Merge tag 'linux-kselftest-4.18-rc1-2' of git://git.kernel.org/pub/scm/linux/kernel...
[muen/linux.git] / include / linux / virtio_ring.h
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                 rmb();
39 }
40
41 static inline void virtio_wmb(bool weak_barriers)
42 {
43         if (weak_barriers)
44                 virt_wmb();
45         else
46                 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_ring_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 */