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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.
7 * This header is BSD licensed so anyone can use the definitions to implement
8 * compatible drivers/servers.
10 * Copyright Rusty Russell IBM Corporation 2007. */
11 #include <linux/types.h>
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
18 /* The Host uses this in used->flags to advise the Guest: don't kick me when
19 * you add a buffer. It's unreliable, so it's simply an optimization. Guest
20 * will still kick if it's out of buffers. */
21 #define VRING_USED_F_NO_NOTIFY 1
22 /* The Guest uses this in avail->flags to advise the Host: don't interrupt me
23 * when you consume a buffer. It's unreliable, so it's simply an
25 #define VRING_AVAIL_F_NO_INTERRUPT 1
27 /* Virtio ring descriptors: 16 bytes. These can chain together via "next". */
30 /* Address (guest-physical). */
34 /* The flags as indicated above. */
36 /* We chain unused descriptors via this, too */
47 /* u32 is used here for ids for padding reasons. */
48 struct vring_used_elem
50 /* Index of start of used descriptor chain. */
52 /* Total length of the descriptor chain which was used (written to) */
60 struct vring_used_elem ring
[];
66 struct vring_desc
*desc
;
68 struct vring_avail
*avail
;
70 struct vring_used
*used
;
73 /* The standard layout for the ring is a continuous chunk of memory which looks
74 * like this. We assume num is a power of 2.
78 * // The actual descriptors (16 bytes each)
79 * struct vring_desc desc[num];
81 * // A ring of available descriptor heads with free-running index.
84 * __u16 available[num];
86 * // Padding to the next align boundary.
89 * // A ring of used descriptor heads with free-running index.
92 * struct vring_used_elem used[num];
95 static inline void vring_init(struct vring
*vr
, unsigned int num
, void *p
,
100 vr
->avail
= p
+ num
*sizeof(struct vring_desc
);
101 vr
->used
= (void *)(((unsigned long)&vr
->avail
->ring
[num
] + align
-1)
105 static inline unsigned vring_size(unsigned int num
, unsigned long align
)
107 return ((sizeof(struct vring_desc
) * num
+ sizeof(__u16
) * (2 + num
)
108 + align
- 1) & ~(align
- 1))
109 + sizeof(__u16
) * 2 + sizeof(struct vring_used_elem
) * num
;
113 #include <linux/irqreturn.h>
114 struct virtio_device
;
117 struct virtqueue
*vring_new_virtqueue(unsigned int num
,
118 unsigned int vring_align
,
119 struct virtio_device
*vdev
,
121 void (*notify
)(struct virtqueue
*vq
),
122 void (*callback
)(struct virtqueue
*vq
));
123 void vring_del_virtqueue(struct virtqueue
*vq
);
124 /* Filter out transport-specific feature bits. */
125 void vring_transport_features(struct virtio_device
*vdev
);
127 irqreturn_t
vring_interrupt(int irq
, void *_vq
);
128 #endif /* __KERNEL__ */
129 #endif /* _LINUX_VIRTIO_RING_H */