165 lines
5.4 KiB
C
165 lines
5.4 KiB
C
/*-
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* Copyright Rusty Russell IBM Corporation 2007.
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*
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* This header is BSD licensed so anyone can use the definitions to implement
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* compatible drivers/servers.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of IBM nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#ifndef VIRTIO_RING_H
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#define VIRTIO_RING_H
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/* This marks a buffer as continuing via the next field. */
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#define VRING_DESC_F_NEXT 1
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/* This marks a buffer as write-only (otherwise read-only). */
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#define VRING_DESC_F_WRITE 2
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/* This means the buffer contains a list of buffer descriptors. */
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#define VRING_DESC_F_INDIRECT 4
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/* The Host uses this in used->flags to advise the Guest: don't kick me
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* when you add a buffer. It's unreliable, so it's simply an
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* optimization. Guest will still kick if it's out of buffers. */
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#define VRING_USED_F_NO_NOTIFY 1
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/* The Guest uses this in avail->flags to advise the Host: don't
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* interrupt me when you consume a buffer. It's unreliable, so it's
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* simply an optimization. */
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#define VRING_AVAIL_F_NO_INTERRUPT 1
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/* VirtIO ring descriptors: 16 bytes.
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* These can chain together via "next". */
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struct vring_desc {
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/* Address (guest-physical). */
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uint64_t addr;
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/* Length. */
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uint32_t len;
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/* The flags as indicated above. */
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uint16_t flags;
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/* We chain unused descriptors via this, too. */
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uint16_t next;
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};
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struct vring_avail {
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uint16_t flags;
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uint16_t idx;
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uint16_t ring[0];
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};
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/* uint32_t is used here for ids for padding reasons. */
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struct vring_used_elem {
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/* Index of start of used descriptor chain. */
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uint32_t id;
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/* Total length of the descriptor chain which was written to. */
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uint32_t len;
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};
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struct vring_used {
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uint16_t flags;
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uint16_t idx;
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struct vring_used_elem ring[0];
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};
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struct vring {
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unsigned int num;
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struct vring_desc *desc;
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struct vring_avail *avail;
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struct vring_used *used;
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};
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/* The standard layout for the ring is a continuous chunk of memory which
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* looks like this. We assume num is a power of 2.
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*
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* struct vring {
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* // The actual descriptors (16 bytes each)
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* struct vring_desc desc[num];
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*
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* // A ring of available descriptor heads with free-running index.
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* __u16 avail_flags;
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* __u16 avail_idx;
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* __u16 available[num];
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* __u16 used_event_idx;
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*
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* // Padding to the next align boundary.
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* char pad[];
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*
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* // A ring of used descriptor heads with free-running index.
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* __u16 used_flags;
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* __u16 used_idx;
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* struct vring_used_elem used[num];
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* __u16 avail_event_idx;
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* };
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*
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* NOTE: for VirtIO PCI, align is 4096.
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*/
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/*
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* We publish the used event index at the end of the available ring, and vice
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* versa. They are at the end for backwards compatibility.
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*/
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#define vring_used_event(vr) ((vr)->avail->ring[(vr)->num])
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#define vring_avail_event(vr) (*(uint16_t *)&(vr)->used->ring[(vr)->num])
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static inline int
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vring_size(unsigned int num, unsigned long align)
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{
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int size;
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size = num * sizeof(struct vring_desc);
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size += sizeof(struct vring_avail) + (num * sizeof(uint16_t));
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size = (size + align - 1) & ~(align - 1);
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size += sizeof(struct vring_used) +
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(num * sizeof(struct vring_used_elem));
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return (size);
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}
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static inline void
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vring_init(struct vring *vr, unsigned int num, uint8_t *p,
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unsigned long align)
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{
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vr->num = num;
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vr->desc = (struct vring_desc *) p;
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vr->avail = (struct vring_avail *) (p +
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num * sizeof(struct vring_desc));
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vr->used = (void *)
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(((unsigned long) &vr->avail->ring[num] + align-1) & ~(align-1));
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}
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/*
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* The following is used with VIRTIO_RING_F_EVENT_IDX.
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*
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* Assuming a given event_idx value from the other size, if we have
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* just incremented index from old to new_idx, should we trigger an
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* event?
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*/
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static inline int
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vring_need_event(uint16_t event_idx, uint16_t new_idx, uint16_t old)
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{
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return (uint16_t)(new_idx - event_idx - 1) < (uint16_t)(new_idx - old);
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}
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#endif /* VIRTIO_RING_H */
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