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1 : : #ifndef _LINUX_VIRTIO_RING_H 2 : : #define _LINUX_VIRTIO_RING_H 3 : : /* An interface for efficient virtio implementation, currently for use by KVM, 4 : : * but hopefully others soon. Do NOT change this since it will 5 : : * break existing servers and clients. 6 : : * 7 : : * This header is BSD licensed so anyone can use the definitions to implement 8 : : * compatible drivers/servers. 9 : : * 10 : : * Redistribution and use in source and binary forms, with or without 11 : : * modification, are permitted provided that the following conditions 12 : : * are met: 13 : : * 1. Redistributions of source code must retain the above copyright 14 : : * notice, this list of conditions and the following disclaimer. 15 : : * 2. Redistributions in binary form must reproduce the above copyright 16 : : * notice, this list of conditions and the following disclaimer in the 17 : : * documentation and/or other materials provided with the distribution. 18 : : * 3. Neither the name of IBM nor the names of its contributors 19 : : * may be used to endorse or promote products derived from this software 20 : : * without specific prior written permission. 21 : : * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS ``AS IS 22 : : '' AND 23 : : * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 : : * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 : : * ARE DISCLAIMED. IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE 26 : : * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 : : * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 : : * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 : : * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 : : * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 : : * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 : : * SUCH DAMAGE. 33 : : * 34 : : * Copyright Rusty Russell IBM Corporation 2007. */ 35 : : #ifndef __KERNEL__ 36 : : #include <stdint.h> 37 : : #endif 38 : : #include <linux/types.h> 39 : : #include <linux/virtio_types.h> 40 : : 41 : : /* This marks a buffer as continuing via the next field. */ 42 : : #define VRING_DESC_F_NEXT 1 43 : : /* This marks a buffer as write-only (otherwise read-only). */ 44 : : #define VRING_DESC_F_WRITE 2 45 : : /* This means the buffer contains a list of buffer descriptors. */ 46 : : #define VRING_DESC_F_INDIRECT 4 47 : : 48 : : /* 49 : : * Mark a descriptor as available or used in packed ring. 50 : : * Notice: they are defined as shifts instead of shifted values. 51 : : */ 52 : : #define VRING_PACKED_DESC_F_AVAIL 7 53 : : #define VRING_PACKED_DESC_F_USED 15 54 : : 55 : : /* The Host uses this in used->flags to advise the Guest: don't kick me when 56 : : * you add a buffer. It's unreliable, so it's simply an optimization. Guest 57 : : * will still kick if it's out of buffers. */ 58 : : #define VRING_USED_F_NO_NOTIFY 1 59 : : /* The Guest uses this in avail->flags to advise the Host: don't interrupt me 60 : : * when you consume a buffer. It's unreliable, so it's simply an 61 : : * optimization. */ 62 : : #define VRING_AVAIL_F_NO_INTERRUPT 1 63 : : 64 : : /* Enable events in packed ring. */ 65 : : #define VRING_PACKED_EVENT_FLAG_ENABLE 0x0 66 : : /* Disable events in packed ring. */ 67 : : #define VRING_PACKED_EVENT_FLAG_DISABLE 0x1 68 : : /* 69 : : * Enable events for a specific descriptor in packed ring. 70 : : * (as specified by Descriptor Ring Change Event Offset/Wrap Counter). 71 : : * Only valid if VIRTIO_RING_F_EVENT_IDX has been negotiated. 72 : : */ 73 : : #define VRING_PACKED_EVENT_FLAG_DESC 0x2 74 : : 75 : : /* 76 : : * Wrap counter bit shift in event suppression structure 77 : : * of packed ring. 78 : : */ 79 : : #define VRING_PACKED_EVENT_F_WRAP_CTR 15 80 : : 81 : : /* We support indirect buffer descriptors */ 82 : : #define VIRTIO_RING_F_INDIRECT_DESC 28 83 : : 84 : : /* The Guest publishes the used index for which it expects an interrupt 85 : : * at the end of the avail ring. Host should ignore the avail->flags field. */ 86 : : /* The Host publishes the avail index for which it expects a kick 87 : : * at the end of the used ring. Guest should ignore the used->flags field. */ 88 : : #define VIRTIO_RING_F_EVENT_IDX 29 89 : : 90 : : /* Virtio ring descriptors: 16 bytes. These can chain together via "next". */ 91 : : struct vring_desc { 92 : : /* Address (guest-physical). */ 93 : : __virtio64 addr; 