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#ifndef VIRTIO_RING_H
#define VIRTIO_RING_H
/* An interface for efficient virtio implementation.
*
* This header is BSD licensed so anyone can use the definitions
* to implement compatible drivers/servers.
*
* Copyright 2007, 2009, IBM Corporation
* Copyright 2011, Red Hat, Inc
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of IBM nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <stdint.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
/* Support for indirect descriptors */
#define VIRTIO_RING_F_INDIRECT_DESC 28
/* Support for avail_idx and used_idx fields */
#define VIRTIO_RING_F_EVENT_IDX 29
/* Arbitrary descriptor layouts. */
#define VIRTIO_F_ANY_LAYOUT 27
/* Virtio ring descriptors: 16 bytes.
* These can chain together via "next". */
struct vring_desc {
/* Address (guest-physical). */
le64 addr;
/* Length. */
le32 len;
/* The flags as indicated above. */
le16 flags;
/* We chain unused descriptors via this, too */
le16 next;
};
struct vring_avail {
le16 flags;
le16 idx;
le16 ring[];
/* Only if VIRTIO_RING_F_EVENT_IDX: le16 used_event; */
};
/* le32 is used here for ids for padding reasons. */
struct vring_used_elem {
/* Index of start of used descriptor chain. */
le32 id;
/* Total length of the descriptor chain which was written to. */
le32 len;
};
struct vring_used {
le16 flags;
le16 idx;
struct vring_used_elem ring[];
/* Only if VIRTIO_RING_F_EVENT_IDX: le16 avail_event; */
};
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.
* le16 avail_flags;
* le16 avail_idx;
* le16 available[num];
* le16 used_event_idx; // Only if VIRTIO_RING_F_EVENT_IDX
*
* // Padding to the next align boundary.
* char pad[];
*
* // A ring of used descriptor heads with free-running index.
* le16 used_flags;
* le16 used_idx;
* struct vring_used_elem used[num];
* le16 avail_event_idx; // Only if VIRTIO_RING_F_EVENT_IDX
* };
* Note: for virtio PCI, align is 4096.
*/
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] + sizeof(le16)
+ align-1)
& ~(align - 1));
}
static inline unsigned vring_size(unsigned int num, unsigned long align)
{
return ((sizeof(struct vring_desc)*num + sizeof(le16)*(3+num)
+ align - 1) & ~(align - 1))
+ sizeof(le16)*3 + sizeof(struct vring_used_elem)*num;
}
static inline int vring_need_event(uint16_t event_idx, uint16_t new_idx, uint16_t old_idx)
{
return (uint16_t)(new_idx - event_idx - 1) < (uint16_t)(new_idx - old_idx);
}
/* Get location of event indices (only with VIRTIO_RING_F_EVENT_IDX) */
static inline le16 *vring_used_event(struct vring *vr)
{
/* For backwards compat, used event index is at *end* of avail ring. */
return &vr->avail->ring[vr->num];
}
static inline le16 *vring_avail_event(struct vring *vr)
{
/* For backwards compat, avail event index is at *end* of used ring. */
return (le16 *)&vr->used->ring[vr->num];
}
#endif /* VIRTIO_RING_H */
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