/*-
* Copyright Rusty Russell IBM Corporation 2007.
*
* This header is BSD licensed so anyone can use the definitions to implement
* compatible drivers/servers.
*
* 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.
*
* $FreeBSD$
*/
#ifndef VIRTIO_RING_H
#define VIRTIO_RING_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
/* 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[0];
};
/* 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 written to. */
uint32_t len;
};
struct vring_used {
uint16_t flags;
uint16_t idx;
struct vring_used_elem ring[0];
};
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.
* __u16 avail_flags;
* __u16 avail_idx;
* __u16 available[num];
* __u16 used_event_idx;
*
* // Padding to the next align boundary.
* char pad[];
*
* // A ring of used descriptor heads with free-running index.
* __u16 used_flags;
* __u16 used_idx;
* struct vring_used_elem used[num];
* __u16 avail_event_idx;
* };
*
* NOTE: for VirtIO PCI, align is 4096.
*/
/*
* We publish the used event index at the end of the available ring, and vice
* versa. They are at the end for backwards compatibility.
*/
#define vring_used_event(vr) ((vr)->avail->ring[(vr)->num])
#define vring_avail_event(vr) (*(uint16_t *)&(vr)->used->ring[(vr)->num])
static inline int
vring_size(unsigned int num, unsigned long align)
{
int size;
size = num * sizeof(struct vring_desc);
size += sizeof(struct vring_avail) + (num * sizeof(uint16_t)) +
sizeof(uint16_t);
size = (size + align - 1) & ~(align - 1);
size += sizeof(struct vring_used) +
(num * sizeof(struct vring_used_elem)) + sizeof(uint16_t);
return (size);
}
static inline void
vring_init(struct vring *vr, unsigned int num, uint8_t *p,
unsigned long align)
{
vr->num = num;
vr->desc = (struct vring_desc *) p;
vr->avail = (struct vring_avail *) (p +
num * sizeof(struct vring_desc));
vr->used = (void *)
(((unsigned long) &vr->avail->ring[num] + align-1) & ~(align-1));
}
/*
* The following is used with VIRTIO_RING_F_EVENT_IDX.
*
* Assuming a given event_idx value from the other size, if we have
* just incremented index from old to new_idx, should we trigger an
* event?
*/
static inline int
vring_need_event(uint16_t event_idx, uint16_t new_idx, uint16_t old)
{
return (uint16_t)(new_idx - event_idx - 1) < (uint16_t)(new_idx - old);
}
#endif /* VIRTIO_RING_H */
