virtio_ring: Update weak barriers to use dma_wmb/rmb

This change makes it so that instead of using smp_wmb/rmb which varies
depending on the kernel configuration we can can use dma_wmb/rmb which for
most architectures should be equal to or slightly more strict than
smp_wmb/rmb.

The advantage to this is that these barriers are available to uniprocessor
builds as well so the performance should improve under such a
configuration.

Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 4 insertions, 19 deletions

diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h
index 67e06fe18c03..8e50888a6d59 100644
--- a/include/linux/virtio_ring.h
+++ b/include/linux/virtio_ring.h
@@ -21,19 +21,20 @@
  * actually quite cheap.
  */
 
-#ifdef CONFIG_SMP
 static inline void virtio_mb(bool weak_barriers)
 {
+#ifdef CONFIG_SMP
         if (weak_barriers)
                 smp_mb();
         else
+#endif
                 mb();
 }
 
 static inline void virtio_rmb(bool weak_barriers)
 {
         if (weak_barriers)
-                smp_rmb();
+                dma_rmb();
         else
                 rmb();
 }
@@ -41,26 +42,10 @@ static inline void virtio_rmb(bool weak_barriers)
 static inline void virtio_wmb(bool weak_barriers)
 {
         if (weak_barriers)
-                smp_wmb();
+                dma_wmb();
         else
                 wmb();
 }
-#else
-static inline void virtio_mb(bool weak_barriers)
-{
-        mb();
-}
-
-static inline void virtio_rmb(bool weak_barriers)
-{
-        rmb();
-}
-
-static inline void virtio_wmb(bool weak_barriers)
-{
-        wmb();
-}
-#endif
 
 struct virtio_device;
 struct virtqueue;