diff --git a/arch/x86/kvm/irq.h b/arch/x86/kvm/irq.h
index 1a84ea31e7fd..eeaf527cecc4 100644
--- a/arch/x86/kvm/irq.h
+++ b/arch/x86/kvm/irq.h
@@ -118,6 +118,22 @@ int kvm_cpu_has_extint(struct kvm_vcpu *v);
 int kvm_cpu_get_extint(struct kvm_vcpu *v);
 int kvm_cpu_get_interrupt(struct kvm_vcpu *v);
 
+static inline void kvm_warn_on_lost_irq(struct kvm_vcpu *vcpu)
+{
+	/*
+	 * WARN if an IRQ was lost between detecting the IRQ and grabbing the
+	 * IRQ for injection, unless it's possible the lost IRQ was due to one
+	 * of the exceptional cases below.
+	 *
+	 * If the VM has an in-kernel PIC, the ExtINT handling that's routed
+	 * through KVM's virtual PIC is tracked per-VM, not per-vCPU.  If
+	 * another vCPU grabs the IRQ, or deasserts the interrupt (which is
+	 * level-triggered), then it's both expected and "fine" for an IRQ
+	 * seemingly be "lost" from this vCPU's perspective.
+	 */
+	WARN_ON_ONCE(!pic_in_kernel(vcpu->kvm));
+}
+
 void kvm_inject_pending_timer_irqs(struct kvm_vcpu *vcpu);
 void kvm_inject_apic_timer_irqs(struct kvm_vcpu *vcpu);
 void kvm_apic_nmi_wd_deliver(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index a9af4e9e6657..ed9dd03a1ddf 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4467,8 +4467,10 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu)
 		}
 
 		irq = kvm_apic_has_interrupt(vcpu);
-		if (WARN_ON_ONCE(irq < 0))
+		if (unlikely(irq < 0)) {
+			kvm_warn_on_lost_irq(vcpu);
 			goto no_vmexit;
+		}
 
 		/*
 		 * If the IRQ is L2's PI notification vector, process posted
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index dfaf80efec4b..3be5024045da 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7733,10 +7733,12 @@ static int kvm_check_and_inject_events(struct kvm_vcpu *vcpu,
 		if (r) {
 			int irq = kvm_cpu_get_interrupt(vcpu);
 
-			if (!WARN_ON_ONCE(irq == -1)) {
+			if (likely(irq != -1)) {
 				kvm_queue_interrupt(vcpu, irq, false);
 				kvm_x86_call(inject_irq)(vcpu, false);
 				WARN_ON(kvm_x86_call(interrupt_allowed)(vcpu, true) < 0);
+			} else {
+				kvm_warn_on_lost_irq(vcpu);
 			}
 		}
 		if (kvm_cpu_has_injectable_intr(vcpu))