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kvm: Add virtio_ring.h to tree

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This patch adds virtio_ring.h from Linux kernel sources to the tree. We will
need it to implement virtio block device emulation.

Signed-off-by: Cyrill Gorcunov <gorcunov@gmail.com>
This commit is contained in:
Cyrill Gorcunov
2015-06-01 16:39:40 +01:00
committed by Will Deacon
parent 8b1ff07e1f
commit b3099f5d38
1 changed files with 107 additions and 0 deletions
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include/kvm/virtio_ring.h
+107
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/*
* Code is taken from include/linux/virtio_ring.h
*/
#ifndef _LINUX_VIRTIO_RING_H
#define _LINUX_VIRTIO_RING_H
#include <inttypes.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 the buffer contains a list of buffer descriptors. */
#define VRING_DESC_F_INDIRECT 4
/* The Host uses this in used->flags to advise the Guest: don't kick me when
* you add a buffer. It's unreliable, so it's simply an optimization. Guest
* will still kick if it's out of buffers. */
#define VRING_USED_F_NO_NOTIFY 1
/* The Guest uses this in avail->flags to advise the Host: don't interrupt me
* when you consume a buffer. It's unreliable, so it's simply an
* optimization. */
#define VRING_AVAIL_F_NO_INTERRUPT 1
/* We support indirect buffer descriptors */
#define VIRTIO_RING_F_INDIRECT_DESC 28
/* Virtio ring descriptors: 16 bytes. These can chain together via "next". */
struct vring_desc {
/* Address (guest-physical). */
uint64_t addr;
/* Length. */
uint32_t len;
/* The flags as indicated above. */
uint16_t flags;
/* We chain unused descriptors via this, too */
uint16_t next;
};
struct vring_avail {
uint16_t flags;
uint16_t idx;
uint16_t ring[];
};
/* uint32_t is used here for ids for padding reasons. */
struct vring_used_elem {
/* Index of start of used descriptor chain. */
uint32_t id;
/* Total length of the descriptor chain which was used (written to) */
uint32_t len;
};
struct vring_used {
uint16_t flags;
uint16_t 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. We assume num is a power of 2.
*
* struct vring
* {
* // The actual descriptors (16 bytes each)
* struct vring_desc desc[num];
*
* // A ring of available descriptor heads with free-running index.
* uint16_t avail_flags;
* uint16_t avail_idx;
* uint16_t available[num];
*
* // Padding to the next align boundary.
* char pad[];
*
* // A ring of used descriptor heads with free-running index.
* uint16_t used_flags;
* uint16_t used_idx;
* struct vring_used_elem used[num];
* };
*/
static inline void vring_init(struct vring *vr, unsigned int num, void *p,
unsigned long align)
{
vr->num = num;
vr->desc = p;
vr->avail = p + num*sizeof(struct vring_desc);
vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + align-1)
& ~(align - 1));
}
static inline unsigned vring_size(unsigned int num, unsigned long align)
{
return ((sizeof(struct vring_desc) * num + sizeof(uint16_t) * (2 + num)
+ align - 1) & ~(align - 1)) + sizeof(uint16_t) * 2
+ sizeof(struct vring_used_elem) * num;
}
#endif /* _LINUX_VIRTIO_RING_H */