* [PATCH] x86/time: tsc_check_writability() may need to be run a second time
@ 2017-02-10 11:03 Jan Beulich
2017-02-10 11:05 ` Andrew Cooper
2017-02-10 11:11 ` Joao Martins
0 siblings, 2 replies; 5+ messages in thread
From: Jan Beulich @ 2017-02-10 11:03 UTC (permalink / raw)
To: xen-devel; +Cc: Andrew Cooper, Joao Martins
[-- Attachment #1: Type: text/plain, Size: 904 bytes --]
While we shouldn't remove its current invocation, we need to re-run it
for the case that the X86_FEATURE_TSC_RELIABLE feature flag has been
cleared, in order to avoid using the TSC rendezvous function in case
the TSC can't be written.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -1643,6 +1643,14 @@ static int __init verify_tsc_reliability
}
/*
+ * Re-run the TSC writability check if it didn't run to completion, as
+ * X86_FEATURE_TSC_RELIABLE may have been cleared by now. This is needed
+ * for determining which rendezvous function to use (below).
+ */
+ if ( !disable_tsc_sync )
+ tsc_check_writability();
+
+ /*
* While with constant-rate TSCs the scale factor can be shared, when TSCs
* are not marked as 'reliable', re-sync during rendezvous.
*/
[-- Attachment #2: x86-time-rerun-TSC-write-check.patch --]
[-- Type: text/plain, Size: 968 bytes --]
x86/time: tsc_check_writability() may need to be run a second time
While we shouldn't remove its current invocation, we need to re-run it
for the case that the X86_FEATURE_TSC_RELIABLE feature flag has been
cleared, in order to avoid using the TSC rendezvous function in case
the TSC can't be written.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -1643,6 +1643,14 @@ static int __init verify_tsc_reliability
}
/*
+ * Re-run the TSC writability check if it didn't run to completion, as
+ * X86_FEATURE_TSC_RELIABLE may have been cleared by now. This is needed
+ * for determining which rendezvous function to use (below).
+ */
+ if ( !disable_tsc_sync )
+ tsc_check_writability();
+
+ /*
* While with constant-rate TSCs the scale factor can be shared, when TSCs
* are not marked as 'reliable', re-sync during rendezvous.
*/
[-- Attachment #3: Type: text/plain, Size: 127 bytes --]
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] x86/time: tsc_check_writability() may need to be run a second time
2017-02-10 11:03 [PATCH] x86/time: tsc_check_writability() may need to be run a second time Jan Beulich
@ 2017-02-10 11:05 ` Andrew Cooper
2017-02-10 11:11 ` Joao Martins
1 sibling, 0 replies; 5+ messages in thread
From: Andrew Cooper @ 2017-02-10 11:05 UTC (permalink / raw)
To: Jan Beulich, xen-devel; +Cc: Joao Martins
On 10/02/17 11:03, Jan Beulich wrote:
> While we shouldn't remove its current invocation, we need to re-run it
> for the case that the X86_FEATURE_TSC_RELIABLE feature flag has been
> cleared, in order to avoid using the TSC rendezvous function in case
> the TSC can't be written.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] x86/time: tsc_check_writability() may need to be run a second time
2017-02-10 11:03 [PATCH] x86/time: tsc_check_writability() may need to be run a second time Jan Beulich
2017-02-10 11:05 ` Andrew Cooper
@ 2017-02-10 11:11 ` Joao Martins
2017-02-10 11:17 ` Andrew Cooper
1 sibling, 1 reply; 5+ messages in thread
From: Joao Martins @ 2017-02-10 11:11 UTC (permalink / raw)
To: Jan Beulich; +Cc: xen-devel, Andrew Cooper
On 02/10/2017 11:03 AM, Jan Beulich wrote:
> While we shouldn't remove its current invocation, we need to re-run it
> for the case that the X86_FEATURE_TSC_RELIABLE feature flag has been
> cleared, in order to avoid using the TSC rendezvous function in case
> the TSC can't be written.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
FWIW,
Reviewed-by: Joao Martins <joao.m.martins@oracle.com>
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] x86/time: tsc_check_writability() may need to be run a second time
2017-02-10 11:11 ` Joao Martins
@ 2017-02-10 11:17 ` Andrew Cooper
2017-02-10 12:08 ` Joao Martins
0 siblings, 1 reply; 5+ messages in thread
From: Andrew Cooper @ 2017-02-10 11:17 UTC (permalink / raw)
To: Joao Martins, Jan Beulich; +Cc: xen-devel
On 10/02/17 11:11, Joao Martins wrote:
> On 02/10/2017 11:03 AM, Jan Beulich wrote:
>> While we shouldn't remove its current invocation, we need to re-run it
>> for the case that the X86_FEATURE_TSC_RELIABLE feature flag has been
>> cleared, in order to avoid using the TSC rendezvous function in case
>> the TSC can't be written.
>>
>> Signed-off-by: Jan Beulich <jbeulich@suse.com>
> FWIW,
Independent reviews are always worth it. Please continue!
~Andrew
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] x86/time: tsc_check_writability() may need to be run a second time
2017-02-10 11:17 ` Andrew Cooper
@ 2017-02-10 12:08 ` Joao Martins
0 siblings, 0 replies; 5+ messages in thread
From: Joao Martins @ 2017-02-10 12:08 UTC (permalink / raw)
To: Andrew Cooper; +Cc: xen-devel, Jan Beulich
On 02/10/2017 11:17 AM, Andrew Cooper wrote:
> On 10/02/17 11:11, Joao Martins wrote:
>> On 02/10/2017 11:03 AM, Jan Beulich wrote:
>>> While we shouldn't remove its current invocation, we need to re-run it
>>> for the case that the X86_FEATURE_TSC_RELIABLE feature flag has been
>>> cleared, in order to avoid using the TSC rendezvous function in case
>>> the TSC can't be written.
>>>
>>> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>> FWIW,
>
> Independent reviews are always worth it. Please continue!
Nice, Thanks!
Joao
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2017-02-10 12:05 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2017-02-10 11:03 [PATCH] x86/time: tsc_check_writability() may need to be run a second time Jan Beulich
2017-02-10 11:05 ` Andrew Cooper
2017-02-10 11:11 ` Joao Martins
2017-02-10 11:17 ` Andrew Cooper
2017-02-10 12:08 ` Joao Martins
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).