1 files changed, 14 insertions, 0 deletions
diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index d908a37bf3f3..904494b924c1 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -351,6 +351,20 @@ void __init kvmclock_init(void)
 	machine_ops.crash_shutdown  = kvm_crash_shutdown;
 #endif
 	kvm_get_preset_lpj();
+
+	/*
+	 * X86_FEATURE_NONSTOP_TSC is TSC runs at constant rate
+	 * with P/T states and does not stop in deep C-states.
+	 *
+	 * Invariant TSC exposed by host means kvmclock is not necessary:
+	 * can use TSC as clocksource.
+	 *
+	 */
+	if (boot_cpu_has(X86_FEATURE_CONSTANT_TSC) &&
+	    boot_cpu_has(X86_FEATURE_NONSTOP_TSC) &&
+	    !check_tsc_unstable())
+		kvm_clock.rating = 299;
+
 	clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
 	pv_info.name = "KVM";
 }