linux-kernel - [PATCH 2/6] KVM: nVMX: Suppress external interrupt VM-Exit injection if there's no IRQ

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Message-ID: <20240720000138.3027780-3-seanjc@google.com>
Date: Fri, 19 Jul 2024 17:01:34 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Chao Gao <chao.gao@...el.com>, Zeng Guang <guang.zeng@...el.com>
Subject: [PATCH 2/6] KVM: nVMX: Suppress external interrupt VM-Exit injection
 if there's no IRQ

In the should-be-impossible scenario that kvm_cpu_get_interrupt() doesn't
return a valid vector after checking kvm_cpu_has_interrupt(), skip VM-Exit
injection to reduce the probability of crashing/confusing L1.  Now that
KVM gets the IRQ _before_ calling nested_vmx_vmexit(), squashing the
VM-Exit injection is trivial since there are no actions that need to be
undone.

Cc: stable@...r.kernel.org
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/kvm/vmx/nested.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index b3e17635f7e3..b042b70560f2 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4295,7 +4295,8 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu)
 			int irq;
 
 			irq = kvm_cpu_get_interrupt(vcpu);
-			WARN_ON_ONCE(irq < 0);
+			if (WARN_ON_ONCE(irq < 0))
+				goto no_vmexit;
 
 			exit_intr_info = INTR_INFO_VALID_MASK | INTR_TYPE_EXT_INTR | irq;
 		} else {
-- 
2.45.2.1089.g2a221341d9-goog