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 * and lguest, 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 35 /* This marks a buffer as continuing via the next field. */ 36 #define VRING_DESC_F_NEXT 1 37 /* This marks a buffer as write-only (otherwise read-only). */ 38 #define VRING_DESC_F_WRITE 2 39 /* This means the buffer contains a list of buffer descriptors. */ 40 #define VRING_DESC_F_INDIRECT 4 41 42 /* The Host uses this in used->flags to advise the Guest: don't kick me when 43 * you add a buffer. It's unreliable, so it's simply an optimization. Guest 44 * will still kick if it's out of buffers. */ 45 #define VRING_USED_F_NO_NOTIFY 1 46 /* The Guest uses this in avail->flags to advise the Host: don't interrupt me 47 * when you consume a buffer. It's unreliable, so it's simply an 48 * optimization. */ 49 #define VRING_AVAIL_F_NO_INTERRUPT 1 50 51 /* We support indirect buffer descriptors */ 52 #define VIRTIO_RING_F_INDIRECT_DESC 28 53 54 /* The Guest publishes the used index for which it expects an interrupt 55 * at the end of the avail ring. Host should ignore the avail->flags field. */ 56 /* The Host publishes the avail index for which it expects a kick 57 * at the end of the used ring. Guest should ignore the used->flags field. */ 58 #define VIRTIO_RING_F_EVENT_IDX 29 59 60 /* Virtio ring descriptors: 16 bytes. These can chain together via "next". */ 61 struct vring_desc { 62 /* Address (guest-physical). */ 63 u64_t addr; 64 /* Length. */ 65 u32_t len; 66 /* The flags as indicated above. */ 67 u16_t flags; 68 /* We chain unused descriptors via this, too */ 69 u16_t next; 70 }; 71 72 struct vring_avail { 73 u16_t flags; 74 u16_t idx; 75 u16_t ring[]; 76 }; 77 78 /* u32 is used here for ids for padding reasons. */ 79 struct vring_used_elem { 80 /* Index of start of used descriptor chain. */ 81 u32_t id; 82 /* Total length of the descriptor chain which was used (written to) */ 83 u32_t len; 84 }; 85 86 struct vring_used { 87 u16_t flags; 88 u16_t idx; 89 struct vring_used_elem ring[]; 90 }; 91 92 struct vring { 93 unsigned int num; 94 95 struct vring_desc *desc; 96 97 struct vring_avail *avail; 98 99 struct vring_used *used; 100 }; 101 102 /* The standard layout for the ring is a continuous chunk of memory which looks 103 * like this. We assume num is a power of 2. 104 * 105 * struct vring 106 * { 107 * // The actual descriptors (16 bytes each) 108 * struct vring_desc desc[num]; 109 * 110 * // A ring of available descriptor heads with free-running index. 111 * u16_t avail_flags; 112 * u16_t avail_idx; 113 * u16_t available[num]; 114 * u16_t used_event_idx; 115 * 116 * // Padding to the next align boundary. 117 * char pad[]; 118 * 119 * // A ring of used descriptor heads with free-running index. 120 * u16_t used_flags; 121 * u16_t used_idx; 122 * struct vring_used_elem used[num]; 123 * u16_t avail_event_idx; 124 * }; 125 */ 126 /* We publish the used event index at the end of the available ring, and vice 127 * versa. They are at the end for backwards compatibility. */ 128 #define vring_used_event(vr) ((vr)->avail->ring[(vr)->num]) 129 #define vring_avail_event(vr) (*(u16_t *)&(vr)->used->ring[(vr)->num]) 130 131 static inline void vring_init(struct vring *vr, unsigned int num, void *p, 132 unsigned long align) 133 { 134 vr->num = num; 135 vr->desc = p; 136 vr->avail = p + num*sizeof(struct vring_desc); 137 vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + sizeof(u16_t) 138 + align-1) & ~(align - 1)); 139 } 140 141 static inline unsigned vring_size(unsigned int num, unsigned long align) 142 { 143 return ((sizeof(struct vring_desc) * num + sizeof(u16_t) * (3 + num) 144 + align - 1) & ~(align - 1)) 145 + sizeof(u16_t) * 3 + sizeof(struct vring_used_elem) * num; 146 } 147 148 #if 0 149 /* The following is used with USED_EVENT_IDX and AVAIL_EVENT_IDX */ 150 /* Assuming a given event_idx value from the other size, if 151 * we have just incremented index from old to new_idx, 152 * should we trigger an event? */ 153 static inline int vring_need_event(u16_t event_idx, u16_t new_idx, u16_t old) 154 { 155 /* Note: Xen has similar logic for notification hold-off 156 * in include/xen/interface/io/ring.h with req_event and req_prod 157 * corresponding to event_idx + 1 and new_idx respectively. 158 * Note also that req_event and req_prod in Xen start at 1, 159 * event indexes in virtio start at 0. */ 160 return (u16_t)(new_idx - event_idx - 1) < (u16_t)(new_idx - old); 161 } 162 163 #ifdef __KERNEL__ 164 #include <linux/irqreturn.h> 165 struct virtio_device; 166 struct virtqueue; 167 168 struct virtqueue *vring_new_virtqueue(unsigned int num, 169 unsigned int vring_align, 170 struct virtio_device *vdev, 171 bool weak_barriers, 172 void *pages, 173 void (*notify)(struct virtqueue *vq), 174 void (*callback)(struct virtqueue *vq), 175 const char *name); 176 void vring_del_virtqueue(struct virtqueue *vq); 177 /* Filter out transport-specific feature bits. */ 178 void vring_transport_features(struct virtio_device *vdev); 179 180 irqreturn_t vring_interrupt(int irq, void *_vq); 181 #endif /* __KERNEL__ */ 182 #endif /* 0 */ 183 #endif /* _LINUX_VIRTIO_RING_H */ 184