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.
7 * This header is BSD licensed so anyone can use the definitions to implement
8 * compatible drivers/servers.
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
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
33 * Copyright Rusty Russell IBM Corporation 2007. */
34 #include <linux/types.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
40 /* This means the buffer contains a list of buffer descriptors. */
41 #define VRING_DESC_F_INDIRECT 4
43 /* The Host uses this in used->flags to advise the Guest: don't kick me when
44 * you add a buffer. It's unreliable, so it's simply an optimization. Guest
45 * will still kick if it's out of buffers. */
46 #define VRING_USED_F_NO_NOTIFY 1
47 /* The Guest uses this in avail->flags to advise the Host: don't interrupt me
48 * when you consume a buffer. It's unreliable, so it's simply an
50 #define VRING_AVAIL_F_NO_INTERRUPT 1
52 /* We support indirect buffer descriptors */
53 #define VIRTIO_RING_F_INDIRECT_DESC 28
55 /* Virtio ring descriptors: 16 bytes. These can chain together via "next". */
57 /* Address (guest-physical). */
61 /* The flags as indicated above. */
63 /* We chain unused descriptors via this, too */
73 /* u32 is used here for ids for padding reasons. */
74 struct vring_used_elem {
75 /* Index of start of used descriptor chain. */
77 /* Total length of the descriptor chain which was used (written to) */
84 struct vring_used_elem ring[];
90 struct vring_desc *desc;
92 struct vring_avail *avail;
94 struct vring_used *used;
97 /* The standard layout for the ring is a continuous chunk of memory which looks
98 * like this. We assume num is a power of 2.
102 * // The actual descriptors (16 bytes each)
103 * struct vring_desc desc[num];
105 * // A ring of available descriptor heads with free-running index.
108 * __u16 available[num];
110 * // Padding to the next align boundary.
113 * // A ring of used descriptor heads with free-running index.
116 * struct vring_used_elem used[num];
119 static inline void vring_init(struct vring *vr, unsigned int num, void *p,
124 vr->avail = p + num*sizeof(struct vring_desc);
125 vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + align-1)
129 static inline unsigned vring_size(unsigned int num, unsigned long align)
131 return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (2 + num)
132 + align - 1) & ~(align - 1))
133 + sizeof(__u16) * 2 + sizeof(struct vring_used_elem) * num;
137 #include <linux/irqreturn.h>
138 struct virtio_device;
141 struct virtqueue *vring_new_virtqueue(unsigned int num,
142 unsigned int vring_align,
143 struct virtio_device *vdev,
145 void (*notify)(struct virtqueue *vq),
146 void (*callback)(struct virtqueue *vq),
148 void vring_del_virtqueue(struct virtqueue *vq);
149 /* Filter out transport-specific feature bits. */
150 void vring_transport_features(struct virtio_device *vdev);
152 irqreturn_t vring_interrupt(int irq, void *_vq);
153 #endif /* __KERNEL__ */
154 #endif /* _LINUX_VIRTIO_RING_H */