94 : : /* Length. */ 95 : : __virtio32 len; 96 : : /* The flags as indicated above. */ 97 : : __virtio16 flags; 98 : : /* We chain unused descriptors via this, too */ 99 : : __virtio16 next; 100 : : }; 101 : : 102 : : struct vring_avail { 103 : : __virtio16 flags; 104 : : __virtio16 idx; 105 : : __virtio16 ring[]; 106 : : }; 107 : : 108 : : /* u32 is used here for ids for padding reasons. */ 109 : : struct vring_used_elem { 110 : : /* Index of start of used descriptor chain. */ 111 : : __virtio32 id; 112 : : /* Total length of the descriptor chain which was used (written to) */ 113 : : __virtio32 len; 114 : : }; 115 : : 116 : : struct vring_used { 117 : : __virtio16 flags; 118 : : __virtio16 idx; 119 : : struct vring_used_elem ring[]; 120 : : }; 121 : : 122 : : struct vring { 123 : : unsigned int num; 124 : : 125 : : struct vring_desc *desc; 126 : : 127 : : struct vring_avail *avail; 128 : : 129 : : struct vring_used *used; 130 : : }; 131 : : 132 : : /* Alignment requirements for vring elements. 133 : : * When using pre-virtio 1.0 layout, these fall out naturally. 134 : : */ 135 : : #define VRING_AVAIL_ALIGN_SIZE 2 136 : : #define VRING_USED_ALIGN_SIZE 4 137 : : #define VRING_DESC_ALIGN_SIZE 16 138 : : 139 : : /* The standard layout for the ring is a continuous chunk of memory which looks 140 : : * like this. We assume num is a power of 2. 141 : : * 142 : : * struct vring 143 : : * { 144 : : * The actual descriptors (16 bytes each) 145 : : * struct vring_desc desc[num]; 146 : : * 147 : : * A ring of available descriptor heads with free-running index. 148 : : * __virtio16 avail_flags; 149 : : * __virtio16 avail_idx; 150 : : * __virtio16 available[num]; 151 : : * __virtio16 used_event_idx; 152 : : * 153 : : * Padding to the next align boundary. 154 : : * char pad[]; 155 : : * 156 : : * A ring of used descriptor heads with free-running index. 157 : : * __virtio16 used_flags; 158 : : * __virtio16 used_idx; 159 : : * struct vring_used_elem used[num]; 160 : : * __virtio16 avail_event_idx; 161 : : * }; 162 : : */ 163 : : /* We publish the used event index at the end of the available ring, and vice 164 : : * versa. They are at the end for backwards compatibility. */ 165 : : #define vring_used_event(vr) ((vr)->avail->ring[(vr)->num]) 166 : : #define vring_avail_event(vr) (*(__virtio16 *)&(vr)->used->ring[(vr)->num]) 167 : : 168 : : static inline void 169 : 172 : vring_init(struct vring *vr, unsigned int num, void *p, 170 : : unsigned long align) 171 : : { 172 : 172 : vr->num = num; 173 : 172 : vr->desc = p; 174 : 172 : vr->avail = (struct vring_avail *)((char *)p + num * sizeof(struct vring_desc 175 : : )); 176 : 344 : vr->used = (void *)(((uintptr_t)&vr->avail->ring[num] + sizeof(__virtio16) 177 : 172 : + align - 1) & ~(align - 1)); 178 : 172 : } 179 : : 180 : : static inline unsigned 181 : 172 : vring_size(unsigned int num, unsigned long align) 182 : : { 183 : 172 : return ((sizeof(struct vring_desc) * num + sizeof(__virtio16) * (3 + num) 184 : 172 : + align - 1) & ~(align - 1)) 185 : 172 : + sizeof(__virtio16) * 3 + sizeof(struct vring_used_elem) * num; 186 : : } 187 : : 188 : : /* The following is used with USED_EVENT_IDX and AVAIL_EVENT_IDX */ 189 : : /* Assuming a given event_idx value from the other side, if 190 : : * we have just incremented index from old to new_idx, 191 : : * should we trigger an event? */ 192 : : static inline int 193 : 0 : vring_need_event(__u16 event_idx, __u16 new_idx, __u16 old) 194 : : { 195 : : /* Note: Xen has similar logic for notification hold-off 196 : : * in include/xen/interface/io/ring.h with req_event and req_prod 197 : : * corresponding to event_idx + 1 and new_idx respectively. 198 : : * Note also that req_event and req_prod in Xen start at 1, 199 : : * event indexes in virtio start at 0. */ 200 : 0 : return (__u16)(new_idx - event_idx - 1) < (__u16)(new_idx - old); 201 : : } 202 : : 203 : : struct vring_packed_desc_event { 204 : : /* Descriptor Ring Change Event Offset/Wrap Counter. */ 205 : : __le16 off_wrap; 206 : : /* Descriptor Ring Change Event Flags. */ 207 : : __le16 flags; 208 : : }; 209 : : 210 : : struct vring_packed_desc { 211 : : /* Buffer Address. */ 212 : : __le64 addr; 213 : : /* Buffer Length. */ 214 : : __le32 len; 215 : : /* Buffer ID. */ 216 : : __le16 id; 217 : : /* The flags depending on descriptor type. */ 218 : : __le16 flags; 219 : : }; 220 : : 221 : : #endif /* _LINUX_VIRTIO_RING_H */