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 #include <xdc/std.h>
36 /* This marks a buffer as continuing via the next field. */
37 #define VRING_DESC_F_NEXT 1
38 /* This marks a buffer as write-only (otherwise read-only). */
39 #define VRING_DESC_F_WRITE 2
41 /* The Host uses this in used->flags to advise the Guest: don't kick me when
42 * you add a buffer. It's unreliable, so it's simply an optimization. Guest
43 * will still kick if it's out of buffers. */
44 #define VRING_USED_F_NO_NOTIFY 1
45 /* The Guest uses this in avail->flags to advise the Host: don't interrupt me
46 * when you consume a buffer. It's unreliable, so it's simply an
47 * optimization. */
48 #define VRING_AVAIL_F_NO_INTERRUPT 1
50 /* Virtio ring descriptors: 16 bytes. These can chain together via "next". */
51 struct vring_desc
52 {
53 /* Address (guest-physical). */
54 UInt32 addr;
56 UInt32 padding; /* Because 64 bits is originally used for addr */
58 /* Length. */
59 UInt32 len;
60 /* The flags as indicated above. */ //Optional for now!
61 UInt16 flags;
62 /* We chain unused descriptors via this, too */
63 UInt16 next;
64 };
66 struct vring_avail
67 {
68 UInt16 flags;
69 UInt16 idx;
70 UInt16 ring[256];
71 };
73 /* u32 is used here for ids for padding reasons. */
74 struct vring_used_elem
75 {
76 /* Index of start of used descriptor chain. */
77 UInt32 id;
78 /* Total length of the descriptor chain which was used (written to) */
79 UInt32 len;
80 };
82 struct vring_used
83 {
84 UInt16 flags;
85 UInt16 idx;
86 struct vring_used_elem ring[256];
87 };
89 struct vring {
90 unsigned int num;
92 struct vring_desc *desc;
94 struct vring_avail *avail;
96 struct vring_used *used;
97 };
99 /*
100 * When you boot you have to add all the buffers to your own A8
101 * - Call add buf repeatedly
102 * - When we take the buffer from the available list, you should have the pointer in the descriptor address
103 *
104 */
106 /* The standard layout for the ring is a continuous chunk of memory which looks
107 * like this. We assume num is a power of 2.
108 *
109 * struct vring
110 * {
111 * // The actual descriptors (16 bytes each)
112 * struct vring_desc desc[num];
113 *
114 * // A ring of available descriptor heads with free-running index.
115 * UInt16 avail_flags;
116 * UInt16 avail_idx;
117 * UInt16 available[num];
118 *
119 * // Padding to the next page boundary.
120 * char pad[];
121 *
122 * // A ring of used descriptor heads with free-running index.
123 * UInt16 used_flags;
124 * UInt16 used_idx;
125 * struct vring_used_elem used[num];
126 * };
127 */
128 static inline void vring_init(struct vring *vr, unsigned int num, void *p,
129 unsigned long pagesize)
130 {
131 vr->num = num;
132 vr->desc = p;
133 vr->avail = (struct vring_avail *)
134 ((unsigned)p + (num * sizeof(struct vring_desc)));
135 vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + pagesize-1)
136 & ~(pagesize - 1));
137 }
139 static inline unsigned vring_size(unsigned int num, unsigned long pagesize)
140 {
141 return ((sizeof(struct vring_desc) * num + sizeof(UInt16) * (2 + num)
142 + pagesize - 1) & ~(pagesize - 1))
143 + sizeof(UInt16) * 2 + sizeof(struct vring_used_elem) * num;
144 }
146 #ifdef __KERNEL__
147 #include <linux/interrupt.h>
148 struct virtio_device;
149 struct virtqueue;
151 struct virtqueue *vring_new_virtqueue(unsigned int num,
152 struct virtio_device *vdev,
153 void *pages,
154 void (*notify)(struct virtqueue *vq),
155 void (*callback)(struct virtqueue *vq));
157 void vring_del_virtqueue(struct virtqueue *vq);
158 /* Filter out transport-specific feature bits. */
159 void vring_transport_features(struct virtio_device *vdev);
161 irqreturn_t vring_interrupt(int irq, void *_vq);
162 #endif /* __KERNEL__ */
163 #endif /* _LINUX_VIRTIO_RING_H */