linux-kernel - [RFC PATCH 17/56] x86/bugs: Reset TSA mitigations

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Message-ID: <20251013143444.3999-18-david.kaplan@amd.com>
Date: Mon, 13 Oct 2025 09:34:05 -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 17/56] x86/bugs: Reset TSA mitigations

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

Signed-off-by: David Kaplan <david.kaplan@....com>
---
 arch/x86/kernel/cpu/bugs.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index bf5de097e1a9..6a3e079a85fc 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1858,6 +1858,17 @@ static void __init tsa_apply_mitigation(void)
 	}
 }
 
+#ifdef CONFIG_DYNAMIC_MITIGATIONS
+static void tsa_reset_mitigation(void)
+{
+	setup_clear_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF);
+	setup_clear_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF_VM);
+	static_branch_disable(&cpu_buf_idle_clear);
+	tsa_mitigation =
+		IS_ENABLED(CONFIG_MITIGATION_TSA) ? TSA_MITIGATION_AUTO : TSA_MITIGATION_NONE;
+}
+#endif
+
 #undef pr_fmt
 #define pr_fmt(fmt)     "Spectre V2 : " fmt
 
@@ -3978,5 +3989,6 @@ void arch_cpu_reset_mitigations(void)
 	gds_reset_mitigation();
 	bhi_reset_mitigation();
 	its_reset_mitigation();
+	tsa_reset_mitigation();
 }
 #endif
-- 
2.34.1