KVM: SVM: WARN if an invalid posted interrupt IRTE entry is added

Now that the AMD IOMMU doesn't signal success incorrectly, WARN if KVM
attempts to track an AMD IRTE entry without metadata.

Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-ID: <20250404193923.1413163-8-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Author: sean-jc

arch/x86/kvm/svm/avic.c

@@ -796,12 +796,15 @@ static int svm_ir_list_add(struct vcpu_svm *svm, struct amd_iommu_pi_data *pi)
 	struct amd_svm_iommu_ir *ir;
 	u64 entry;
 
+	if (WARN_ON_ONCE(!pi->ir_data))
+		return -EINVAL;
+
 	/**
 	 * In some cases, the existing irte is updated and re-set,
 	 * so we need to check here if it's already been * added
 	 * to the ir_list.
 	 */
-	if (pi->ir_data && (pi->prev_ga_tag != 0)) {
+	if (pi->prev_ga_tag) {
 		struct kvm *kvm = svm->vcpu.kvm;
 		u32 vcpu_id = AVIC_GATAG_TO_VCPUID(pi->prev_ga_tag);
 		struct kvm_vcpu *prev_vcpu = kvm_get_vcpu_by_id(kvm, vcpu_id);