linux-kernel - [PATCH AUTOSEL 6.10 063/197] x86/bugs: Fix handling when SRSO mitigation is disabled

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Message-ID: <20240925115823.1303019-63-sashal@kernel.org>
Date: Wed, 25 Sep 2024 07:51:22 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: David Kaplan <david.kaplan@....com>,
	Borislav Petkov <bp@...en8.de>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Sasha Levin <sashal@...nel.org>,
	tglx@...utronix.de,
	peterz@...radead.org,
	mingo@...hat.com,
	dave.hansen@...ux.intel.com,
	x86@...nel.org
Subject: [PATCH AUTOSEL 6.10 063/197] x86/bugs: Fix handling when SRSO mitigation is disabled

From: David Kaplan <david.kaplan@....com>

[ Upstream commit 1dbb6b1495d472806fef1f4c94f5b3e4c89a3c1d ]

When the SRSO mitigation is disabled, either via mitigations=off or
spec_rstack_overflow=off, the warning about the lack of IBPB-enhancing
microcode is printed anyway.

This is unnecessary since the user has turned off the mitigation.

  [ bp: Massage, drop SBPB rationale as it doesn't matter because when
    mitigations are disabled x86_pred_cmd is not being used anyway. ]

Signed-off-by: David Kaplan <david.kaplan@....com>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Acked-by: Josh Poimboeuf <jpoimboe@...nel.org>
Link: https://lore.kernel.org/r/20240904150711.193022-1-david.kaplan@amd.com
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/kernel/cpu/bugs.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index b6f927f6c567e..47c84503ad9be 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2545,10 +2545,9 @@ static void __init srso_select_mitigation(void)
 {
 	bool has_microcode = boot_cpu_has(X86_FEATURE_IBPB_BRTYPE);
 
-	if (cpu_mitigations_off())
-		return;
-
-	if (!boot_cpu_has_bug(X86_BUG_SRSO)) {
+	if (!boot_cpu_has_bug(X86_BUG_SRSO) ||
+	    cpu_mitigations_off() ||
+	    srso_cmd == SRSO_CMD_OFF) {
 		if (boot_cpu_has(X86_FEATURE_SBPB))
 			x86_pred_cmd = PRED_CMD_SBPB;
 		return;
@@ -2579,11 +2578,6 @@ static void __init srso_select_mitigation(void)
 	}
 
 	switch (srso_cmd) {
-	case SRSO_CMD_OFF:
-		if (boot_cpu_has(X86_FEATURE_SBPB))
-			x86_pred_cmd = PRED_CMD_SBPB;
-		return;
-
 	case SRSO_CMD_MICROCODE:
 		if (has_microcode) {
 			srso_mitigation = SRSO_MITIGATION_MICROCODE;
@@ -2637,6 +2631,8 @@ static void __init srso_select_mitigation(void)
 			pr_err("WARNING: kernel not compiled with MITIGATION_SRSO.\n");
                 }
 		break;
+	default:
+		break;
 	}
 
 out:
-- 
2.43.0