4.17-stable review patch. If anyone has any objections, please let me know. ------------------ From: Peng Hao <peng.hao2@xxxxxxxxxx> [ Upstream commit e10f7805032365cc11c739a97f226ebb48aee042 ] 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: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Signed-off-by: Peng Hao <peng.hao2@xxxxxxxxxx> [Commit message rewritten. - Paolo] Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/kernel/kvmclock.c | 1 + 1 file changed, 1 insertion(+) --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -138,6 +138,7 @@ static unsigned long kvm_get_tsc_khz(voi 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; }
