X-Git-Url: http://git.osdn.net/view?a=blobdiff_plain;f=arch%2Fx86%2Fkvm%2Flapic.c;h=b5cd8465d44f6cb99a9ae705cf2f44f3c310a1ac;hb=b357bf6023a948cf6a9472f07a1b0caac0e4f8e8;hp=776391cf69a5196ae0fb33a6abbb496fc167f2fa;hpb=766d3571d8e50d3a73b77043dc632226f9e6b389;p=tomoyo%2Ftomoyo-test1.git

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 776391cf69a5..b5cd8465d44f 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1522,11 +1522,23 @@ static bool set_target_expiration(struct kvm_lapic *apic)
 
 static void advance_periodic_target_expiration(struct kvm_lapic *apic)
 {
-	apic->lapic_timer.tscdeadline +=
-		nsec_to_cycles(apic->vcpu, apic->lapic_timer.period);
+	ktime_t now = ktime_get();
+	u64 tscl = rdtsc();
+	ktime_t delta;
+
+	/*
+	 * Synchronize both deadlines to the same time source or
+	 * differences in the periods (caused by differences in the
+	 * underlying clocks or numerical approximation errors) will
+	 * cause the two to drift apart over time as the errors
+	 * accumulate.
+	 */
 	apic->lapic_timer.target_expiration =
 		ktime_add_ns(apic->lapic_timer.target_expiration,
 				apic->lapic_timer.period);
+	delta = ktime_sub(apic->lapic_timer.target_expiration, now);
+	apic->lapic_timer.tscdeadline = kvm_read_l1_tsc(apic->vcpu, tscl) +
+		nsec_to_cycles(apic->vcpu, delta);
 }
 
 static void start_sw_period(struct kvm_lapic *apic)