include/linux/virtio_ring.h

   1 #ifndef _LINUX_VIRTIO_RING_H
   2 #define _LINUX_VIRTIO_RING_H
   3
   4 #include <linux/irqreturn.h>
   5 #include <uapi/linux/virtio_ring.h>
   6
   7 /*
   8  * Barriers in virtio are tricky.  Non-SMP virtio guests can't assume
   9  * they're not on an SMP host system, so they need to assume real
  10  * barriers.  Non-SMP virtio hosts could skip the barriers, but does
  11  * anyone care?
  12  *
  13  * For virtio_pci on SMP, we don't need to order with respect to MMIO
  14  * accesses through relaxed memory I/O windows, so smp_mb() et al are
  15  * sufficient.
  16  *
  17  * For using virtio to talk to real devices (eg. other heterogeneous
  18  * CPUs) we do need real barriers.  In theory, we could be using both
  19  * kinds of virtio, so it's a runtime decision, and the branch is
  20  * actually quite cheap.
  21  */
  22
  23 #ifdef CONFIG_SMP
  24 static inline void virtio_mb(bool weak_barriers)
  25 {
  26         if (weak_barriers)
  27                 smp_mb();
  28         else
  29                 mb();
  30 }
  31
  32 static inline void virtio_rmb(bool weak_barriers)
  33 {
  34         if (weak_barriers)
  35                 smp_rmb();
  36         else
  37                 rmb();
  38 }
  39
  40 static inline void virtio_wmb(bool weak_barriers)
  41 {
  42         if (weak_barriers)
  43                 smp_wmb();
  44         else
  45                 wmb();
  46 }
  47 #else
  48 static inline void virtio_mb(bool weak_barriers)
  49 {
  50         mb();
  51 }
  52
  53 static inline void virtio_rmb(bool weak_barriers)
  54 {
  55         rmb();
  56 }
  57
  58 static inline void virtio_wmb(bool weak_barriers)
  59 {
  60         wmb();
  61 }
  62 #endif
  63
  64 struct virtio_device;
  65 struct virtqueue;
  66
  67 struct virtqueue *vring_new_virtqueue(unsigned int index,
  68                                       unsigned int num,
  69                                       unsigned int vring_align,
  70                                       struct virtio_device *vdev,
  71                                       bool weak_barriers,
  72                                       void *pages,
  73                                       void (*notify)(struct virtqueue *vq),
  74                                       void (*callback)(struct virtqueue *vq),
  75                                       const char *name);
  76 void vring_del_virtqueue(struct virtqueue *vq);
  77 /* Filter out transport-specific feature bits. */
  78 void vring_transport_features(struct virtio_device *vdev);
  79
  80 irqreturn_t vring_interrupt(int irq, void *_vq);
  81 #endif /* _LINUX_VIRTIO_RING_H */