[PATCH v3 39/41] xen/events: use virt_xxx barriers
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- To: linux-kernel@xxxxxxxxxxxxxxx
- Subject: [PATCH v3 39/41] xen/events: use virt_xxx barriers
- From: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
- Date: Sun, 10 Jan 2016 16:21:56 +0200
- Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>, Arnd Bergmann <arnd@xxxxxxxx>, linux-arch@xxxxxxxxxxxxxxx, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx>, virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx, Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Joe Perches <joe@xxxxxxxxxxx>, David Miller <davem@xxxxxxxxxxxxx>, linux-ia64@xxxxxxxxxxxxxxx, linuxppc-dev@xxxxxxxxxxxxxxxx, linux-s390@xxxxxxxxxxxxxxx, sparclinux@xxxxxxxxxxxxxxx, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, linux-metag@xxxxxxxxxxxxxxx, linux-mips@xxxxxxxxxxxxxx, x86@xxxxxxxxxx, user-mode-linux-devel@xxxxxxxxxxxxxxxxxxxxx, adi-buildroot-devel@xxxxxxxxxxxxxxxxxxxxx, linux-sh@xxxxxxxxxxxxxxx, linux-xtensa@xxxxxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx, David Vrabel <david.vrabel@xxxxxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Julien Grall <julien.grall@xxxxxxxxxx>, Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>, Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>, Wei Liu <wei.liu2@xxxxxxxxxx>
- In-reply-to: <1452426622-4471-1-git-send-email-mst@redhat.com>
- List-id: <linux-ia64.vger.kernel.org>
- References: <1452426622-4471-1-git-send-email-mst@redhat.com>
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 <david.vrabel@xxxxxxxxxx>
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
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 <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];
}
--
MST
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