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 struct virtqueue *vring_new_virtqueue(unsigned int index,
  63                                       unsigned int num,
  64                                       unsigned int vring_align,
  65                                       struct virtio_device *vdev,
  66                                       bool weak_barriers,
  67                                       void *pages,
  68                                       bool (*notify)(struct virtqueue *vq),
  69                                       void (*callback)(struct virtqueue *vq),
  70                                       const char *name);
  71 void vring_del_virtqueue(struct virtqueue *vq);
  72 /* Filter out transport-specific feature bits. */
  73 void vring_transport_features(struct virtio_device *vdev);
  74
  75 irqreturn_t vring_interrupt(int irq, void *_vq);
  76 #endif /* _LINUX_VIRTIO_RING_H */