x86/bugs: Allow retbleed=stuff only on Intel

The retbleed=stuff mitigation is only applicable for Intel CPUs affected
by retbleed.  If this option is selected for another vendor, print a
warning and fall back to the AUTO option.

Signed-off-by: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/20250418161721.1855190-10-david.kaplan@amd.com

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 1a42abb289ac641a44457b140e59eb2ef3561adf..7edf42912cdf83a8846d7fdc37314f74356f6c91 100644 (file)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1191,6 +1191,10 @@ static void __init retbleed_select_mitigation(void)
        case RETBLEED_CMD_STUFF:
                if (IS_ENABLED(CONFIG_MITIGATION_CALL_DEPTH_TRACKING) &&
                    spectre_v2_enabled == SPECTRE_V2_RETPOLINE) {
+                       if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL) {
+                               pr_err("WARNING: retbleed=stuff only supported for Intel CPUs.\n");
+                               goto do_cmd_auto;
+                       }
                        retbleed_mitigation = RETBLEED_MITIGATION_STUFF;
 
                } else {