KVM: x86: thoroughly disarm LAPIC timer around TSC deadline switch

Our routines look at tscdeadline and period when deciding state of a
timer.  The timer is disarmed when switching between TSC deadline and
other modes, so we should set everything to disarmed state.
Signed-off-by: NRadim Krčmář <rkrcmar@redhat.com>
Reviewed-by: NWanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/lapic.c

@@ -1330,8 +1330,10 @@ static void apic_update_lvtt(struct kvm_lapic *apic)
 	if (apic->lapic_timer.timer_mode != timer_mode) {
 		if (apic_lvtt_tscdeadline(apic) != (timer_mode ==
 				APIC_LVT_TIMER_TSCDEADLINE)) {
-			kvm_lapic_set_reg(apic, APIC_TMICT, 0);
 			hrtimer_cancel(&apic->lapic_timer.timer);
+			kvm_lapic_set_reg(apic, APIC_TMICT, 0);
+			apic->lapic_timer.period = 0;
+			apic->lapic_timer.tscdeadline = 0;
 		}
 		apic->lapic_timer.timer_mode = timer_mode;
 		limit_periodic_timer_frequency(apic);