LXR linux/include/linux/virtio

   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;
  61
  62/*
  63 * Creates a virtqueue and allocates the descriptor ring.  If
  64 * may_reduce_num is set, then this may allocate a smaller ring than
  65 * expected.  The caller should query virtqueue_get_vring_size to learn
  66 * the actual size of the ring.
  67 */
  68struct virtqueue *vring_create_virtqueue(unsigned int index,
  69                                         unsigned int num,
  70                                         unsigned int vring_align,
  71                                         struct virtio_device *vdev,
  72                                         bool weak_barriers,
  73                                         bool may_reduce_num,
  74                                         bool ctx,
  75                                         bool (*notify)(struct virtqueue *vq),
  76                                         void (*callback)(struct virtqueue *vq),
  77                                         const char *name);
  78
  79/* Creates a virtqueue with a custom layout. */
  80struct virtqueue *__vring_new_virtqueue(unsigned int index,
  81                                        struct vring vring,
  82                                        struct virtio_device *vdev,
  83                                        bool weak_barriers,
  84                                        bool ctx,
  85                                        bool (*notify)(struct virtqueue *),
  86                                        void (*callback)(struct virtqueue *),
  87                                        const char *name);
  88
  89/*
  90 * Creates a virtqueue with a standard layout but a caller-allocated
  91 * ring.
  92 */
  93struct virtqueue *vring_new_virtqueue(unsigned int index,
  94                                      unsigned int num,
  95                                      unsigned int vring_align,
  96                                      struct virtio_device *vdev,
  97                                      bool weak_barriers,
  98                                      bool ctx,
  99                                      void *pages,
 100                                      bool (*notify)(struct virtqueue *vq),
 101                                      void (*callback)(struct virtqueue *vq),
 102                                      const char *name);
 103
 104/*
 105 * Destroys a virtqueue.  If created with vring_create_virtqueue, this
 106 * also frees the ring.
 107 */
 108void vring_del_virtqueue(struct virtqueue *vq);
 109
 110/* Filter out transport-specific feature bits. */
 111void vring_transport_features(struct virtio_device *vdev);
 112
 113irqreturn_t vring_interrupt(int irq, void *_vq);
 114#endif /* _LINUX_VIRTIO_RING_H */
 115