KVM: arm/arm64: Rework kvm_timer_should_fire

kvm_timer_should_fire() can be called in two different situations from
the kvm_vcpu_block().

The first case is before calling kvm_timer_schedule(), used for wait
polling, and in this case the VCPU thread is running and the timer state
is loaded onto the hardware so all we have to do is check if the virtual
interrupt lines are asserted, becasue the timer interrupt handler
functions will raise those lines as appropriate.

The second case is inside the wait loop of kvm_vcpu_block(), where we
have already called kvm_timer_schedule() and therefore the hardware will
be disabled and the software view of the timer state is up to date
(timer->loaded is false), and so we can simply check if the timer should
fire by looking at the software state.

Signed-off-by: Christoffer Dall <cdall@linaro.org>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>

include/kvm/arm_arch_timer.h

@@ -78,7 +78,8 @@ int kvm_arm_timer_set_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr);
 int kvm_arm_timer_get_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr);
 int kvm_arm_timer_has_attr(struct kvm_vcpu *vcpu, struct kvm_device_attr *attr);
 
-bool kvm_timer_should_fire(struct arch_timer_context *timer_ctx);
+bool kvm_timer_is_pending(struct kvm_vcpu *vcpu);
+
 void kvm_timer_schedule(struct kvm_vcpu *vcpu);
 void kvm_timer_unschedule(struct kvm_vcpu *vcpu);
 

virt/kvm/arm/arch_timer.c

@@ -49,6 +49,7 @@ static const struct kvm_irq_level default_vtimer_irq = {
 static bool kvm_timer_irq_can_fire(struct arch_timer_context *timer_ctx);
 static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level,
 				 struct arch_timer_context *timer_ctx);
+static bool kvm_timer_should_fire(struct arch_timer_context *timer_ctx);
 
 u64 kvm_phys_timer_read(void)
 {
@@ -226,7 +227,7 @@ static enum hrtimer_restart kvm_phys_timer_expire(struct hrtimer *hrt)
 	return HRTIMER_NORESTART;
 }
 
-bool kvm_timer_should_fire(struct arch_timer_context *timer_ctx)
+static bool kvm_timer_should_fire(struct arch_timer_context *timer_ctx)
 {
 	u64 cval, now;
 
@@ -239,6 +240,25 @@ bool kvm_timer_should_fire(struct arch_timer_context *timer_ctx)
 	return cval <= now;
 }
 
+bool kvm_timer_is_pending(struct kvm_vcpu *vcpu)
+{
+	struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
+	struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
+
+	if (vtimer->irq.level || ptimer->irq.level)
+		return true;
+
+	/*
+	 * When this is called from withing the wait loop of kvm_vcpu_block(),
+	 * the software view of the timer state is up to date (timer->loaded
+	 * is false), and so we can simply check if the timer should fire now.
+	 */
+	if (!vtimer->loaded && kvm_timer_should_fire(vtimer))
+		return true;
+
+	return kvm_timer_should_fire(ptimer);
+}
+
 /*
  * Reflect the timer output level into the kvm_run structure
  */

virt/kvm/arm/arm.c

@@ -307,8 +307,7 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
 
 int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
 {
-	return kvm_timer_should_fire(vcpu_vtimer(vcpu)) ||
-	       kvm_timer_should_fire(vcpu_ptimer(vcpu));
+	return kvm_timer_is_pending(vcpu);
 }
 
 void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu)