x86/bugs: Report correct retbleed mitigation status

JIRA: https://issues.redhat.com/browse/RHEL-119227

commit 930f236
Author: David Kaplan <david.kaplan@amd.com>
Date:   Mon, 15 Sep 2025 08:47:06 -0500

    x86/bugs: Report correct retbleed mitigation status

    On Intel CPUs, the default retbleed mitigation is IBRS/eIBRS but this
    requires that a similar spectre_v2 mitigation is applied.  If the user
    selects a different spectre_v2 mitigation (like spectre_v2=retpoline) a
    warning is printed but sysfs will still report 'Mitigation: IBRS' or
    'Mitigation: Enhanced IBRS'.  This is incorrect because retbleed is not
    mitigated, and IBRS is not actually set.

    Fix this by choosing RETBLEED_MITIGATION_NONE in this scenario so the
    kernel correctly reports the system as vulnerable to retbleed.

    Signed-off-by: David Kaplan <david.kaplan@amd.com>
    Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
    Link: https://lore.kernel.org/20250915134706.3201818-1-david.kaplan@amd.com

Signed-off-by: Waiman Long <longman@redhat.com>

Author: Waiman-Long

arch/x86/kernel/cpu/bugs.c

@@ -1462,8 +1462,10 @@ static void __init retbleed_update_mitigation(void)
 			retbleed_mitigation = RETBLEED_MITIGATION_EIBRS;
 			break;
 		default:
-			if (retbleed_mitigation != RETBLEED_MITIGATION_STUFF)
+			if (retbleed_mitigation != RETBLEED_MITIGATION_STUFF) {
 				pr_err(RETBLEED_INTEL_MSG);
+				retbleed_mitigation = RETBLEED_MITIGATION_NONE;
+			}
 		}
 	}