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
  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  */
  68 struct 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. */
  80 struct 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  */
  93 struct 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  */
 108 void vring_del_virtqueue(struct virtqueue *vq);
 109
 110 /* Filter out transport-specific feature bits. */
 111 void vring_transport_features(struct virtio_device *vdev);
 112
 113 irqreturn_t vring_interrupt(int irq, void *_vq);
 114 #endif /* _LINUX_VIRTIO_RING_H */