From 8c35f237fb5664d30aa90448c3d6cea0cbb43f35 Mon Sep 17 00:00:00 2001
From: Avi Kivity <avi@qumranet.com>
Date: Mon, 25 Feb 2008 10:28:31 +0200
Subject: [PATCH] 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 <avi@qumranet.com>
---
virt/kvm/ioapic.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/virt/kvm/ioapic.c b/virt/kvm/ioapic.c
index 317f8e211cd2a..4232fd75dd20b 100644
--- 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;
--
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