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 smp_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 #ifdef CONFIG_SMP
  25 static inline void virtio_mb(bool weak_barriers)
  26 {
  27         if (weak_barriers)
  28                 smp_mb();
  29         else
  30                 mb();
  31 }
  32
  33 static inline void virtio_rmb(bool weak_barriers)
  34 {
  35         if (weak_barriers)
  36                 smp_rmb();
  37         else
  38                 rmb();
  39 }
  40
  41 static inline void virtio_wmb(bool weak_barriers)
  42 {
  43         if (weak_barriers)
  44                 smp_wmb();
  45         else
  46                 wmb();
  47 }
  48 #else
  49 static inline void virtio_mb(bool weak_barriers)
  50 {
  51         mb();
  52 }
  53
  54 static inline void virtio_rmb(bool weak_barriers)
  55 {
  56         rmb();
  57 }
  58
  59 static inline void virtio_wmb(bool weak_barriers)
  60 {
  61         wmb();
  62 }
  63 #endif
  64
  65 struct virtio_device;
  66 struct virtqueue;
  67
  68 struct virtqueue *vring_new_virtqueue(unsigned int index,
  69                                       unsigned int num,
  70                                       unsigned int vring_align,
  71                                       struct virtio_device *vdev,
  72                                       bool weak_barriers,
  73                                       void *pages,
  74                                       bool (*notify)(struct virtqueue *vq),
  75                                       void (*callback)(struct virtqueue *vq),
  76                                       const char *name);
  77 void vring_del_virtqueue(struct virtqueue *vq);
  78 /* Filter out transport-specific feature bits. */
  79 void vring_transport_features(struct virtio_device *vdev);
  80
  81 irqreturn_t vring_interrupt(int irq, void *_vq);
  82 #endif /* _LINUX_VIRTIO_RING_H */