linux-kernel - [RFC PATCH 14/56] x86/bugs: Reset GDS mitigations

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20251013143444.3999-15-david.kaplan@amd.com>
Date: Mon, 13 Oct 2025 09:34:02 -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: Alexander Graf <graf@...zon.com>, Boris Ostrovsky
	<boris.ostrovsky@...cle.com>, <linux-kernel@...r.kernel.org>
Subject: [RFC PATCH 14/56] x86/bugs: Reset GDS mitigations

Add function to reset GDS mitigations back to their boot-time defaults.

Signed-off-by: David Kaplan <david.kaplan@....com>
---
 arch/x86/kernel/cpu/bugs.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 112553058ccc..e765ac0b9240 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1182,6 +1182,18 @@ static void __init gds_apply_mitigation(void)
 	pr_info("%s\n", gds_strings[gds_mitigation]);
 }
 
+#ifdef CONFIG_DYNAMIC_MITIGATIONS
+static void gds_reset_mitigation(void)
+{
+	/* To cause the MSR bit to be cleared. */
+	gds_mitigation = GDS_MITIGATION_OFF;
+	if (x86_arch_cap_msr & ARCH_CAP_GDS_CTRL)
+		update_gds_msr();
+	gds_mitigation =  IS_ENABLED(CONFIG_MITIGATION_GDS) ?
+		GDS_MITIGATION_AUTO : GDS_MITIGATION_OFF;
+}
+#endif
+
 static int __init gds_parse_cmdline(char *str)
 {
 	if (!str)
@@ -3941,5 +3953,6 @@ void arch_cpu_reset_mitigations(void)
 	mmio_reset_mitigation();
 	srbds_reset_mitigation();
 	srso_reset_mitigation();
+	gds_reset_mitigation();
 }
 #endif
-- 
2.34.1