[PATCH AUTOSEL 5.18 22/54] x86/bugs: Do IBPB fallback check only once

[Sasha Levin]

From: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>

[ Upstream commit 0fe4aeea9c01baabecc8c3afc7889c809d939bc2 ]

When booting with retbleed=auto, if the kernel wasn't built with
CONFIG_CC_HAS_RETURN_THUNK, the mitigation falls back to IBPB.  Make
sure a warning is printed in that case.  The IBPB fallback check is done
twice, but it really only needs to be done once.

Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 arch/x86/kernel/cpu/bugs.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index ca5f90375a7d..99c45cf27ae6 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -871,8 +871,9 @@ static void __init retbleed_select_mitigation(void)
 			retbleed_mitigation = RETBLEED_MITIGATION_UNRET;
 
 		/*
-		 * The Intel mitigation (IBRS) was already selected in
-		 * spectre_v2_select_mitigation().
+		 * The Intel mitigation (IBRS or eIBRS) was already selected in
+		 * spectre_v2_select_mitigation().  'retbleed_mitigation' will
+		 * be set accordingly below.
 		 */
 
 		break;
-- 
2.35.1