diff --git a/sys/amd64/vmm/vmm_dev_machdep.c b/sys/amd64/vmm/vmm_dev_machdep.c
--- a/sys/amd64/vmm/vmm_dev_machdep.c
+++ b/sys/amd64/vmm/vmm_dev_machdep.c
@@ -530,6 +530,13 @@
 				free(entries, M_VMMDEV);
 				break;
 			}
+		} else {
+			/*
+			 * Not using "legacy" handling and no cpuid entries
+			 * given isn't allowed either.
+			 */
+			error = EINVAL;
+			break;
 		}
 
 		vcpu_cpuid_config_t vm_cfg = {