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1 : : #ifndef _UAPI_LINUX_VIRTIO_RING_H 2 : : #define _UAPI_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'' AND 22 : : * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 : : * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 : : * ARE DISCLAIMED. IN NO EVENT SHALL IBM OR CONTRIBUTORS BE LIABLE 25 : : * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 : : * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 : : * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 : : * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 : : * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 : : * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 : : * SUCH DAMAGE. 32 : : * 33 : : * Copyright Rusty Russell IBM Corporation 2007. */ 34 : : #ifndef __KERNEL__ 35 : : #include <stdint.h> 36 : : #endif 37 : : #include <linux/types.h> 38 : : #include <linux/virtio_types.h> 39 : : 40 : : /* This marks a buffer as continuing via the next field. */ 41 : : #define VRING_DESC_F_NEXT 1 42 : : /* This marks a buffer as write-only (otherwise read-only). */ 43 : : #define VRING_DESC_F_WRITE 2 44 : : /* This means the buffer contains a list of buffer descriptors. */ 45 : : #define VRING_DESC_F_INDIRECT 4 46 : : 47 : : /* 48 : : * Mark a descriptor as available or used in packed ring. 49 : : * Notice: they are defined as shifts instead of shifted values. 50 : : */ 51 : : #define VRING_PACKED_DESC_F_AVAIL 7 52 : : #define VRING_PACKED_DESC_F_USED 15 53 : : 54 : : /* The Host uses this in used->flags to advise the Guest: don't kick me when 55 : : * you add a buffer. It's unreliable, so it's simply an optimization. Guest 56 : : * will still kick if it's out of buffers. */ 57 : : #define VRING_USED_F_NO_NOTIFY 1 58 : : /* The Guest uses this in avail->flags to advise the Host: don't interrupt me 59 : : * when you consume a buffer. It's unreliable, so it's simply an 60 : : * optimization. */ 61 : : #define VRING_AVAIL_F_NO_INTERRUPT 1 62 : : 63 : : /* Enable events in packed ring. */ 64 : : #define VRING_PACKED_EVENT_FLAG_ENABLE 0x0 65 : : /* Disable events in packed ring. */ 66 : : #define VRING_PACKED_EVENT_FLAG_DISABLE 0x1 67 : : /* 68 : : * Enable events for a specific descriptor in packed ring. 69 : : * (as specified by Descriptor Ring Change Event Offset/Wrap Counter). 70 : : * Only valid if VIRTIO_RING_F_EVENT_IDX has been negotiated. 71 : : */ 72 : : #define VRING_PACKED_EVENT_FLAG_DESC 0x2 73 : : 74 : : /* 75 : : * Wrap counter bit shift in event suppression structure 76 : : * of packed ring. 77 : : */ 78 : : #define VRING_PACKED_EVENT_F_WRAP_CTR 15 79 : : 80 : : /* We support indirect buffer descriptors */ 81 : : #define VIRTIO_RING_F_INDIRECT_DESC 28 82 : : 83 : : /* The Guest publishes the used index for which it expects an interrupt 84 : : * at the end of the avail ring. Host should ignore the avail->flags field. */ 85 : : /* The Host publishes the avail index for which it expects a kick 86 : : * at the end of the used ring. Guest should ignore the used->flags field. */ 87 : : #define VIRTIO_RING_F_EVENT_IDX 29 88 : : 89 : : /* Virtio ring descriptors: 16 bytes. These can chain together via "next". */ 90 : : struct vring_desc { 91 : : /* Address (guest-physical). */ 92 : : __virtio64 addr; 93 : : /* Length. */ 94 : : __virtio32 len; 95 : : /* The flags as indicated above. */ 96 : : __virtio16 flags; 97 : : /* We chain unused descriptors via this, too */ 98 : : __virtio16 next; 99 : : }; 100 : : 101 : : struct vring_avail { 102 : : __virtio16 flags; 103 : : __virtio16 idx; 104 : : __virtio16 ring[]; 105 : : }; 106 : : 107 : : /* u32 is used here for ids for padding reasons. */ 108 : : struct vring_used_elem { 109 : : /* Index of start of used descriptor chain. */ 110 : : __virtio32 id; 111 : : /* Total length of the descriptor chain which was used (written to) */ 112 : : __virtio32 len; 113 : : }; 114 : : 115 : : struct vring_used { 116 : : __virtio16 flags; 117 : : __virtio16 idx; 118 : : struct vring_used_elem ring[]; 119 : : }; 120 : : 121 : : struct vring { 122 : : unsigned int num; 123 : : 124 : : struct vring_desc *desc; 125 : : 126 : : struct vring_avail *avail; 127 : : 128 : : struct vring_used *used; 129 : : }; 130 : : 131 : : /* Alignment requirements for vring elements. 