KVM: Route irq 0 to vcpu 0 exclusively

Some Linux versions allow the timer interrupt to be processed by more than one cpu, leading to hangs due to tsc instability. Work around the issue by only disaptching the interrupt to vcpu 0. Problem analyzed (and patch tested) by Sheng Yang. Signed-off-by: Avi Kivity <[email protected]>
josf · Mar 4, 2008 · 8c35f23 · 8c35f23
1 parent 0b975a3
commit 8c35f23
Showing 1 changed file with 8 additions and 0 deletions.
diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
@@ -211,6 +211,10 @@ static void ioapic_deliver(struct kvm_ioapic *ioapic, int irq)
 	case IOAPIC_LOWEST_PRIORITY:
 		vcpu = kvm_get_lowest_prio_vcpu(ioapic->kvm, vector,
 				deliver_bitmask);
+#ifdef CONFIG_X86
+		if (irq == 0)
+			vcpu = ioapic->kvm->vcpus[0];
+#endif
 		if (vcpu != NULL)
 			ioapic_inj_irq(ioapic, vcpu, vector,
 				       trig_mode, delivery_mode);
@@ -220,6 +224,10 @@ static void ioapic_deliver(struct kvm_ioapic *ioapic, int irq)
 				     deliver_bitmask, vector, IOAPIC_LOWEST_PRIORITY);
 		break;
 	case IOAPIC_FIXED:
+#ifdef CONFIG_X86
+		if (irq == 0)
+			deliver_bitmask = 1;
+#endif
 		for (vcpu_id = 0; deliver_bitmask != 0; vcpu_id++) {
 			if (!(deliver_bitmask & (1 << vcpu_id)))
 				continue;