diff --git a/kernel/cpu.c b/kernel/cpu.c
index 127a69b8b192..f370a0f43005 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -2308,6 +2308,9 @@ static int __init mitigations_parse_cmdline(char *arg)
 		cpu_mitigations = CPU_MITIGATIONS_AUTO;
 	else if (!strcmp(arg, "auto,nosmt"))
 		cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT;
+	else
+		pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
+			arg);
 
 	return 0;
 }