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/irqreturn.h>
7 #include <uapi/linux/virtio_ring.h>
8
9 /*
10 * Barriers in virtio are tricky. Non-SMP virtio guests can't assume
11 * they're not on an SMP host system, so they need to assume real
12 * barriers. Non-SMP virtio hosts could skip the barriers, but does
13 * anyone care?
14 *
15 * For virtio_pci on SMP, we don't need to order with respect to MMIO
16 * accesses through relaxed memory I/O windows, so virt_mb() et al are
17 * sufficient.
18 *
19 * For using virtio to talk to real devices (eg. other heterogeneous
20 * CPUs) we do need real barriers. In theory, we could be using both
21 * kinds of virtio, so it's a runtime decision, and the branch is
22 * actually quite cheap.
23 */
24
25 static inline void virtio_mb(bool weak_barriers)
26 {
27 if (weak_barriers)
28 virt_mb();
29 else
30 mb();
31 }
32
33 static inline void virtio_rmb(bool weak_barriers)
34 {
35 if (weak_barriers)
36 virt_rmb();
37 else
38 dma_rmb();
39 }
40
41 static inline void virtio_wmb(bool weak_barriers)
42 {
43 if (weak_barriers)
44 virt_wmb();
45 else
46 dma_wmb();
47 }
48
49 static inline void virtio_store_mb(bool weak_barriers,
50 __virtio16 *p, __virtio16 v)
51 {
52 if (weak_barriers) {
53 virt_store_mb(*p, v);
54 } else {
55 WRITE_ONCE(*p, v);
56 mb();
57 }
58 }
59
60 struct virtio_device;
61 struct virtqueue;
62
63 /*
64 * Creates a virtqueue and allocates the descriptor ring. If
65 * may_reduce_num is set, then this may allocate a smaller ring than
66 * expected. The caller should query virtqueue_get_vring_size to learn
67 * the actual size of the ring.
68 */
69 struct virtqueue *vring_create_virtqueue(unsigned int index,
70 unsigned int num,
71 unsigned int vring_align,
72 struct virtio_device *vdev,
73 bool weak_barriers,
74 bool may_reduce_num,
75 bool ctx,
76 bool (*notify)(struct virtqueue *vq),
77 void (*callback)(struct virtqueue *vq),
78 const char *name);
79
80 /* Creates a virtqueue with a custom layout. */
81 struct virtqueue *__vring_new_virtqueue(unsigned int index,
82 struct vring vring,
83 struct virtio_device *vdev,
84 bool weak_barriers,
85 bool ctx,
86 bool (*notify)(struct virtqueue *),
87 void (*callback)(struct virtqueue *),
88 const char *name);
89
90 /*
91 * Creates a virtqueue with a standard layout but a caller-allocated
92 * ring.
93 */
94 struct virtqueue *vring_new_virtqueue(unsigned int index,
95 unsigned int num,
96 unsigned int vring_align,
97 struct virtio_device *vdev,
98 bool weak_barriers,
99 bool ctx,
100 void *pages,
101 bool (*notify)(struct virtqueue *vq),
102 void (*callback)(struct virtqueue *vq),
103 const char *name);
104
105 /*
106 * Destroys a virtqueue. If created with vring_create_virtqueue, this
107 * also frees the ring.
108 */
109 void vring_del_virtqueue(struct virtqueue *vq);
110
111 /* Filter out transport-specific feature bits. */
112 void vring_transport_features(struct virtio_device *vdev);
113
114 irqreturn_t vring_interrupt(int irq, void *_vq);
115 #endif /* _LINUX_VIRTIO_RING_H */