaseReaderLock();
+
+            return retry;
+        }
+    }
+}

Ryujinx.Memory/WindowsShared/WindowsApi.cs

@@ -0,0 +1,93 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace Ryujinx.Memory.WindowsShared
+{
+    static class WindowsApi
+    {
+        public static readonly IntPtr InvalidHandleValue = new IntPtr(-1);
+        public static readonly IntPtr CurrentProcessHandle = new IntPtr(-1);
+
+        [DllImport("kernel32.dll", SetLastError = true)]
+        public static extern IntPtr VirtualAlloc(
+            IntPtr lpAddress,
+            IntPtr dwSize,
+            AllocationType flAllocationType,
+            MemoryProtection flProtect);
+
+        [DllImport("KernelBase.dll", SetLastError = true)]
+        public static extern IntPtr VirtualAlloc2(
+            IntPtr process,
+            IntPtr lpAddress,
+            IntPtr dwSize,
+            AllocationType flAllocationType,
+            MemoryProtection flProtect,
+            IntPtr extendedParameters,
+            ulong parameterCount);
+
+        [DllImport("kernel32.dll", SetLastError = true)]
+        public static extern bool VirtualProtect(
+            IntPtr lpAddress,
+            IntPtr dwSize,
+            MemoryProtection flNewProtect,
+            out MemoryProtection lpflOldProtect);
+
+        [DllImport("kernel32.dll", SetLastError = true)]
+        public static extern bool VirtualFree(IntPtr lpAddress, IntPtr dwSize, AllocationType dwFreeType);
+
+        [DllImport("kernel32.dll", SetLastError = true)]
+        public static extern IntPtr CreateFileMapping(
+            IntPtr hFile,
+            IntPtr lpFileMappingAttributes,
+            FileMapProtection flProtect,
+            uint dwMaximumSizeHigh,
+            uint dwMaximumSizeLow,
+            [MarshalAs(UnmanagedType.LPWStr)] string lpName);
+
+        [DllImport("kernel32.dll", SetLastError = true)]
+        public static extern bool CloseHandle(IntPtr hObject);
+
+        [DllImport("kernel32.dll", SetLastError = true)]
+        public static extern IntPtr MapViewOfFile(
+            IntPtr hFileMappingObject,
+            uint dwDesiredAccess,
+            uint dwFileOffsetHigh,
+            uint dwFileOffsetLow,
+            IntPtr dwNumberOfBytesToMap);
+
+        [DllImport("KernelBase.dll", SetLastError = true)]
+        public static extern IntPtr MapViewOfFile3(
+            IntPtr hFileMappingObject,
+            IntPtr process,
+            IntPtr baseAddress,
+            ulong offset,
+            IntPtr dwNumberOfBytesToMap,
+            ulong allocationType,
+            MemoryProtection dwDesiredAccess,
+            IntPtr extendedParameters,
+            ulong parameterCount);
+
+        [DllImport("kernel32.dll", SetLastError = true)]
+        public static extern bool UnmapViewOfFile(IntPtr lpBaseAddress);
+
+        [DllImport("KernelBase.dll", SetLastError = true)]
+        public static extern bool UnmapViewOfFile2(IntPtr process, IntPtr lpBaseAddress, ulong unmapFlags);
+
+        [DllImport("kernel32.dll")]
+        public static extern uint GetLastError();
+
+        public static MemoryProtection GetProtection(MemoryPermission permission)
+        {
+            return permission switch
+            {
+                MemoryPermission.None => MemoryProtection.NoAccess,
+                MemoryPermission.Read => MemoryProtection.ReadOnly,
+                MemoryPermission.ReadAndWrite => MemoryProtection.ReadWrite,
+                MemoryPermission.ReadAndExecute => MemoryProtection.ExecuteRead,
+                MemoryPermission.ReadWriteExecute => MemoryProtection.ExecuteReadWrite,
+                MemoryPermission.Execute => MemoryProtection.Execute,
+                _ => throw new MemoryProtectionException(permission)
+            };
+        }
+    }
+}

Ryujinx.Memory/WindowsShared/WindowsApiException.cs

@@ -0,0 +1,24 @@
+using System;
+
+namespace Ryujinx.Memory.WindowsShared
+{
+    class WindowsApiException : Exception
+    {
+        public WindowsApiException()
+        {
+        }
+
+        public WindowsApiException(string functionName) : base(CreateMessage(functionName))
+        {
+        }
+
+        public WindowsApiException(string functionName, Exception inner) : base(CreateMessage(functionName), inner)
+        {
+        }
+
+        private static string CreateMessage(string functionName)
+        {
+            return $"{functionName} returned error code 0x{WindowsApi.GetLastError():X}.";
+        }
+    }
+}

Ryujinx.Tests/Cpu/CpuTest.cs

@@ -54,9 +54,9 @@ namespace Ryujinx.Tests.Cpu
             _currAddress = CodeBaseAddress;
 
             _ram = new MemoryBlock(Size * 2);
-            _memory = new MemoryManager(1ul << 16);
+            _memory = new MemoryManager(_ram, 1ul << 16);
             _memory.IncrementReferenceCount();
-            _memory.Map(CodeBaseAddress, _ram.GetPointer(0, Size * 2), Size * 2);
+            _memory.Map(CodeBaseAddress, 0, Size * 2);
 
             _context = CpuContext.CreateExecutionContext();
             Translator.IsReadyForTranslation.Set();

Ryujinx.Tests/Cpu/CpuTest32.cs

@@ -49,9 +49,9 @@ namespace Ryujinx.Tests.Cpu
             _currAddress = CodeBaseAddress;
 
             _ram = new MemoryBlock(Size * 2);
-            _memory = new MemoryManager(1ul << 16);
+            _memory = new MemoryManager(_ram, 1ul << 16);
             _memory.IncrementReferenceCount();
-            _memory.Map(CodeBaseAddress, _ram.GetPointer(0, Size * 2), Size * 2);
+            _memory.Map(CodeBaseAddress, 0, Size * 2);
 
             _context = CpuContext.CreateExecutionContext();
             _context.IsAarch32 = true;