From e10f7805032365cc11c739a97f226ebb48aee042 Mon Sep 17 00:00:00 2001 From: Peng Hao Date: Sat, 14 Jul 2018 23:28:29 +0800 Subject: [PATCH] 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: Peter Zijlstra Signed-off-by: Peng Hao [Commit message rewritten. - Paolo] Signed-off-by: Paolo Bonzini --- arch/x86/kernel/kvmclock.c | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c index d79a18b4cf9d..4c53d12ca933 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -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; } -- 2.30.2