KVM: x86: Fix and refactor NMI watchdog emulation

This patch refactors the NMI watchdog delivery patch, consolidating
tests and providing a proper API for delivering watchdog events.

An included micro-optimization is to check only for apic_hw_enabled in
kvm_apic_local_deliver (the test for LVT mask is covering the
soft-disabled case already).
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Acked-by: Sheng Yang <sheng@linux.intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/kvm/i8254.c

@@ -612,15 +612,18 @@ static void __inject_pit_timer_intr(struct kvm *kvm)
 	mutex_unlock(&kvm->lock);
 
 	/*
-	 * Provides NMI watchdog support in IOAPIC mode.
-	 * The route is: PIT -> PIC -> LVT0 in NMI mode,
-	 * timer IRQs will continue to flow through the IOAPIC.
+	 * Provides NMI watchdog support via Virtual Wire mode.
+	 * The route is: PIT -> PIC -> LVT0 in NMI mode.
+	 *
+	 * Note: Our Virtual Wire implementation is simplified, only
+	 * propagating PIT interrupts to all VCPUs when they have set
+	 * LVT0 to NMI delivery. Other PIC interrupts are just sent to
+	 * VCPU0, and only if its LVT0 is in EXTINT mode.
 	 */
 	for (i = 0; i < KVM_MAX_VCPUS; ++i) {
 		vcpu = kvm->vcpus[i];
-		if (!vcpu)
-			continue;
-		kvm_apic_local_deliver(vcpu, APIC_LVT0);
+		if (vcpu)
+			kvm_apic_nmi_wd_deliver(vcpu);
 	}
 }
 

arch/x86/kvm/irq.h

@@ -87,7 +87,7 @@ void kvm_pic_reset(struct kvm_kpic_state *s);
 void kvm_timer_intr_post(struct kvm_vcpu *vcpu, int vec);
 void kvm_inject_pending_timer_irqs(struct kvm_vcpu *vcpu);
 void kvm_inject_apic_timer_irqs(struct kvm_vcpu *vcpu);
-int kvm_apic_local_deliver(struct kvm_vcpu *vcpu, int lvt_type);
+void kvm_apic_nmi_wd_deliver(struct kvm_vcpu *vcpu);
 void __kvm_migrate_apic_timer(struct kvm_vcpu *vcpu);
 void __kvm_migrate_pit_timer(struct kvm_vcpu *vcpu);
 void __kvm_migrate_timers(struct kvm_vcpu *vcpu);

arch/x86/kvm/lapic.c

@@ -973,14 +973,12 @@ int apic_has_pending_timer(struct kvm_vcpu *vcpu)
 	return 0;
 }
 
-int kvm_apic_local_deliver(struct kvm_vcpu *vcpu, int lvt_type)
+static int kvm_apic_local_deliver(struct kvm_lapic *apic, int lvt_type)
 {
-	struct kvm_lapic *apic = vcpu->arch.apic;
+	u32 reg = apic_get_reg(apic, lvt_type);
 	int vector, mode, trig_mode;
-	u32 reg;
 
-	if (apic && apic_enabled(apic)) {
-		reg = apic_get_reg(apic, lvt_type);
+	if (apic_hw_enabled(apic) && !(reg & APIC_LVT_MASKED)) {
 		vector = reg & APIC_VECTOR_MASK;
 		mode = reg & APIC_MODE_MASK;
 		trig_mode = reg & APIC_LVT_LEVEL_TRIGGER;
@@ -989,9 +987,12 @@ int kvm_apic_local_deliver(struct kvm_vcpu *vcpu, int lvt_type)
 	return 0;
 }
 
-static inline int __inject_apic_timer_irq(struct kvm_lapic *apic)
+void kvm_apic_nmi_wd_deliver(struct kvm_vcpu *vcpu)
 {
-	return kvm_apic_local_deliver(apic->vcpu, APIC_LVTT);
+	struct kvm_lapic *apic = vcpu->arch.apic;
+
+	if (apic)
+		kvm_apic_local_deliver(apic, APIC_LVT0);
 }
 
 static enum hrtimer_restart apic_timer_fn(struct hrtimer *data)
@@ -1086,9 +1087,8 @@ void kvm_inject_apic_timer_irqs(struct kvm_vcpu *vcpu)
 {
 	struct kvm_lapic *apic = vcpu->arch.apic;
 
-	if (apic && apic_lvt_enabled(apic, APIC_LVTT) &&
-		atomic_read(&apic->timer.pending) > 0) {
-		if (__inject_apic_timer_irq(apic))
+	if (apic && atomic_read(&apic->timer.pending) > 0) {
+		if (kvm_apic_local_deliver(apic, APIC_LVTT))
 			atomic_dec(&apic->timer.pending);
 	}
 }