KVM: use proper hrtimer function to retrieve expiration time

hrtimer->base can be temporarily NULL due to racing hrtimer_start.
See switch_hrtimer_base/lock_hrtimer_base.

Use hrtimer_get_remaining which is robust against it.

CC: stable@kernel.org
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/kvm/i8254.c

@@ -116,7 +116,7 @@ static s64 __kpit_elapsed(struct kvm *kvm)
 	 * itself with the initial count and continues counting
 	 * from there.
 	 */
-	remaining = hrtimer_expires_remaining(&ps->pit_timer.timer);
+	remaining = hrtimer_get_remaining(&ps->pit_timer.timer);
 	elapsed = ps->pit_timer.period - ktime_to_ns(remaining);
 	elapsed = mod_64(elapsed, ps->pit_timer.period);
 

arch/x86/kvm/lapic.c

@@ -521,7 +521,7 @@ static u32 apic_get_tmcct(struct kvm_lapic *apic)
 	if (apic_get_reg(apic, APIC_TMICT) == 0)
 		return 0;
 
-	remaining = hrtimer_expires_remaining(&apic->lapic_timer.timer);
+	remaining = hrtimer_get_remaining(&apic->lapic_timer.timer);
 	if (ktime_to_ns(remaining) < 0)
 		remaining = ktime_set(0, 0);