linux-kernel - [PATCH v2 3/7] KVM: nVMX: Suppress external interrupt VM-Exit injection if there's no IRQ

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Message-ID: <20240906043413.1049633-4-seanjc@google.com>
Date: Thu,  5 Sep 2024 21:34:09 -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, 
	Nathan Chancellor <nathan@...nel.org>, Chao Gao <chao.gao@...el.com>, 
	Zeng Guang <guang.zeng@...el.com>
Subject: [PATCH v2 3/7] 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.

Reviewed-by: Chao Gao <chao.gao@...el.com>
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 e6af5f1d3b61..6b7e0ab0e45e 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4304,7 +4304,8 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu)
 		}
 
 		irq = kvm_apic_has_interrupt(vcpu);
-		WARN_ON_ONCE(irq < 0);
+		if (WARN_ON_ONCE(irq < 0))
+			goto no_vmexit;
 
 		nested_vmx_vmexit(vcpu, EXIT_REASON_EXTERNAL_INTERRUPT,
 				  INTR_INFO_VALID_MASK | INTR_TYPE_EXT_INTR | irq, 0);
-- 
2.46.0.469.g59c65b2a67-goog