[PATCH v4 09/36] x86/bugs: Only allow retbleed=stuff on Intel

[David Kaplan]

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@xxxxxxx>
---
 arch/x86/kernel/cpu/bugs.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index de120ecb752d..4af342d226c8 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1178,6 +1178,10 @@ 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 {
-- 
2.34.1