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KVM: x86: check the kvm_cpu_get_interrupt result before using it

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The code was blindly assuming that kvm_cpu_get_interrupt never returns -1
when there is a pending interrupt.

While this should be true, a bug in KVM can still cause this.

If -1 is returned, the code before this patch was converting it to 0xFF,
and 0xFF interrupt was injected to the guest, which results in an issue
which was hard to debug.

Add WARN_ON_ONCE to catch this case and	skip the injection
if this happens again.

Signed-off-by: Maxim Levitsky <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
This commit is contained in:
Maxim Levitsky authored and Paolo Bonzini committed 2023-07-29 11:05:25 -04:00
1 parent cff540ebef
commit bf672720e8
1 file changed
+7 -3
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arch/x86/kvm/x86.c
+7 -3
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@@ -10203,9 +10203,13 @@ static int kvm_check_and_inject_events(struct kvm_vcpu *vcpu,
if (r < 0)
goto out;
if (r) {
kvm_queue_interrupt(vcpu, kvm_cpu_get_interrupt(vcpu), false);
static_call(kvm_x86_inject_irq)(vcpu, false);
WARN_ON(static_call(kvm_x86_interrupt_allowed)(vcpu, true) < 0);
int irq = kvm_cpu_get_interrupt(vcpu);
if (!WARN_ON_ONCE(irq == -1)) {
kvm_queue_interrupt(vcpu, irq, false);
static_call(kvm_x86_inject_irq)(vcpu, false);
WARN_ON(static_call(kvm_x86_interrupt_allowed)(vcpu, true) < 0);
}
}
if (kvm_cpu_has_injectable_intr(vcpu))
static_call(kvm_x86_enable_irq_window)(vcpu);