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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 * Copyright Rusty Russell IBM Corporation 2007. */
11#include <linux/types.h>
12
13/* This marks a buffer as continuing via the next field. */
14#define VRING_DESC_F_NEXT 1
15/* This marks a buffer as write-only (otherwise read-only). */
16#define VRING_DESC_F_WRITE 2
17/* This means the buffer contains a list of buffer descriptors. */
18#define VRING_DESC_F_INDIRECT 4
19
20/* The Host uses this in used->flags to advise the Guest: don't kick me when
21 * you add a buffer. It's unreliable, so it's simply an optimization. Guest
22 * will still kick if it's out of buffers. */
23#define VRING_USED_F_NO_NOTIFY 1
24/* The Guest uses this in avail->flags to advise the Host: don't interrupt me
25 * when you consume a buffer. It's unreliable, so it's simply an
26 * optimization. */
27#define VRING_AVAIL_F_NO_INTERRUPT 1
28
29/* We support indirect buffer descriptors */
30#define VIRTIO_RING_F_INDIRECT_DESC 28
31
32/* Virtio ring descriptors: 16 bytes. These can chain together via "next". */
33struct vring_desc
34{
35 /* Address (guest-physical). */
36 __u64 addr;
37 /* Length. */
38 __u32 len;
39 /* The flags as indicated above. */
40 __u16 flags;
41 /* We chain unused descriptors via this, too */
42 __u16 next;
43};
44
45struct vring_avail
46{
47 __u16 flags;
48 __u16 idx;
49 __u16 ring[];
50};
51
52/* u32 is used here for ids for padding reasons. */
53struct vring_used_elem
54{
55 /* Index of start of used descriptor chain. */
56 __u32 id;
57 /* Total length of the descriptor chain which was used (written to) */
58 __u32 len;
59};
60
61struct vring_used
62{
63 __u16 flags;
64 __u16 idx;
65 struct vring_used_elem ring[];
66};
67
68struct vring {
69 unsigned int num;
70
71 struct vring_desc *desc;
72
73 struct vring_avail *avail;
74
75 struct vring_used *used;
76};
77
78/* The standard layout for the ring is a continuous chunk of memory which looks
79 * like this. We assume num is a power of 2.
80 *
81 * struct vring
82 * {
83 * // The actual descriptors (16 bytes each)
84 * struct vring_desc desc[num];
85 *
86 * // A ring of available descriptor heads with free-running index.
87 * __u16 avail_flags;
88 * __u16 avail_idx;
89 * __u16 available[num];
90 *
91 * // Padding to the next align boundary.
92 * char pad[];
93 *
94 * // A ring of used descriptor heads with free-running index.
95 * __u16 used_flags;
96 * __u16 used_idx;
97 * struct vring_used_elem used[num];
98 * };
99 */
100static inline void vring_init(struct vring *vr, unsigned int num, void *p,
101 unsigned long align)
102{
103 vr->num = num;
104 vr->desc = p;
105 vr->avail = p + num*sizeof(struct vring_desc);
106 vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + align-1)
107 & ~(align - 1));
108}
109
110static inline unsigned vring_size(unsigned int num, unsigned long align)
111{
112 return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (2 + num)
113 + align - 1) & ~(align - 1))
114 + sizeof(__u16) * 2 + sizeof(struct vring_used_elem) * num;
115}
116
117#ifdef __KERNEL__
118#include <linux/irqreturn.h>
119struct virtio_device;
120struct virtqueue;
121
122struct virtqueue *vring_new_virtqueue(unsigned int num,
123 unsigned int vring_align,
124 struct virtio_device *vdev,
125 void *pages,
126 void (*notify)(struct virtqueue *vq),
127 void (*callback)(struct virtqueue *vq),
128 const char *name);
129void vring_del_virtqueue(struct virtqueue *vq);
130/* Filter out transport-specific feature bits. */
131void vring_transport_features(struct virtio_device *vdev);
132
133irqreturn_t vring_interrupt(int irq, void *_vq);
134#endif /* __KERNEL__ */
135#endif /* _LINUX_VIRTIO_RING_H */