linux-kernel - [PATCH v4 24/36] x86/bugs: Add attack vector controls for rfds

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Message-ID: <20250310164023.779191-25-david.kaplan@amd.com>
Date: Mon, 10 Mar 2025 11:40:11 -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>, Brendan Jackman <jackmanb@...gle.com>,
	Derek Manwaring <derekmn@...zon.com>
Subject: [PATCH v4 24/36] x86/bugs: Add attack vector controls for rfds

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

Signed-off-by: David Kaplan <david.kaplan@....com>
---
 arch/x86/kernel/cpu/bugs.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index ba7c2a1ea98f..32f850c80b86 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -712,13 +712,20 @@ static bool __init rfds_has_ucode(void)
 
 static void __init rfds_select_mitigation(void)
 {
-	if (!boot_cpu_has_bug(X86_BUG_RFDS) || cpu_mitigations_off()) {
+	if (!boot_cpu_has_bug(X86_BUG_RFDS)) {
 		rfds_mitigation = RFDS_MITIGATION_OFF;
 		return;
 	}
 
-	if (rfds_mitigation == RFDS_MITIGATION_AUTO)
-		rfds_mitigation = RFDS_MITIGATION_VERW;
+	if (rfds_mitigation == RFDS_MITIGATION_AUTO) {
+		if (should_mitigate_vuln(X86_BUG_RFDS))
+			rfds_mitigation = RFDS_MITIGATION_VERW;
+		else
+			rfds_mitigation = RFDS_MITIGATION_OFF;
+	}
+
+	if (rfds_mitigation == RFDS_MITIGATION_OFF)
+		return;
 
 	if (rfds_has_ucode())
 		verw_mitigation_selected = true;
@@ -726,7 +733,7 @@ static void __init rfds_select_mitigation(void)
 
 static void __init rfds_update_mitigation(void)
 {
-	if (!boot_cpu_has_bug(X86_BUG_RFDS) || cpu_mitigations_off())
+	if (!boot_cpu_has_bug(X86_BUG_RFDS))
 		return;
 
 	if (verw_mitigation_selected)
-- 
2.34.1