* [PATCH] xen/events: use virt_xxx barriers
@ 2016-01-04 11:46 Michael S. Tsirkin
2016-01-04 11:47 ` David Vrabel
` (3 more replies)
0 siblings, 4 replies; 6+ messages in thread
From: Michael S. Tsirkin @ 2016-01-04 11:46 UTC (permalink / raw)
To: linux-kernel
Cc: David Vrabel, Konrad Rzeszutek Wilk, Boris Ostrovsky,
Julien Grall, Stefano Stabellini, Ross Lagerwall, Wei Liu,
xen-devel
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@citrix.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
This is on top of my series:
arch: barrier cleanup + barriers for virt
and will be included in v3 of the series.
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
^ permalink raw reply related [flat|nested] 6+ messages in thread* Re: [PATCH] xen/events: use virt_xxx barriers
2016-01-04 11:46 [PATCH] xen/events: use virt_xxx barriers Michael S. Tsirkin
@ 2016-01-04 11:47 ` David Vrabel
2016-01-04 11:47 ` David Vrabel
` (2 subsequent siblings)
3 siblings, 0 replies; 6+ messages in thread
From: David Vrabel @ 2016-01-04 11:47 UTC (permalink / raw)
To: Michael S. Tsirkin, linux-kernel
Cc: Wei Liu, Julien Grall, Ross Lagerwall, Stefano Stabellini,
xen-devel, Boris Ostrovsky
On 04/01/16 11:46, 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.
Thanks!
Acked-by: David Vrabel <david.vrabel@citrix.com>
David
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] xen/events: use virt_xxx barriers
2016-01-04 11:46 [PATCH] xen/events: use virt_xxx barriers Michael S. Tsirkin
2016-01-04 11:47 ` David Vrabel
@ 2016-01-04 11:47 ` David Vrabel
2016-01-04 11:56 ` kbuild test robot
2016-01-04 11:56 ` kbuild test robot
3 siblings, 0 replies; 6+ messages in thread
From: David Vrabel @ 2016-01-04 11:47 UTC (permalink / raw)
To: Michael S. Tsirkin, linux-kernel
Cc: Konrad Rzeszutek Wilk, Boris Ostrovsky, Julien Grall,
Stefano Stabellini, Ross Lagerwall, Wei Liu, xen-devel
On 04/01/16 11:46, 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.
Thanks!
Acked-by: David Vrabel <david.vrabel@citrix.com>
David
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] xen/events: use virt_xxx barriers
2016-01-04 11:46 [PATCH] xen/events: use virt_xxx barriers Michael S. Tsirkin
2016-01-04 11:47 ` David Vrabel
2016-01-04 11:47 ` David Vrabel
@ 2016-01-04 11:56 ` kbuild test robot
2016-01-04 11:56 ` kbuild test robot
3 siblings, 0 replies; 6+ messages in thread
From: kbuild test robot @ 2016-01-04 11:56 UTC (permalink / raw)
To: Michael S. Tsirkin
Cc: kbuild-all, linux-kernel, David Vrabel, Konrad Rzeszutek Wilk,
Boris Ostrovsky, Julien Grall, Stefano Stabellini, Ross Lagerwall,
Wei Liu, xen-devel
[-- Attachment #1: Type: text/plain, Size: 1336 bytes --]
Hi Michael,
[auto build test ERROR on v4.4-rc8]
[also build test ERROR on next-20151231]
[if your patch is applied to the wrong git tree, please drop us a note to help improving the system]
url: https://github.com/0day-ci/linux/commits/Michael-S-Tsirkin/xen-events-use-virt_xxx-barriers/20160104-194916
config: x86_64-randconfig-x008-01040711 (attached as .config)
reproduce:
# save the attached .config to linux build tree
make ARCH=x86_64
All errors (new ones prefixed by >>):
drivers/xen/events/events_fifo.c: In function 'consume_one_event':
>> drivers/xen/events/events_fifo.c:300:3: error: implicit declaration of function 'virt_rmb' [-Werror=implicit-function-declaration]
virt_rmb(); /* Ensure word is up-to-date before reading head. */
^
cc1: some warnings being treated as errors
vim +/virt_rmb +300 drivers/xen/events/events_fifo.c
294
295 /*
296 * Reached the tail last time? Read the new HEAD from the
297 * control block.
