virtio_ring.h revision 228301
1228301Sgrehan/*- 2228301Sgrehan * Copyright Rusty Russell IBM Corporation 2007. 3227652Sgrehan * 4228301Sgrehan * This header is BSD licensed so anyone can use the definitions to implement 5228301Sgrehan * compatible drivers/servers. 6228301Sgrehan * 7228301Sgrehan * Redistribution and use in source and binary forms, with or without 8228301Sgrehan * modification, are permitted provided that the following conditions 9228301Sgrehan * are met: 10228301Sgrehan * 1. Redistributions of source code must retain the above copyright 11228301Sgrehan * notice, this list of conditions and the following disclaimer. 12228301Sgrehan * 2. Redistributions in binary form must reproduce the above copyright 13228301Sgrehan * notice, this list of conditions and the following disclaimer in the 14228301Sgrehan * documentation and/or other materials provided with the distribution. 15228301Sgrehan * 3. Neither the name of IBM nor the names of its contributors 16228301Sgrehan * may be used to endorse or promote products derived from this software 17228301Sgrehan * without specific prior written permission. 18228301Sgrehan * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 19228301Sgrehan * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 20228301Sgrehan * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 21228301Sgrehan * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE 22228301Sgrehan * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23228301Sgrehan * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24228301Sgrehan * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25228301Sgrehan * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26228301Sgrehan * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27228301Sgrehan * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28228301Sgrehan * SUCH DAMAGE. 29228301Sgrehan * 30228301Sgrehan * $FreeBSD: head/sys/dev/virtio/virtio_ring.h 228301 2011-12-06 06:28:32Z grehan $ 31227652Sgrehan */ 32227652Sgrehan 33227652Sgrehan#ifndef VIRTIO_RING_H 34227652Sgrehan#define VIRTIO_RING_H 35227652Sgrehan 36227652Sgrehan#include <sys/types.h> 37227652Sgrehan 38227652Sgrehan/* This marks a buffer as continuing via the next field. */ 39227652Sgrehan#define VRING_DESC_F_NEXT 1 40227652Sgrehan/* This marks a buffer as write-only (otherwise read-only). */ 41227652Sgrehan#define VRING_DESC_F_WRITE 2 42227652Sgrehan/* This means the buffer contains a list of buffer descriptors. */ 43227652Sgrehan#define VRING_DESC_F_INDIRECT 4 44227652Sgrehan 45227652Sgrehan/* The Host uses this in used->flags to advise the Guest: don't kick me 46227652Sgrehan * when you add a buffer. It's unreliable, so it's simply an 47227652Sgrehan * optimization. Guest will still kick if it's out of buffers. */ 48227652Sgrehan#define VRING_USED_F_NO_NOTIFY 1 49227652Sgrehan/* The Guest uses this in avail->flags to advise the Host: don't 50227652Sgrehan * interrupt me when you consume a buffer. It's unreliable, so it's 51227652Sgrehan * simply an optimization. */ 52227652Sgrehan#define VRING_AVAIL_F_NO_INTERRUPT 1 53227652Sgrehan 54227652Sgrehan/* VirtIO ring descriptors: 16 bytes. 55227652Sgrehan * These can chain together via "next". */ 56227652Sgrehanstruct vring_desc { 57227652Sgrehan /* Address (guest-physical). */ 58227652Sgrehan uint64_t addr; 59227652Sgrehan /* Length. */ 60227652Sgrehan uint32_t len; 61227652Sgrehan /* The flags as indicated above. */ 62227652Sgrehan uint16_t flags; 63227652Sgrehan /* We chain unused descriptors via this, too. */ 64227652Sgrehan uint16_t next; 65227652Sgrehan}; 66227652Sgrehan 67227652Sgrehanstruct vring_avail { 68227652Sgrehan uint16_t flags; 69227652Sgrehan uint16_t idx; 70227652Sgrehan uint16_t ring[0]; 71227652Sgrehan}; 72227652Sgrehan 73227652Sgrehan/* uint32_t is used here for ids for padding reasons. */ 74227652Sgrehanstruct vring_used_elem { 75227652Sgrehan /* Index of start of used descriptor chain. */ 76227652Sgrehan uint32_t id; 77227652Sgrehan /* Total length of the descriptor chain which was written to. */ 78227652Sgrehan uint32_t len; 79227652Sgrehan}; 80227652Sgrehan 81227652Sgrehanstruct vring_used { 82227652Sgrehan uint16_t flags; 83227652Sgrehan uint16_t idx; 84227652Sgrehan struct vring_used_elem ring[0]; 85227652Sgrehan}; 86227652Sgrehan 87227652Sgrehanstruct vring { 88227652Sgrehan unsigned int num; 89227652Sgrehan 90227652Sgrehan struct vring_desc *desc; 91227652Sgrehan struct vring_avail *avail; 92227652Sgrehan struct vring_used *used; 93227652Sgrehan}; 94227652Sgrehan 95227652Sgrehan/* The standard layout for the ring is a continuous chunk of memory which 96227652Sgrehan * looks like this. We assume num is a power of 2. 97227652Sgrehan * 98227652Sgrehan * struct vring { 99227652Sgrehan * // The actual descriptors (16 bytes each) 100227652Sgrehan * struct vring_desc desc[num]; 101227652Sgrehan * 102227652Sgrehan * // A ring of available descriptor heads with free-running index. 103227652Sgrehan * __u16 avail_flags; 104227652Sgrehan * __u16 avail_idx; 105227652Sgrehan * __u16 available[num]; 106227652Sgrehan * 107227652Sgrehan * // Padding to the next align boundary. 108227652Sgrehan * char pad[]; 109227652Sgrehan * 110227652Sgrehan * // A ring of used descriptor heads with free-running index. 111227652Sgrehan * __u16 used_flags; 112227652Sgrehan * __u16 used_idx; 113227652Sgrehan * struct vring_used_elem used[num]; 114227652Sgrehan * }; 115227652Sgrehan * 116227652Sgrehan * NOTE: for VirtIO PCI, align is 4096. 117227652Sgrehan */ 118227652Sgrehan 119227652Sgrehanstatic inline int 120227652Sgrehanvring_size(unsigned int num, unsigned long align) 121227652Sgrehan{ 122227652Sgrehan int size; 123227652Sgrehan 124227652Sgrehan size = num * sizeof(struct vring_desc); 125227652Sgrehan size += sizeof(struct vring_avail) + (num * sizeof(uint16_t)); 126227652Sgrehan size = (size + align - 1) & ~(align - 1); 127227652Sgrehan size += sizeof(struct vring_used) + 128227652Sgrehan (num * sizeof(struct vring_used_elem)); 129227652Sgrehan return (size); 130227652Sgrehan} 131227652Sgrehan 132227652Sgrehanstatic inline void 133227652Sgrehanvring_init(struct vring *vr, unsigned int num, uint8_t *p, 134227652Sgrehan unsigned long align) 135227652Sgrehan{ 136227652Sgrehan vr->num = num; 137227652Sgrehan vr->desc = (struct vring_desc *) p; 138227652Sgrehan vr->avail = (struct vring_avail *) (p + 139227652Sgrehan num * sizeof(struct vring_desc)); 140227652Sgrehan vr->used = (void *) 141227652Sgrehan (((unsigned long) &vr->avail->ring[num] + align-1) & ~(align-1)); 142227652Sgrehan} 143227652Sgrehan#endif /* VIRTIO_RING_H */ 144