From: Josh Poimboeuf <jpoimboe@kernel.org>
Date: Tue, 14 Jun 2022 15:07:19 -0700
Subject: x86/bugs: Do IBPB fallback check only once
Git-commit: 0fe4aeea9c01baabecc8c3afc7889c809d939bc2
Patch-mainline: v5.19-rc4
References: bsc#1199657 CVE-2022-29900 CVE-2022-29901
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@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
---
arch/x86/kernel/cpu/bugs.c | 15 +++++----------
1 file changed, 5 insertions(+), 10 deletions(-)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 04077d13b3ae..108bd74289c5 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -891,18 +891,13 @@ static void __init retbleed_select_mitigation(void)
case RETBLEED_CMD_AUTO:
default:
if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
- boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
-
- if (IS_ENABLED(CONFIG_RETPOLINE) &&
- IS_ENABLED(CONFIG_CC_HAS_RETURN_THUNK))
- retbleed_mitigation = RETBLEED_MITIGATION_UNRET;
- else
- retbleed_mitigation = RETBLEED_MITIGATION_IBPB;
- }
+ boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)
+ 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;