linux-kernel - [PATCH 1/2] x86/spectre_v2: Fix mitigation default on Intel

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Message-ID: <20250520-eibrs-fix-v1-1-91bacd35ed09@linux.intel.com>
Date: Tue, 20 May 2025 22:35:20 -0700
From: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
To: x86@...nel.org
Cc: David Kaplan <david.kaplan@....com>, linux-kernel@...r.kernel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Josh Poimboeuf <jpoimboe@...nel.org>
Subject: [PATCH 1/2] x86/spectre_v2: Fix mitigation default on Intel

commit 480e803dacf8 ("x86/bugs: Restructure spectre_v2 mitigation")
inadvertently changed the spectre-v2 mitigation default from eIBRS to IBRS
on Intel. While splitting the spectre_v2 mitigation in select/update/apply
functions, eIBRS and IBRS selection logic was separated in select and
update.

This caused IBRS selection to not consider that eIBRS mitigation is already
selected, fix it.

Fixes: commit 480e803dacf8 ("x86/bugs: Restructure spectre_v2 mitigation")
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
---
 arch/x86/kernel/cpu/bugs.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 3d5796d25f786837df59f9ce6358bc875cabe731..7f94e6a5497d9a2d312a76095e48d6b364565777 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2105,7 +2105,8 @@ static void __init spectre_v2_select_mitigation(void)
 
 static void __init spectre_v2_update_mitigation(void)
 {
-	if (spectre_v2_cmd == SPECTRE_V2_CMD_AUTO) {
+	if (spectre_v2_cmd == SPECTRE_V2_CMD_AUTO &&
+	    !spectre_v2_in_eibrs_mode(spectre_v2_enabled)) {
 		if (IS_ENABLED(CONFIG_MITIGATION_IBRS_ENTRY) &&
 		    boot_cpu_has_bug(X86_BUG_RETBLEED) &&
 		    retbleed_mitigation != RETBLEED_MITIGATION_NONE &&

-- 
2.34.1