include/linux/virtio_ring.h

   1 #ifndef _LINUX_VIRTIO_RING_H
   2 #define _LINUX_VIRTIO_RING_H
   3
   4 #include <asm/barrier.h>
   5 #include <linux/irqreturn.h>
   6 #include <uapi/linux/virtio_ring.h>
   7
   8 /*
   9  * Barriers in virtio are tricky.  Non-SMP virtio guests can't assume
  10  * they're not on an SMP host system, so they need to assume real
  11  * barriers.  Non-SMP virtio hosts could skip the barriers, but does
  12  * anyone care?
  13  *
  14  * For virtio_pci on SMP, we don't need to order with respect to MMIO
  15  * accesses through relaxed memory I/O windows, so virt_mb() et al are
  16  * sufficient.
  17  *
  18  * For using virtio to talk to real devices (eg. other heterogeneous
  19  * CPUs) we do need real barriers.  In theory, we could be using both
  20  * kinds of virtio, so it's a runtime decision, and the branch is
  21  * actually quite cheap.
  22  */
  23
  24 static inline void virtio_mb(bool weak_barriers)
  25 {
  26         if (weak_barriers)
  27                 virt_mb();
  28         else
  29                 mb();
  30 }
  31
  32 static inline void virtio_rmb(bool weak_barriers)
  33 {
  34         if (weak_barriers)
  35                 virt_rmb();
  36         else
  37                 rmb();
  38 }
  39
  40 static inline void virtio_wmb(bool weak_barriers)
  41 {
  42         if (weak_barriers)
  43                 virt_wmb();
  44         else
  45                 wmb();
  46 }
  47
  48 static inline void virtio_store_mb(bool weak_barriers,
  49                                    __virtio16 *p, __virtio16 v)
  50 {
  51         if (weak_barriers) {
  52                 virt_store_mb(*p, v);
  53         } else {
  54                 WRITE_ONCE(*p, v);
  55                 mb();
  56         }
  57 }
  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_ring_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 (*notify)(struct virtqueue *vq),
  75                                          void (*callback)(struct virtqueue *vq),
  76                                          const char *name);
  77
  78 /* Creates a virtqueue with a custom layout. */
  79 struct virtqueue *__vring_new_virtqueue(unsigned int index,
  80                                         struct vring vring,
  81                                         struct virtio_device *vdev,
  82                                         bool weak_barriers,
  83                                         bool (*notify)(struct virtqueue *),
  84                                         void (*callback)(struct virtqueue *),
  85                                         const char *name);
  86
  87 /*
  88  * Creates a virtqueue with a standard layout but a caller-allocated
  89  * ring.
  90  */
  91 struct virtqueue *vring_new_virtqueue(unsigned int index,
  92                                       unsigned int num,
  93                                       unsigned int vring_align,
  94                                       struct virtio_device *vdev,
  95                                       bool weak_barriers,
  96                                       void *pages,
  97                                       bool (*notify)(struct virtqueue *vq),
  98                                       void (*callback)(struct virtqueue *vq),
  99                                       const char *name);
 100
 101 /*
 102  * Destroys a virtqueue.  If created with vring_create_virtqueue, this
 103  * also frees the ring.
 104  */
 105 void vring_del_virtqueue(struct virtqueue *vq);
 106
 107 /* Filter out transport-specific feature bits. */
 108 void vring_transport_features(struct virtio_device *vdev);
 109
 110 irqreturn_t vring_interrupt(int irq, void *_vq);
 111 #endif /* _LINUX_VIRTIO_RING_H */