[PATCH v3 7/7] x86/bugs: Report correct retbleed mitigation status

[David Kaplan <david.kaplan@amd.com>]

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>
---
 arch/x86/kernel/cpu/bugs.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 1f3a20f6fac0..45c9605fc5c3 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/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;
+			}
 		}
 	}
 
-- 
2.34.1