[Xen-devel] [PATCH v3 30/41] virtio_ring: update weak barriers to use virt_xxx

["Michael S. Tsirkin" <mst@xxxxxxxxxx>]

virtio ring uses smp_wmb on SMP and wmb on !SMP,
the reason for the later being that it might be
talking to another kernel on the same SMP machine.

This is exactly what virt_xxx barriers do,
so switch to these instead of homegrown ifdef hacks.

Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Alexander Duyck <alexander.duyck@xxxxxxxxx>
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
 include/linux/virtio_ring.h | 25 ++++---------------------
 1 file changed, 4 insertions(+), 21 deletions(-)

diff --git a/include/linux/virtio_ring.h b/include/linux/virtio_ring.h
index 67e06fe..f3fa55b 100644
--- a/include/linux/virtio_ring.h
+++ b/include/linux/virtio_ring.h
@@ -12,7 +12,7 @@
  * anyone care?
  *
  * For virtio_pci on SMP, we don't need to order with respect to MMIO
- * accesses through relaxed memory I/O windows, so smp_mb() et al are
+ * accesses through relaxed memory I/O windows, so virt_mb() et al are
  * sufficient.
  *
  * For using virtio to talk to real devices (eg. other heterogeneous
@@ -21,11 +21,10 @@
  * actually quite cheap.
  */
 
-#ifdef CONFIG_SMP
 static inline void virtio_mb(bool weak_barriers)
 {
        if (weak_barriers)
-               smp_mb();
+               virt_mb();
        else
                mb();
 }
@@ -33,7 +32,7 @@ static inline void virtio_mb(bool weak_barriers)
 static inline void virtio_rmb(bool weak_barriers)
 {
        if (weak_barriers)
-               smp_rmb();
+               virt_rmb();
        else
                rmb();
 }
@@ -41,26 +40,10 @@ static inline void virtio_rmb(bool weak_barriers)
 static inline void virtio_wmb(bool weak_barriers)
 {
        if (weak_barriers)
-               smp_wmb();
+               virt_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;
-- 
MST


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