linux-kernel - [PATCH v5 17/20] x86/bugs: Add attack vector controls for SRSO

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Message-ID: <20250509162839.3057217-18-david.kaplan@amd.com>
Date: Fri, 9 May 2025 11:28:36 -0500
From: David Kaplan <david.kaplan@....com>
To: Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>,
	Peter Zijlstra <peterz@...radead.org>, Josh Poimboeuf <jpoimboe@...nel.org>,
	Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>, Ingo Molnar
	<mingo@...hat.com>, Dave Hansen <dave.hansen@...ux.intel.com>,
	<x86@...nel.org>, "H . Peter Anvin" <hpa@...or.com>
CC: <linux-kernel@...r.kernel.org>
Subject: [PATCH v5 17/20] x86/bugs: Add attack vector controls for SRSO

Use attack vector controls to determine if SRSO mitigation is required.

Signed-off-by: David Kaplan <david.kaplan@....com>
---
 arch/x86/kernel/cpu/bugs.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 19a176369b22..55b0658562c0 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2840,14 +2840,19 @@ static void __init srso_select_mitigation(void)
 {
 	bool has_microcode;
 
-	if (!boot_cpu_has_bug(X86_BUG_SRSO) || cpu_mitigations_off())
+	if (!boot_cpu_has_bug(X86_BUG_SRSO)) {
 		srso_mitigation = SRSO_MITIGATION_NONE;
-
-	if (srso_mitigation == SRSO_MITIGATION_NONE)
 		return;
+	}
 
-	if (srso_mitigation == SRSO_MITIGATION_AUTO)
-		srso_mitigation = SRSO_MITIGATION_SAFE_RET;
+	if (srso_mitigation == SRSO_MITIGATION_AUTO) {
+		if (should_mitigate_vuln(X86_BUG_SRSO)) {
+			srso_mitigation = SRSO_MITIGATION_SAFE_RET;
+		} else {
+			srso_mitigation = SRSO_MITIGATION_NONE;
+			return;
+		}
+	}
 
 	has_microcode = boot_cpu_has(X86_FEATURE_IBPB_BRTYPE);
 	if (has_microcode) {
@@ -2909,7 +2914,7 @@ static void __init srso_update_mitigation(void)
 	    boot_cpu_has(X86_FEATURE_IBPB_BRTYPE))
 		srso_mitigation = SRSO_MITIGATION_IBPB;
 
-	if (boot_cpu_has_bug(X86_BUG_SRSO) && !cpu_mitigations_off())
+	if (boot_cpu_has_bug(X86_BUG_SRSO))
 		pr_info("%s\n", srso_strings[srso_mitigation]);
 }
 
-- 
2.34.1