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
25static inline void virtio_mb(bool weak_barriers)
26{
27	if (weak_barriers)
28		virt_mb();
29	else
30		mb();
31}
32
33static inline void virtio_rmb(bool weak_barriers)
34{
35	if (weak_barriers)
36		virt_rmb();
37	else
38		dma_rmb();
39}
40
41static 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) \
50do { \
51	if (weak_barriers) { \
52		virt_store_mb(*p, v); \
53	} else { \
54		WRITE_ONCE(*p, v); \
55		mb(); \
56	} \
57} while (0) \
58
59struct virtio_device;
60struct virtqueue;
61struct 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 */
69struct 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 */
84struct 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 */
100struct 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 */
115void vring_del_virtqueue(struct virtqueue *vq);
116
117/* Filter out transport-specific feature bits. */
118void vring_transport_features(struct virtio_device *vdev);
119
120irqreturn_t vring_interrupt(int irq, void *_vq);
121
122u32 vring_notification_data(struct virtqueue *_vq);
123#endif /* _LINUX_VIRTIO_RING_H */
124