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xen/events: use virt_xxx barriers

Browse source 
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 <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>
Acked-by: David Vrabel <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
This commit is contained in:
Michael S. Tsirkin 2015-12-27 18:02:16 +02:00
commit 234927540e
1 changed files with 2 additions and 1 deletions
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3
drivers/xen/events/events_fifo.c
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@ -41,6 +41,7 @@
#include <linux/percpu.h>
#include <linux/cpu.h>
#include <asm/barrier.h>
#include <asm/sync_bitops.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/hypervisor.h>
@ -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];
}