132 : : * When using pre-virtio 1.0 layout, these fall out naturally. 133 : : */ 134 : : #define VRING_AVAIL_ALIGN_SIZE 2 135 : : #define VRING_USED_ALIGN_SIZE 4 136 : : #define VRING_DESC_ALIGN_SIZE 16 137 : : 138 : : /* The standard layout for the ring is a continuous chunk of memory which looks 139 : : * like this. We assume num is a power of 2. 140 : : * 141 : : * struct vring 142 : : * { 143 : : * // The actual descriptors (16 bytes each) 144 : : * struct vring_desc desc[num]; 145 : : * 146 : : * // A ring of available descriptor heads with free-running index. 147 : : * __virtio16 avail_flags; 148 : : * __virtio16 avail_idx; 149 : : * __virtio16 available[num]; 150 : : * __virtio16 used_event_idx; 151 : : * 152 : : * // Padding to the next align boundary. 153 : : * char pad[]; 154 : : * 155 : : * // A ring of used descriptor heads with free-running index. 156 : : * __virtio16 used_flags; 157 : : * __virtio16 used_idx; 158 : : * struct vring_used_elem used[num]; 159 : : * __virtio16 avail_event_idx; 160 : : * }; 161 : : */ 162 : : /* We publish the used event index at the end of the available ring, and vice 163 : : * versa. They are at the end for backwards compatibility. */ 164 : : #define vring_used_event(vr) ((vr)->avail->ring[(vr)->num]) 165 : : #define vring_avail_event(vr) (*(__virtio16 *)&(vr)->used->ring[(vr)->num]) 166 : : 167 : 0 : static inline void vring_init(struct vring *vr, unsigned int num, void *p, 168 : : unsigned long align) 169 : : { 170 : 0 : vr->num = num; 171 : 0 : vr->desc = p; 172 : 0 : vr->avail = (struct vring_avail *)((char *)p + num * sizeof(struct vring_desc)); 173 : 0 : vr->used = (void *)(((uintptr_t)&vr->avail->ring[num] + sizeof(__virtio16) 174 : 0 : + align-1) & ~(align - 1)); 175 : : } 176 : : 177 : 0 : static inline unsigned vring_size(unsigned int num, unsigned long align) 178 : : { 179 : 0 : return ((sizeof(struct vring_desc) * num + sizeof(__virtio16) * (3 + num) 180 : 0 : + align - 1) & ~(align - 1)) 181 [ # # ]: 0 : + sizeof(__virtio16) * 3 + sizeof(struct vring_used_elem) * num; 182 : : } 183 : : 184 : : /* The following is used with USED_EVENT_IDX and AVAIL_EVENT_IDX */ 185 : : /* Assuming a given event_idx value from the other side, if 186 : : * we have just incremented index from old to new_idx, 187 : : * should we trigger an event? */ 188 : 0 : static inline int vring_need_event(__u16 event_idx, __u16 new_idx, __u16 old) 189 : : { 190 : : /* Note: Xen has similar logic for notification hold-off 191 : : * in include/xen/interface/io/ring.h with req_event and req_prod 192 : : * corresponding to event_idx + 1 and new_idx respectively. 193 : : * Note also that req_event and req_prod in Xen start at 1, 194 : : * event indexes in virtio start at 0. */ 195 : 0 : return (__u16)(new_idx - event_idx - 1) < (__u16)(new_idx - old); 196 : : } 197 : : 198 : : struct vring_packed_desc_event { 199 : : /* Descriptor Ring Change Event Offset/Wrap Counter. */ 200 : : __le16 off_wrap; 201 : : /* Descriptor Ring Change Event Flags. */ 202 : : __le16 flags; 203 : : }; 204 : : 205 : : struct vring_packed_desc { 206 : : /* Buffer Address. */ 207 : : __le64 addr; 208 : : /* Buffer Length. */ 209 : : __le32 len; 210 : : /* Buffer ID. */ 211 : : __le16 id; 212 : : /* The flags depending on descriptor type. */ 213 : : __le16 flags; 214 : : }; 215 : : 216 : : #endif /* _UAPI_LINUX_VIRTIO_RING_H */