xref: /linux/include/linux/virtio_ring.h (revision 1ac731c529cd4d6adbce134754b51ff7d822b145)
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 
virtio_mb(bool weak_barriers)25 static inline void virtio_mb(bool weak_barriers)
26 {
27 	if (weak_barriers)
28 		virt_mb();
29 	else
30 		mb();
31 }
32 
virtio_rmb(bool weak_barriers)33 static inline void virtio_rmb(bool weak_barriers)
34 {
35 	if (weak_barriers)
36 		virt_rmb();
37 	else
38 		dma_rmb();
39 }
40 
virtio_wmb(bool weak_barriers)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 */
124