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
vring_init(struct vring * vr,unsigned int num,void * p,unsigned long align)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 = (void *)((char *)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
vring_size(unsigned int num,unsigned long align)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