There is a window open between testing of pending IRQ's
and assignment of guest_mode in __vcpu_run.
Injection of IRQ's can race with __vcpu_run as follows:
CPU0 CPU1
kvm_x86_ops->run()
vcpu->guest_mode = 0 SET_IRQ_LINE ioctl
..
kvm_x86_ops->inject_pending_irq
kvm_cpu_has_interrupt()
apic_test_and_set_irr()
kvm_vcpu_kick
if (vcpu->guest_mode)
send_ipi()
vcpu->guest_mode = 1
So move guest_mode=1 assignment before ->inject_pending_irq, and make
sure that it won't reorder after it.
Signed-off-by: Marcelo Tosatti <[EMAIL PROTECTED]>
Index: kvm/arch/x86/kvm/x86.c
===================================================================
--- kvm.orig/arch/x86/kvm/x86.c
+++ kvm/arch/x86/kvm/x86.c
@@ -2777,6 +2777,13 @@ again:
goto out;
}
+ vcpu->guest_mode = 1;
+ /*
+ * Make sure that guest_mode assignment won't happen after
+ * testing the pending IRQ vector bitmap.
+ */
+ smp_wmb();
+
if (vcpu->arch.exception.pending)
__queue_exception(vcpu);
else if (irqchip_in_kernel(vcpu->kvm))
@@ -2788,7 +2795,6 @@ again:
up_read(&vcpu->kvm->slots_lock);
- vcpu->guest_mode = 1;
kvm_guest_enter();
if (vcpu->requests)
@@ -3944,11 +3950,12 @@ static void vcpu_kick_intr(void *info)
void kvm_vcpu_kick(struct kvm_vcpu *vcpu)
{
int ipi_pcpu = vcpu->cpu;
+ int cpu = smp_processor_id();
if (waitqueue_active(&vcpu->wq)) {
wake_up_interruptible(&vcpu->wq);
++vcpu->stat.halt_wakeup;
}
- if (vcpu->guest_mode)
+ if (vcpu->guest_mode && vcpu->cpu != cpu)
smp_call_function_single(ipi_pcpu, vcpu_kick_intr, vcpu, 0, 0);
}
--
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