Re: [PATCH v3 39/41] xen/events: use virt_xxx barriers

[David Vrabel]

On 10/01/16 14:21, Michael S. Tsirkin wrote:
> drivers/xen/events/events_fifo.c uses rmb() to communicate with the
> other side.
> 
> For guests compiled with CONFIG_SMP, smp_rmb would be sufficient, so
> rmb() here is only needed if a non-SMP guest runs on an SMP host.
> 
> Switch to the virt_rmb barrier which serves this exact purpose.
> 
> Pull in asm/barrier.h here to make sure the file is self-contained.
> 
> Suggested-by: David Vrabel 
> Signed-off-by: Michael S. Tsirkin 

Acked-by: David Vrabel 

David
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[PATCH v3 39/41] xen/events: use virt_xxx barriers

[Michael S. Tsirkin]

drivers/xen/events/events_fifo.c uses rmb() to communicate with the
other side.

For guests compiled with CONFIG_SMP, smp_rmb would be sufficient, so
rmb() here is only needed if a non-SMP guest runs on an SMP host.

Switch to the virt_rmb barrier which serves this exact purpose.

Pull in asm/barrier.h here to make sure the file is self-contained.

Suggested-by: David Vrabel 
Signed-off-by: Michael S. Tsirkin 
---
 drivers/xen/events/events_fifo.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/events/events_fifo.c b/drivers/xen/events/events_fifo.c
index 96a1b8d..eff2b88 100644
--- a/drivers/xen/events/events_fifo.c
+++ b/drivers/xen/events/events_fifo.c
@@ -41,6 +41,7 @@
 #include 
 #include 
 
+#include 
 #include 
 #include 
 #include 
@@ -296,7 +297,7 @@ static void consume_one_event(unsigned cpu,
 * control block.
 */
if (head == 0) {
-   rmb(); /* Ensure word is up-to-date before reading head. */
+   virt_rmb(); /* Ensure word is up-to-date before reading head. */
head = control_block->head[priority];
}
 
-- 
MST

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