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". */
33 struct vring_desc {
34 /* Address (guest-physical). */
35 __u64 addr;
36 /* Length. */
37 __u32 len;
38 /* The flags as indicated above. */
39 __u16 flags;
40 /* We chain unused descriptors via this, too */
41 __u16 next;
42 };
43
44 struct vring_avail {
45 __u16 flags;
46 __u16 idx;
47 __u16 ring[];
48 };
49
50 /* u32 is used here for ids for padding reasons. */
51 struct vring_used_elem {
52 /* Index of start of used descriptor chain. */
53 __u32 id;
54 /* Total length of the descriptor chain which was used (written to) */
55 __u32 len;
56 };
57
58 struct vring_used {
59 __u16 flags;
60 __u16 idx;
61 struct vring_used_elem ring[];
62 };
63
64 struct vring {
65 unsigned int num;
66
67 struct vring_desc *desc;
68
69 struct vring_avail *avail;
70
71 struct vring_used *used;
72 };
73
74 /* The standard layout for the ring is a continuous chunk of memory which looks
75 * like this. We assume num is a power of 2.
76 *
77 * struct vring
78 * {
79 * // The actual descriptors (16 bytes each)
80 * struct vring_desc desc[num];
81 *
82 * // A ring of available descriptor heads with free-running index.
83 * __u16 avail_flags;
84 * __u16 avail_idx;
85 * __u16 available[num];
86 *
87 * // Padding to the next align boundary.
88 * char pad[];
89 *
90 * // A ring of used descriptor heads with free-running index.
91 * __u16 used_flags;
92 * __u16 used_idx;
93 * struct vring_used_elem used[num];
94 * };
95 */
96 static inline void vring_init(struct vring *vr, unsigned int num, void *p,
97 unsigned long align)
98 {
99 vr->num = num;
100 vr->desc = p;
101 vr->avail = p + num*sizeof(struct vring_desc);
102 vr->used = (void *)(((unsigned long)&vr->avail->ring[num] + align-1)
103 & ~(align - 1));
104 }
105
106 static inline unsigned vring_size(unsigned int num, unsigned long align)
107 {
108 return ((sizeof(struct vring_desc) * num + sizeof(__u16) * (2 + num)
109 + align - 1) & ~(align - 1))
110 + sizeof(__u16) * 2 + sizeof(struct vring_used_elem) * num;
111 }
112
113 #ifdef __KERNEL__
114 #include <linux/irqreturn.h>
115 struct virtio_device;
116 struct virtqueue;
117
118 struct virtqueue *vring_new_virtqueue(unsigned int num,
119 unsigned int vring_align,
120 struct virtio_device *vdev,
121 void *pages,
122 void (*notify)(struct virtqueue *vq),
123 void (*callback)(struct virtqueue *vq),
124 const char *name);
125 void vring_del_virtqueue(struct virtqueue *vq);
126 /* Filter out transport-specific feature bits. */
127 void vring_transport_features(struct virtio_device *vdev);
128
129 irqreturn_t vring_interrupt(int irq, void *_vq);
130 #endif /* __KERNEL__ */
131 #endif /* _LINUX_VIRTIO_RING_H */
132
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