[PATCH][RFC] Use return value from kvm_set_irq() to re-inject PIT interrupts.

[Gleb Natapov <gleb@redhat.com>]

Use return value from kvm_set_irq() to track coalesced PIT interrupts
instead of ack/mask notifiers.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
index b857ca3..0b63991 100644
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -231,20 +231,7 @@ int pit_has_pending_timer(struct kvm_vcpu *vcpu)
 {
 	struct kvm_pit *pit = vcpu->kvm->arch.vpit;
 
-	if (pit && kvm_vcpu_is_bsp(vcpu) && pit->pit_state.irq_ack)
-		return atomic_read(&pit->pit_state.pit_timer.pending);
-	return 0;
-}
-
-static void kvm_pit_ack_irq(struct kvm_irq_ack_notifier *kian)
-{
-	struct kvm_kpit_state *ps = container_of(kian, struct kvm_kpit_state,
-						 irq_ack_notifier);
-	spin_lock(&ps->inject_lock);
-	if (atomic_dec_return(&ps->pit_timer.pending) < 0)
-		atomic_inc(&ps->pit_timer.pending);
-	ps->irq_ack = 1;
-	spin_unlock(&ps->inject_lock);
+	return atomic_read(&pit->pit_state.pit_timer.pending);
 }
 
 void __kvm_migrate_pit_timer(struct kvm_vcpu *vcpu)
@@ -297,7 +284,6 @@ static void create_pit_timer(struct kvm_kpit_state *ps, u32 val, int is_period)
 	pt->vcpu = pt->kvm->bsp_vcpu;
 
 	atomic_set(&pt->pending, 0);
-	ps->irq_ack = 1;
 
 	hrtimer_start(&pt->timer, ktime_add_ns(ktime_get(), interval),
 		      HRTIMER_MODE_ABS);
@@ -577,17 +563,6 @@ void kvm_pit_reset(struct kvm_pit *pit)
 	mutex_unlock(&pit->pit_state.lock);
 
 	atomic_set(&pit->pit_state.pit_timer.pending, 0);
-	pit->pit_state.irq_ack = 1;
-}
-
-static void pit_mask_notifer(struct kvm_irq_mask_notifier *kimn, bool mask)
-{
-	struct kvm_pit *pit = container_of(kimn, struct kvm_pit, mask_notifier);
-
-	if (!mask) {
-		atomic_set(&pit->pit_state.pit_timer.pending, 0);
-		pit->pit_state.irq_ack = 1;
-	}
 }
 
 static const struct kvm_io_device_ops pit_dev_ops = {
@@ -619,7 +594,6 @@ struct kvm_pit *kvm_create_pit(struct kvm *kvm, u32 flags)
 
 	mutex_init(&pit->pit_state.lock);
 	mutex_lock(&pit->pit_state.lock);
-	spin_lock_init(&pit->pit_state.inject_lock);
 
 	kvm->arch.vpit = pit;
 	pit->kvm = kvm;
@@ -628,17 +602,11 @@ struct kvm_pit *kvm_create_pit(struct kvm *kvm, u32 flags)
 	pit_state->pit = pit;
 	hrtimer_init(&pit_state->pit_timer.timer,
 		     CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
-	pit_state->irq_ack_notifier.gsi = 0;
-	pit_state->irq_ack_notifier.irq_acked = kvm_pit_ack_irq;
-	kvm_register_irq_ack_notifier(kvm, &pit_state->irq_ack_notifier);
 	pit_state->pit_timer.reinject = true;
 	mutex_unlock(&pit->pit_state.lock);
 
 	kvm_pit_reset(pit);
 
-	pit->mask_notifier.func = pit_mask_notifer;
-	kvm_register_irq_mask_notifier(kvm, 0, &pit->mask_notifier);
-
 	kvm_iodevice_init(&pit->dev, &pit_dev_ops);
 	ret = __kvm_io_bus_register_dev(&kvm->pio_bus, &pit->dev);
 	if (ret < 0)
@@ -670,10 +638,6 @@ void kvm_free_pit(struct kvm *kvm)
 	struct hrtimer *timer;
 
 	if (kvm->arch.vpit) {
-		kvm_unregister_irq_mask_notifier(kvm, 0,
-					       &kvm->arch.vpit->mask_notifier);
-		kvm_unregister_irq_ack_notifier(kvm,
-				&kvm->arch.vpit->pit_state.irq_ack_notifier);
 		mutex_lock(&kvm->arch.vpit->pit_state.lock);
 		timer = &kvm->arch.vpit->pit_state.pit_timer.timer;
 		hrtimer_cancel(timer);
@@ -683,12 +647,12 @@ void kvm_free_pit(struct kvm *kvm)
 	}
 }
 
-static void __inject_pit_timer_intr(struct kvm *kvm)
+static int __inject_pit_timer_intr(struct kvm *kvm)
 {
 	struct kvm_vcpu *vcpu;
-	int i;
+	int i, r;
 
-	kvm_set_irq(kvm, kvm->arch.vpit->irq_source_id, 0, 1);
+	r = kvm_set_irq(kvm, kvm->arch.vpit->irq_source_id, 0, 1);
 	kvm_set_irq(kvm, kvm->arch.vpit->irq_source_id, 0, 0);
 
 	/*
@@ -703,6 +667,8 @@ static void __inject_pit_timer_intr(struct kvm *kvm)
 	if (kvm->arch.vapics_in_nmi_mode > 0)
 		kvm_for_each_vcpu(i, vcpu, kvm)
 			kvm_apic_nmi_wd_deliver(vcpu);
+
+	return r;
 }
 
 void kvm_inject_pit_timer_irqs(struct kvm_vcpu *vcpu)
@@ -711,20 +677,14 @@ void kvm_inject_pit_timer_irqs(struct kvm_vcpu *vcpu)
 	struct kvm *kvm = vcpu->kvm;
 	struct kvm_kpit_state *ps;
 
-	if (pit) {
-		int inject = 0;
-		ps = &pit->pit_state;
-
-		/* Try to inject pending interrupts when
-		 * last one has been acked.
-		 */
-		spin_lock(&ps->inject_lock);
-		if (atomic_read(&ps->pit_timer.pending) && ps->irq_ack) {
-			ps->irq_ack = 0;
-			inject = 1;
-		}
-		spin_unlock(&ps->inject_lock);
-		if (inject)
-			__inject_pit_timer_intr(kvm);
-	}
+	if (!pit)
+		return;
+
+	ps = &pit->pit_state;
+
+	if (!atomic_read(&ps->pit_timer.pending))
+		return;
+
+	if (__inject_pit_timer_intr(kvm))
+		atomic_dec(&ps->pit_timer.pending);
 }
diff --git a/arch/x86/kvm/i8254.h b/arch/x86/kvm/i8254.h
index d4c1c7f..19937da 100644
--- a/arch/x86/kvm/i8254.h
+++ b/arch/x86/kvm/i8254.h
@@ -28,8 +28,6 @@ struct kvm_kpit_state {
 	struct mutex lock;
 	struct kvm_pit *pit;
 	spinlock_t inject_lock;
-	unsigned long irq_ack;
-	struct kvm_irq_ack_notifier irq_ack_notifier;
 };
 
 struct kvm_pit {
@@ -39,7 +37,6 @@ struct kvm_pit {
 	struct kvm *kvm;
 	struct kvm_kpit_state pit_state;
 	int irq_source_id;
-	struct kvm_irq_mask_notifier mask_notifier;
 };
 
 #define KVM_PIT_BASE_ADDRESS	    0x40
--
			Gleb.