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