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

Hayato Ohhashi posted 1 patch 2 weeks ago
Failed in applying to current master (apply log)
arch/x86/xen/time.c | 1 +
1 file changed, 1 insertion(+)

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

Posted by Hayato Ohhashi 2 weeks ago
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


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

Posted by Boris Ostrovsky 2 weeks ago
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>