Re: [PATCH] x86/xen/time: set the X86_FEATURE_TSC_KNOWN_FREQ flag in xen_tsc_khz()

2020-07-21 Thread Boris Ostrovsky 
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 


Reviewed-by: Boris Ostrovsky

[PATCH] x86/xen/time: set the X86_FEATURE_TSC_KNOWN_FREQ flag in xen_tsc_khz()

2020-07-21 Thread 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 
---
 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 =
_shared_info->vcpu_info[0].time;
 
+   setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
return pvclock_tsc_khz(info);
 }
 
-- 
2.23.3