GNU Linux-libre 6.9.2-gnu
[releases.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                 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 #define virtio_store_mb(weak_barriers, p, v) \
50 do { \
51         if (weak_barriers) { \
52                 virt_store_mb(*p, v); \
53         } else { \
54                 WRITE_ONCE(*p, v); \
55                 mb(); \
56         } \
57 } while (0) \
58
59 struct virtio_device;
60 struct virtqueue;
61 struct device;
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 /*
81  * Creates a virtqueue and allocates the descriptor ring with per
82  * virtqueue DMA device.
83  */
84 struct virtqueue *vring_create_virtqueue_dma(unsigned int index,
85                                              unsigned int num,
86                                              unsigned int vring_align,
87                                              struct virtio_device *vdev,
88                                              bool weak_barriers,
89                                              bool may_reduce_num,
90                                              bool ctx,
91                                              bool (*notify)(struct virtqueue *vq),
92                                              void (*callback)(struct virtqueue *vq),
93                                              const char *name,
94                                              struct device *dma_dev);
95
96 /*
97  * Creates a virtqueue with a standard layout but a caller-allocated
98  * ring.
99  */
100 struct virtqueue *vring_new_virtqueue(unsigned int index,
101                                       unsigned int num,
102                                       unsigned int vring_align,
103                                       struct virtio_device *vdev,
104                                       bool weak_barriers,
105                                       bool ctx,
106                                       void *pages,
107                                       bool (*notify)(struct virtqueue *vq),
108                                       void (*callback)(struct virtqueue *vq),
109                                       const char *name);
110
111 /*
112  * Destroys a virtqueue.  If created with vring_create_virtqueue, this
113  * also frees the ring.
114  */
115 void vring_del_virtqueue(struct virtqueue *vq);
116
117 /* Filter out transport-specific feature bits. */
118 void vring_transport_features(struct virtio_device *vdev);
119
120 irqreturn_t vring_interrupt(int irq, void *_vq);
121
122 u32 vring_notification_data(struct virtqueue *_vq);
123 #endif /* _LINUX_VIRTIO_RING_H */