298 */
299 if (head == 0) {
> 300 virt_rmb(); /* Ensure word is up-to-date before reading head. */
301 head = control_block->head[priority];
302 }
303
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
[-- Attachment #2: .config.gz --]
[-- Type: application/octet-stream, Size: 21830 bytes --]
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] xen/events: use virt_xxx barriers
2016-01-04 11:46 [PATCH] xen/events: use virt_xxx barriers Michael S. Tsirkin
` (2 preceding siblings ...)
2016-01-04 11:56 ` kbuild test robot
@ 2016-01-04 11:56 ` kbuild test robot
3 siblings, 0 replies; 6+ messages in thread
From: kbuild test robot @ 2016-01-04 11:56 UTC (permalink / raw)
To: Michael S. Tsirkin
Cc: Wei Liu, linux-kernel, Julien Grall, Ross Lagerwall,
Stefano Stabellini, David Vrabel, xen-devel, Boris Ostrovsky,
kbuild-all
[-- Attachment #1: Type: text/plain, Size: 1336 bytes --]
Hi Michael,
[auto build test ERROR on v4.4-rc8]
[also build test ERROR on next-20151231]
[if your patch is applied to the wrong git tree, please drop us a note to help improving the system]
url: https://github.com/0day-ci/linux/commits/Michael-S-Tsirkin/xen-events-use-virt_xxx-barriers/20160104-194916
config: x86_64-randconfig-x008-01040711 (attached as .config)
reproduce:
# save the attached .config to linux build tree
make ARCH=x86_64
All errors (new ones prefixed by >>):
drivers/xen/events/events_fifo.c: In function 'consume_one_event':
>> drivers/xen/events/events_fifo.c:300:3: error: implicit declaration of function 'virt_rmb' [-Werror=implicit-function-declaration]
virt_rmb(); /* Ensure word is up-to-date before reading head. */
^
cc1: some warnings being treated as errors
vim +/virt_rmb +300 drivers/xen/events/events_fifo.c
294
295 /*
296 * Reached the tail last time? Read the new HEAD from the
297 * control block.
298 */
299 if (head == 0) {
> 300 virt_rmb(); /* Ensure word is up-to-date before reading head. */
301 head = control_block->head[priority];
302 }
303
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
[-- Attachment #2: .config.gz --]
[-- Type: application/octet-stream, Size: 21830 bytes --]
[-- Attachment #3: Type: text/plain, Size: 126 bytes --]
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel
^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH] xen/events: use virt_xxx barriers
@ 2016-01-04 11:46 Michael S. Tsirkin
0 siblings, 0 replies; 6+ messages in thread
From: Michael S. Tsirkin @ 2016-01-04 11:46 UTC (permalink / raw)
To: linux-kernel
Cc: Wei Liu, Julien Grall, Ross Lagerwall, Stefano Stabellini,
David Vrabel, xen-devel, Boris Ostrovsky
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@citrix.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
This is on top of my series:
arch: barrier cleanup + barriers for virt
and will be included in v3 of the series.
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
^ permalink raw reply related [flat|nested] 6+ messages in thread
end of thread, other threads:[~2016-01-04 11:57 UTC | newest]
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2016-01-04 11:46 [PATCH] xen/events: use virt_xxx barriers Michael S. Tsirkin
2016-01-04 11:47 ` David Vrabel
2016-01-04 11:47 ` David Vrabel
2016-01-04 11:56 ` kbuild test robot
2016-01-04 11:56 ` kbuild test robot
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2016-01-04 11:46 Michael S. Tsirkin
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