* [PATCH] x86/xen/time: set the X86_FEATURE_TSC_KNOWN_FREQ flag in xen_tsc_khz()
@ 2020-07-21 16:12 Hayato Ohhashi
2020-07-21 23:33 ` Boris Ostrovsky
2020-07-25 13:53 ` [tip: x86/timers] x86/xen/time: Set " tip-bot2 for Hayato Ohhashi
0 siblings, 2 replies; 3+ messages in thread
From: Hayato Ohhashi @ 2020-07-21 16:12 UTC (permalink / raw)
To: tglx, mingo, bp, x86
Cc: xen-devel, linux-kernel, boris.ostrovsky, jgross, sstabellini,
Hayato Ohhashi
If the TSC frequency is known from the pvclock page,
the TSC frequency does not need to be recalibrated.
We can avoid recalibration by setting X86_FEATURE_TSC_KNOWN_FREQ.
Signed-off-by: Hayato Ohhashi <o8@vmm.dev>
---
arch/x86/xen/time.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index c8897aad13cd..91f5b330dcc6 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -39,6 +39,7 @@ static unsigned long xen_tsc_khz(void)
struct pvclock_vcpu_time_info *info =
&HYPERVISOR_shared_info->vcpu_info[0].time;
+ setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
return pvclock_tsc_khz(info);
}
--
2.23.3
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] x86/xen/time: set the X86_FEATURE_TSC_KNOWN_FREQ flag in xen_tsc_khz()
2020-07-21 16:12 [PATCH] x86/xen/time: set the X86_FEATURE_TSC_KNOWN_FREQ flag in xen_tsc_khz() Hayato Ohhashi
@ 2020-07-21 23:33 ` Boris Ostrovsky
2020-07-25 13:53 ` [tip: x86/timers] x86/xen/time: Set " tip-bot2 for Hayato Ohhashi
1 sibling, 0 replies; 3+ messages in thread
From: Boris Ostrovsky @ 2020-07-21 23:33 UTC (permalink / raw)
To: Hayato Ohhashi, tglx, mingo, bp, x86
Cc: xen-devel, linux-kernel, jgross, sstabellini
On 7/21/20 12:12 PM, Hayato Ohhashi wrote:
> If the TSC frequency is known from the pvclock page,
> the TSC frequency does not need to be recalibrated.
> We can avoid recalibration by setting X86_FEATURE_TSC_KNOWN_FREQ.
>
> Signed-off-by: Hayato Ohhashi <o8@vmm.dev>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
^ permalink raw reply [flat|nested] 3+ messages in thread
* [tip: x86/timers] x86/xen/time: Set the X86_FEATURE_TSC_KNOWN_FREQ flag in xen_tsc_khz()
2020-07-21 16:12 [PATCH] x86/xen/time: set the X86_FEATURE_TSC_KNOWN_FREQ flag in xen_tsc_khz() Hayato Ohhashi
2020-07-21 23:33 ` Boris Ostrovsky
@ 2020-07-25 13:53 ` tip-bot2 for Hayato Ohhashi
1 sibling, 0 replies; 3+ messages in thread
From: tip-bot2 for Hayato Ohhashi @ 2020-07-25 13:53 UTC (permalink / raw)
To: linux-tip-commits; +Cc: Hayato Ohhashi, Ingo Molnar, Boris Ostrovsky, x86, LKML
The following commit has been merged into the x86/timers branch of tip:
Commit-ID: 898ec52d2ba05915aaedcdb21bff2e944c883cb8
Gitweb: https://git.kernel.org/tip/898ec52d2ba05915aaedcdb21bff2e944c883cb8
Author: Hayato Ohhashi <o8@vmm.dev>
AuthorDate: Tue, 21 Jul 2020 16:12:31
Committer: Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 25 Jul 2020 15:49:41 +02:00
x86/xen/time: Set the X86_FEATURE_TSC_KNOWN_FREQ flag in xen_tsc_khz()
If the TSC frequency is known from the pvclock page,
the TSC frequency does not need to be recalibrated.
We can avoid recalibration by setting X86_FEATURE_TSC_KNOWN_FREQ.
Signed-off-by: Hayato Ohhashi <o8@vmm.dev>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Link: https://lore.kernel.org/r/20200721161231.6019-1-o8@vmm.dev
---
arch/x86/xen/time.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index c8897aa..91f5b33 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -39,6 +39,7 @@ static unsigned long xen_tsc_khz(void)
struct pvclock_vcpu_time_info *info =
&HYPERVISOR_shared_info->vcpu_info[0].time;
+ setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
return pvclock_tsc_khz(info);
}
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-07-21 16:12 [PATCH] x86/xen/time: set the X86_FEATURE_TSC_KNOWN_FREQ flag in xen_tsc_khz() Hayato Ohhashi
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2020-07-25 13:53 ` [tip: x86/timers] x86/xen/time: Set " tip-bot2 for Hayato Ohhashi
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