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/* SPDX-License-Identifier: BSD-3-Clause
* Copyright(c) 2010-2014 Intel Corporation
*/
#ifndef _VIRTIO_RING_H_
#define _VIRTIO_RING_H_
#include <stdint.h>
#include <rte_common.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 {
uint64_t addr; /* Address (guest-physical). */
uint32_t len; /* Length. */
uint16_t flags; /* The flags as indicated above. */
uint16_t next; /* We chain unused descriptors via this. */
};
struct vring_avail {
uint16_t flags;
uint16_t idx;
uint16_t ring[0];
};
/* id is a 16bit index. 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;
volatile 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 size_t
vring_size(unsigned int num, unsigned long align)
{
size_t size;
size = num * sizeof(struct vring_desc);
size += sizeof(struct vring_avail) + (num * sizeof(uint16_t));
size = RTE_ALIGN_CEIL(size, align);
size += sizeof(struct vring_used) +
(num * sizeof(struct vring_used_elem));
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 *)
RTE_ALIGN_CEIL((uintptr_t)(&vr->avail->ring[num]), align);
}
/*
* 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_ */
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