4.14-stable review patch. If anyone has any objections, please let me know.
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From: Peng Hao peng.hao2@zte.com.cn
[ 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@infradead.org Signed-off-by: Peng Hao peng.hao2@zte.com.cn [Commit message rewritten. - Paolo] Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/kernel/kvmclock.c | 1 + 1 file changed, 1 insertion(+)
--- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -143,6 +143,7 @@ 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; }