0a8a69dd77
These helper routines supply most of the virtqueue_ops for hypervisors which want to use a ring for virtio. Unlike the previous lguest implementation: 1) The rings are variable sized (2^n-1 elements). 2) They have an unfortunate limit of 65535 bytes per sg element. 3) The page numbers are always 64 bit (PAE anyone?) 4) They no longer place used[] on a separate page, just a separate cacheline. 5) We do a modulo on a variable. We could be tricky if we cared. 6) Interrupts and notifies are suppressed using flags within the rings. Users need only get the ring pages and provide a notify hook (KVM wants the guest to allocate the rings, lguest does it sanely). Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Cc: Dor Laor <dor.laor@qumranet.com>
119 lines
3.1 KiB
C
119 lines
3.1 KiB
C
#ifndef _LINUX_VIRTIO_RING_H
|
|
#define _LINUX_VIRTIO_RING_H
|
|
/* An interface for efficient virtio implementation, currently for use by KVM
|
|
* and lguest, but hopefully others soon. Do NOT change this since it will
|
|
* break existing servers and clients.
|
|
*
|
|
* This header is BSD licensed so anyone can use the definitions to implement
|
|
* compatible drivers/servers.
|
|
*
|
|
* Copyright Rusty Russell IBM Corporation 2007. */
|
|
#include <linux/types.h>
|
|
|
|
/* This marks a buffer as continuing via the next field. */
|
|
#define VRING_DESC_F_NEXT 1
|
|
/* This marks a buffer as write-only (otherwise read-only). */
|
|
#define VRING_DESC_F_WRITE 2
|
|
|
|
/* This means don't notify other side when buffer added. */
|
|
#define VRING_USED_F_NO_NOTIFY 1
|
|
/* This means don't interrupt guest when buffer consumed. */
|
|
#define VRING_AVAIL_F_NO_INTERRUPT 1
|
|
|
|
/* Virtio ring descriptors: 16 bytes. These can chain together via "next". */
|
|
struct vring_desc
|
|
{
|
|
/* Address (guest-physical). */
|
|
__u64 addr;
|
|
/* Length. */
|
|
__u32 len;
|
|
/* The flags as indicated above. */
|
|
__u16 flags;
|
|
/* We chain unused descriptors via this, too */
|
|
__u16 next;
|
|
};
|
|
|
|
struct vring_avail
|
|
{
|
|
__u16 flags;
|
|
__u16 idx;
|
|
__u16 ring[];
|
|
};
|
|
|
|
/* u32 is used here for ids for padding reasons. */
|
|
struct vring_used_elem
|
|
{
|
|
/* Index of start of used descriptor chain. */
|
|
__u32 id;
|
|
/* Total length of the descriptor chain which was used (written to) */
|
|
__u32 len;
|
|
};
|
|
|
|
struct vring_used
|
|
{
|
|
__u16 flags;
|
|
__u16 idx;
|
|
struct vring_used_elem ring[];
|
|
};
|
|
|
|
struct vring {
|
|
unsigned int num;
|
|
|
|
struct vring_desc *desc;
|
|
|
|
struct vring_avail *avail;
|
|
|
|
struct vring_used *used;
|
|
};
|
|
|
|
/* The standard layout for the ring is a continuous chunk of memory which looks
|
|
* like this. The used fields will be aligned to a "num+1" boundary.
|
|
*
|
|
* struct vring
|
|
* {
|
|
* // The actual descriptors (16 bytes each)
|
|
* struct vring_desc desc[num];
|
|
*
|
|
* // A ring of available descriptor heads with free-running index.
|
|
* __u16 avail_flags;
|
|
* __u16 avail_idx;
|
|
* __u16 available[num];
|
|
*
|
|
* // Padding so a correctly-chosen num value will cache-align used_idx.
|
|
* char pad[sizeof(struct vring_desc) - sizeof(avail_flags)];
|
|
*
|
|
* // A ring of used descriptor heads with free-running index.
|
|
* __u16 used_flags;
|
|
* __u16 used_idx;
|
|
* struct vring_used_elem used[num];
|
|
* };
|
|
*/
|
|
static inline void vring_init(struct vring *vr, unsigned int num, void *p)
|
|
{
|
|
vr->num = num;
|
|
vr->desc = p;
|
|
vr->avail = p + num*sizeof(struct vring);
|
|
vr->used = p + (num+1)*(sizeof(struct vring) + sizeof(__u16));
|
|
}
|
|
|
|
static inline unsigned vring_size(unsigned int num)
|
|
{
|
|
return (num + 1) * (sizeof(struct vring_desc) + sizeof(__u16))
|
|
+ sizeof(__u32) + num * sizeof(struct vring_used_elem);
|
|
}
|
|
|
|
#ifdef __KERNEL__
|
|
#include <linux/irqreturn.h>
|
|
struct virtio_device;
|
|
struct virtqueue;
|
|
|
|
struct virtqueue *vring_new_virtqueue(unsigned int num,
|
|
struct virtio_device *vdev,
|
|
void *pages,
|
|
void (*notify)(struct virtqueue *vq),
|
|
bool (*callback)(struct virtqueue *vq));
|
|
void vring_del_virtqueue(struct virtqueue *vq);
|
|
|
|
irqreturn_t vring_interrupt(int irq, void *_vq);
|
|
#endif /* __KERNEL__ */
|
|
#endif /* _LINUX_VIRTIO_RING_H */
|