e2c9784325
Documentation: The Drivers Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
127 lines
5 KiB
C
127 lines
5 KiB
C
#ifndef _ASM_LGUEST_USER
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#define _ASM_LGUEST_USER
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/* Everything the "lguest" userspace program needs to know. */
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/* They can register up to 32 arrays of lguest_dma. */
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#define LGUEST_MAX_DMA 32
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/* At most we can dma 16 lguest_dma in one op. */
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#define LGUEST_MAX_DMA_SECTIONS 16
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/* How many devices? Assume each one wants up to two dma arrays per device. */
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#define LGUEST_MAX_DEVICES (LGUEST_MAX_DMA/2)
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/*D:200
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* Lguest I/O
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*
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* The lguest I/O mechanism is the only way Guests can talk to devices. There
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* are two hypercalls involved: SEND_DMA for output and BIND_DMA for input. In
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* each case, "struct lguest_dma" describes the buffer: this contains 16
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* addr/len pairs, and if there are fewer buffer elements the len array is
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* terminated with a 0.
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*
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* I/O is organized by keys: BIND_DMA attaches buffers to a particular key, and
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* SEND_DMA transfers to buffers bound to particular key. By convention, keys
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* correspond to a physical address within the device's page. This means that
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* devices will never accidentally end up with the same keys, and allows the
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* Host use The Futex Trick (as we'll see later in our journey).
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*
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* SEND_DMA simply indicates a key to send to, and the physical address of the
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* "struct lguest_dma" to send. The Host will write the number of bytes
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* transferred into the "struct lguest_dma"'s used_len member.
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*
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* BIND_DMA indicates a key to bind to, a pointer to an array of "struct
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* lguest_dma"s ready for receiving, the size of that array, and an interrupt
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* to trigger when data is received. The Host will only allow transfers into
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* buffers with a used_len of zero: it then sets used_len to the number of
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* bytes transferred and triggers the interrupt for the Guest to process the
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* new input. */
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struct lguest_dma
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{
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/* 0 if free to be used, filled by the Host. */
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u32 used_len;
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unsigned long addr[LGUEST_MAX_DMA_SECTIONS];
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u16 len[LGUEST_MAX_DMA_SECTIONS];
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};
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/*:*/
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/*D:460 This is the layout of a block device memory page. The Launcher sets up
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* the num_sectors initially to tell the Guest the size of the disk. The Guest
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* puts the type, sector and length of the request in the first three fields,
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* then DMAs to the Host. The Host processes the request, sets up the result,
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* then DMAs back to the Guest. */
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struct lguest_block_page
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{
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/* 0 is a read, 1 is a write. */
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int type;
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u32 sector; /* Offset in device = sector * 512. */
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u32 bytes; /* Length expected to be read/written in bytes */
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/* 0 = pending, 1 = done, 2 = done, error */
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int result;
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u32 num_sectors; /* Disk length = num_sectors * 512 */
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};
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/*D:520 The network device is basically a memory page where all the Guests on
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* the network publish their MAC (ethernet) addresses: it's an array of "struct
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* lguest_net": */
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struct lguest_net
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{
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/* Simply the mac address (with multicast bit meaning promisc). */
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unsigned char mac[6];
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};
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/*:*/
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/* Where the Host expects the Guest to SEND_DMA console output to. */
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#define LGUEST_CONSOLE_DMA_KEY 0
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/*D:010
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* Drivers
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*
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* The Guest needs devices to do anything useful. Since we don't let it touch
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* real devices (think of the damage it could do!) we provide virtual devices.
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* We could emulate a PCI bus with various devices on it, but that is a fairly
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* complex burden for the Host and suboptimal for the Guest, so we have our own
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* "lguest" bus and simple drivers.
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*
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* Devices are described by an array of LGUEST_MAX_DEVICES of these structs,
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* placed by the Launcher just above the top of physical memory:
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*/
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struct lguest_device_desc {
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/* The device type: console, network, disk etc. */
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u16 type;
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#define LGUEST_DEVICE_T_CONSOLE 1
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#define LGUEST_DEVICE_T_NET 2
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#define LGUEST_DEVICE_T_BLOCK 3
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/* The specific features of this device: these depends on device type
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* except for LGUEST_DEVICE_F_RANDOMNESS. */
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u16 features;
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#define LGUEST_NET_F_NOCSUM 0x4000 /* Don't bother checksumming */
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#define LGUEST_DEVICE_F_RANDOMNESS 0x8000 /* IRQ is fairly random */
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/* This is how the Guest reports status of the device: the Host can set
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* LGUEST_DEVICE_S_REMOVED to indicate removal, but the rest are only
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* ever manipulated by the Guest, and only ever set. */
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u16 status;
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/* 256 and above are device specific. */
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#define LGUEST_DEVICE_S_ACKNOWLEDGE 1 /* We have seen device. */
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#define LGUEST_DEVICE_S_DRIVER 2 /* We have found a driver */
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#define LGUEST_DEVICE_S_DRIVER_OK 4 /* Driver says OK! */
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#define LGUEST_DEVICE_S_REMOVED 8 /* Device has gone away. */
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#define LGUEST_DEVICE_S_REMOVED_ACK 16 /* Driver has been told. */
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#define LGUEST_DEVICE_S_FAILED 128 /* Something actually failed */
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/* Each device exists somewhere in Guest physical memory, over some
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* number of pages. */
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u16 num_pages;
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u32 pfn;
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};
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/*:*/
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/* Write command first word is a request. */
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enum lguest_req
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{
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LHREQ_INITIALIZE, /* + pfnlimit, pgdir, start, pageoffset */
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LHREQ_GETDMA, /* + addr (returns &lguest_dma, irq in ->used_len) */
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LHREQ_IRQ, /* + irq */
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LHREQ_BREAK, /* + on/off flag (on blocks until someone does off) */
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};
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#endif /* _ASM_LGUEST_USER */
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