1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef _LINUX_VIRTIO_RING_H
3 #define _LINUX_VIRTIO_RING_H
4
5 #include <asm/barrier.h>
6 #include <linux/virtio.h>
7 #include <linux/irqreturn.h>
8 #include <uapi/linux/virtio_ring.h>
9
10 /*
11 * Barriers in virtio are tricky. Non-SMP virtio guests can't assume
12 * they're not on an SMP host system, so they need to assume real
13 * barriers. Non-SMP virtio hosts could skip the barriers, but does
14 * anyone care?
15 *
16 * For virtio_pci on SMP, we don't need to order with respect to MMIO
17 * accesses through relaxed memory I/O windows, so virt_mb() et al are
18 * sufficient.
19 *
20 * For using virtio to talk to real devices (eg. other heterogeneous
21 * CPUs) we do need real barriers. In theory, we could be using both
22 * kinds of virtio, so it's a runtime decision, and the branch is
23 * actually quite cheap.
24 */
25
virtio_mb(bool weak_barriers)26 static inline void virtio_mb(bool weak_barriers)
27 {
28 if (weak_barriers)
29 virt_mb();
30 else
31 mb();
32 }
33
virtio_rmb(bool weak_barriers)34 static inline void virtio_rmb(bool weak_barriers)
35 {
36 if (weak_barriers)
37 virt_rmb();
38 else
39 dma_rmb();
40 }
41
virtio_wmb(bool weak_barriers)42 static inline void virtio_wmb(bool weak_barriers)
43 {
44 if (weak_barriers)
45 virt_wmb();
46 else
47 dma_wmb();
48 }
49
50 #define virtio_store_mb(weak_barriers, p, v) \
51 do { \
52 if (weak_barriers) { \
53 virt_store_mb(*p, v); \
54 } else { \
55 WRITE_ONCE(*p, v); \
56 mb(); \
57 } \
58 } while (0) \
59
60 struct virtio_device;
61 struct virtqueue;
62 struct device;
63
64 /*
65 * Creates a virtqueue and allocates the descriptor ring. If
66 * may_reduce_num is set, then this may allocate a smaller ring than
67 * expected. The caller should query virtqueue_get_vring_size to learn
68 * the actual size of the ring.
69 */
70 struct virtqueue *vring_create_virtqueue(unsigned int index,
71 unsigned int num,
72 unsigned int vring_align,
73 struct virtio_device *vdev,
74 bool weak_barriers,
75 bool may_reduce_num,
76 bool ctx,
77 bool (*notify)(struct virtqueue *vq),
78 void (*callback)(struct virtqueue *vq),
79 const char *name);
80
81 /*
82 * Creates a virtqueue and allocates the descriptor ring with per
83 * virtqueue mapping operations.
84 */
85 struct virtqueue *vring_create_virtqueue_map(unsigned int index,
86 unsigned int num,
87 unsigned int vring_align,
88 struct virtio_device *vdev,
89 bool weak_barriers,
90 bool may_reduce_num,
91 bool ctx,
92 bool (*notify)(struct virtqueue *vq),
93 void (*callback)(struct virtqueue *vq),
94 const char *name,
95 union virtio_map map);
96
97 /*
98 * Creates a virtqueue with a standard layout but a caller-allocated
99 * ring.
100 */
101 struct virtqueue *vring_new_virtqueue(unsigned int index,
102 unsigned int num,
103 unsigned int vring_align,
104 struct virtio_device *vdev,
105 bool weak_barriers,
106 bool ctx,
107 void *pages,
108 bool (*notify)(struct virtqueue *vq),
109 void (*callback)(struct virtqueue *vq),
110 const char *name);
111
112 /*
113 * Destroys a virtqueue. If created with vring_create_virtqueue, this
114 * also frees the ring.
115 */
116 void vring_del_virtqueue(struct virtqueue *vq);
117
118 /* Filter out transport-specific feature bits. */
119 void vring_transport_features(struct virtio_device *vdev);
120
121 irqreturn_t vring_interrupt(int irq, void *_vq);
122
123 u32 vring_notification_data(struct virtqueue *_vq);
124 #endif /* _LINUX_VIRTIO_RING_H */
125