Commit e10f7805 authored by Peng Hao's avatar Peng Hao Committed by Paolo Bonzini

kvmclock: fix TSC calibration for nested guests

Inside a nested guest, access to hardware can be slow enough that
tsc_read_refs always return ULLONG_MAX, causing tsc_refine_calibration_work
to be called periodically and the nested guest to spend a lot of time
reading the ACPI timer.

However, if the TSC frequency is available from the pvclock page,
we can just set X86_FEATURE_TSC_KNOWN_FREQ and avoid the recalibration.
'refine' operation.
Suggested-by: default avatarPeter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarPeng Hao <peng.hao2@zte.com.cn>
[Commit message rewritten. - Paolo]
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 2307af1c
......@@ -138,6 +138,7 @@ static unsigned long kvm_get_tsc_khz(void)
src = &hv_clock[cpu].pvti;
tsc_khz = pvclock_tsc_khz(src);
put_cpu();
setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
return tsc_khz;
}
......
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