The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     83d4b19331f3a5d5829d338a0a64b69c9c28b36e
Gitweb:        https://git.kernel.org/tip/83d4b19331f3a5d5829d338a0a64b69c9c28b36e
Author:        David Kaplan <david.kaplan@amd.com>
AuthorDate:    Fri, 18 Apr 2025 11:17:14 -05:00
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Mon, 28 Apr 2025 19:55:50 +02:00

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
---
 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 1a42abb..7edf429 100644
--- 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 {