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>

3 files changed, 20 insertions, 17 deletions

diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
index 580cc1d01c7d..b6fcf5a9e502 100644
--- a/arch/x86/kvm/i8254.c
+++ b/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);
         }
 }
 
diff --git a/arch/x86/kvm/irq.h b/arch/x86/kvm/irq.h
index 71e37a530cf7..b9e9051650ea 100644
--- a/arch/x86/kvm/irq.h
+++ b/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);
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 304f9ddbdd51..0b0d413f0af5 100644
--- a/arch/x86/kvm/lapic.c
+++ b/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);
         }
 }