Re: [PATCH 7/7] xen/evtchn: read producer index only once

2021-02-08 Thread Jürgen Groß
On 08.02.21 13:23, Jan Beulich wrote: On 08.02.2021 13:15, Jürgen Groß wrote: On 08.02.21 12:54, Jan Beulich wrote: On 08.02.2021 11:59, Jürgen Groß wrote: On 08.02.21 11:51, Jan Beulich wrote: On 08.02.2021 11:41, Jürgen Groß wrote: On 08.02.21 10:48, Jan Beulich wrote: On 06.02.2021 11:49

Re: [PATCH 7/7] xen/evtchn: read producer index only once

2021-02-08 Thread Jan Beulich
On 08.02.2021 13:15, Jürgen Groß wrote: > On 08.02.21 12:54, Jan Beulich wrote: >> On 08.02.2021 11:59, Jürgen Groß wrote: >>> On 08.02.21 11:51, Jan Beulich wrote: On 08.02.2021 11:41, Jürgen Groß wrote: > On 08.02.21 10:48, Jan Beulich wrote: >> On 06.02.2021 11:49, Juergen Gross wro

Re: [PATCH 7/7] xen/evtchn: read producer index only once

2021-02-08 Thread Jürgen Groß
On 08.02.21 12:54, Jan Beulich wrote: On 08.02.2021 11:59, Jürgen Groß wrote: On 08.02.21 11:51, Jan Beulich wrote: On 08.02.2021 11:41, Jürgen Groß wrote: On 08.02.21 10:48, Jan Beulich wrote: On 06.02.2021 11:49, Juergen Gross wrote: In evtchn_read() use READ_ONCE() for reading the produce

Re: [PATCH 7/7] xen/evtchn: read producer index only once

2021-02-08 Thread Julien Grall
Hi Juergen, On 08/02/2021 11:48, Jürgen Groß wrote: On 08.02.21 12:40, Julien Grall wrote: On 06/02/2021 10:49, Juergen Gross wrote: In evtchn_read() use READ_ONCE() for reading the producer index in order to avoid the compiler generating multiple accesses. Signed-off-by: Juergen Gross ---

Re: [PATCH 7/7] xen/evtchn: read producer index only once

2021-02-08 Thread Jan Beulich
On 08.02.2021 11:59, Jürgen Groß wrote: > On 08.02.21 11:51, Jan Beulich wrote: >> On 08.02.2021 11:41, Jürgen Groß wrote: >>> On 08.02.21 10:48, Jan Beulich wrote: On 06.02.2021 11:49, Juergen Gross wrote: > In evtchn_read() use READ_ONCE() for reading the producer index in > order to

Re: [PATCH 7/7] xen/evtchn: read producer index only once

2021-02-08 Thread Julien Grall
On 08/02/2021 10:59, Jürgen Groß wrote: On 08.02.21 11:51, Jan Beulich wrote: Yes, but I don't see an urgent need to fix that, as there would be thousands of accesses in the kernel needing a fix. A compiler tearing a naturally aligned access into multiple memory accesses would be rejected as b

Re: [PATCH 7/7] xen/evtchn: read producer index only once

2021-02-08 Thread Jürgen Groß
On 08.02.21 12:40, Julien Grall wrote: On 06/02/2021 10:49, Juergen Gross wrote: In evtchn_read() use READ_ONCE() for reading the producer index in order to avoid the compiler generating multiple accesses. Signed-off-by: Juergen Gross ---   drivers/xen/evtchn.c | 2 +-   1 file changed, 1 ins

Re: [PATCH 7/7] xen/evtchn: read producer index only once

2021-02-08 Thread Julien Grall
On 06/02/2021 10:49, Juergen Gross wrote: In evtchn_read() use READ_ONCE() for reading the producer index in order to avoid the compiler generating multiple accesses. Signed-off-by: Juergen Gross --- drivers/xen/evtchn.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/

Re: [PATCH 7/7] xen/evtchn: read producer index only once

2021-02-08 Thread Jürgen Groß
On 08.02.21 11:51, Jan Beulich wrote: On 08.02.2021 11:41, Jürgen Groß wrote: On 08.02.21 10:48, Jan Beulich wrote: On 06.02.2021 11:49, Juergen Gross wrote: In evtchn_read() use READ_ONCE() for reading the producer index in order to avoid the compiler generating multiple accesses. Signed-off

Re: [PATCH 7/7] xen/evtchn: read producer index only once

2021-02-08 Thread Jan Beulich
On 08.02.2021 11:41, Jürgen Groß wrote: > On 08.02.21 10:48, Jan Beulich wrote: >> On 06.02.2021 11:49, Juergen Gross wrote: >>> In evtchn_read() use READ_ONCE() for reading the producer index in >>> order to avoid the compiler generating multiple accesses. >>> >>> Signed-off-by: Juergen Gross >>>

Re: [PATCH 7/7] xen/evtchn: read producer index only once

2021-02-08 Thread Jürgen Groß
On 08.02.21 10:48, Jan Beulich wrote: On 06.02.2021 11:49, Juergen Gross wrote: In evtchn_read() use READ_ONCE() for reading the producer index in order to avoid the compiler generating multiple accesses. Signed-off-by: Juergen Gross --- drivers/xen/evtchn.c | 2 +- 1 file changed, 1 insert

Re: [PATCH 7/7] xen/evtchn: read producer index only once

2021-02-08 Thread Jan Beulich
On 06.02.2021 11:49, Juergen Gross wrote: > In evtchn_read() use READ_ONCE() for reading the producer index in > order to avoid the compiler generating multiple accesses. > > Signed-off-by: Juergen Gross > --- > drivers/xen/evtchn.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > di

[PATCH 7/7] xen/evtchn: read producer index only once

2021-02-06 Thread Juergen Gross
In evtchn_read() use READ_ONCE() for reading the producer index in order to avoid the compiler generating multiple accesses. Signed-off-by: Juergen Gross --- drivers/xen/evtchn.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/xen/evtchn.c b/drivers/xen/evtchn.c index