diff mbox

[v2,30/32] virtio_ring: update weak barriers to use __smp_xxx

Message ID 1451572003-2440-31-git-send-email-mst@redhat.com (mailing list archive)
State Awaiting Upstream
Delegated to: Geert Uytterhoeven
Headers show

Commit Message

Michael S. Tsirkin Jan. 1, 2016, 9:39 a.m. UTC
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 __smp_XXX barriers do,
so switch to these instead of homegrown ifdef hacks.

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

Comments

Michael S. Tsirkin Jan. 1, 2016, 10:21 a.m. UTC | #1
On Fri, Jan 01, 2016 at 11:39:40AM +0200, Michael S. Tsirkin wrote:
> 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 __smp_XXX barriers do,
> so switch to these instead of homegrown ifdef hacks.
> 
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Alexander Duyck <alexander.duyck@gmail.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

The subject and commit log should say
virt_xxx and not __smp_xxx - I fixed this up in
my tree.

> ---
>  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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diff mbox

Patch

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;