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Diffstat (limited to 'arch/x86/kvm/lapic.c')
-rw-r--r--arch/x86/kvm/lapic.c16
1 files changed, 14 insertions, 2 deletions
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index b74c9c1405b9..3773c4625114 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)