x86: KVM: SVM: add support for Invalid IPI Vector interception

In later revisions of AMD's APM, there is a new 'incomplete IPI' exit code:

"Invalid IPI Vector - The vector for the specified IPI was set to an
illegal value (VEC < 16)"

Note that tests on Zen2 machine show that this VM exit doesn't happen and
instead AVIC just does nothing.

Add support for this exit code by doing nothing, instead of filling
the kernel log with errors.

Also replace an unthrottled 'pr_err()' if another unknown incomplete
IPI exit happens with vcpu_unimpl()

(e.g in case AMD adds yet another 'Invalid IPI' exit reason)

Cc: <stable@vger.kernel.org>
Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20230928173354.217464-3-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Author: Maxim Levitsky

arch/x86/include/asm/svm.h

@@ -268,6 +268,7 @@ enum avic_ipi_failure_cause {
 	AVIC_IPI_FAILURE_TARGET_NOT_RUNNING,
 	AVIC_IPI_FAILURE_INVALID_TARGET,
 	AVIC_IPI_FAILURE_INVALID_BACKING_PAGE,
+	AVIC_IPI_FAILURE_INVALID_IPI_VECTOR,
 };
 
 #define AVIC_PHYSICAL_MAX_INDEX_MASK	GENMASK_ULL(8, 0)

arch/x86/kvm/svm/avic.c

@@ -529,8 +529,11 @@ int avic_incomplete_ipi_interception(struct kvm_vcpu *vcpu)
 	case AVIC_IPI_FAILURE_INVALID_BACKING_PAGE:
 		WARN_ONCE(1, "Invalid backing page\n");
 		break;
+	case AVIC_IPI_FAILURE_INVALID_IPI_VECTOR:
+		/* Invalid IPI with vector < 16 */
+		break;
 	default:
-		pr_err("Unknown IPI interception\n");
+		vcpu_unimpl(vcpu, "Unknown avic incomplete IPI interception\n");
 	}
 
 	return 1;