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@intel.com>
Link: https://lore.kernel.org/r/20240906043413.1049633-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 1a6dc85cde180ceeff87de9ecace03926a772d2f..e57cd849354b08dee921f6e5a7de7ffbaa6725ea 100644 (file)
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4305,7 +4305,8 @@ 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);