linux-kernel - [PATCH v7 19/22] x86/bugs: Add attack vector controls for TSA

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Message-ID: <20250709155844.3279471-1-david.kaplan@amd.com>
Date: Wed, 9 Jul 2025 10:58:44 -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 v7 19/22] x86/bugs: Add attack vector controls for TSA

Use attack vector controls to determine which TSA mitigation to use.

Signed-off-by: David Kaplan <david.kaplan@....com>
---
 arch/x86/kernel/cpu/bugs.c | 26 ++++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index f41d871f0622..e02b232fcc6e 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1657,28 +1657,38 @@ early_param("tsa", tsa_parse_cmdline);
 
 static void __init tsa_select_mitigation(void)
 {
-	if (cpu_mitigations_off() || !boot_cpu_has_bug(X86_BUG_TSA)) {
+	if (!boot_cpu_has_bug(X86_BUG_TSA)) {
 		tsa_mitigation = TSA_MITIGATION_NONE;
 		return;
 	}
 
+	if (tsa_mitigation == TSA_MITIGATION_AUTO) {
+		if (cpu_attack_vector_mitigated(CPU_MITIGATE_USER_KERNEL) ||
+		    cpu_attack_vector_mitigated(CPU_MITIGATE_USER_USER)) {
+			if (cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_HOST) ||
+			    cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_GUEST))
+				tsa_mitigation = TSA_MITIGATION_FULL;
+			else
+				tsa_mitigation = TSA_MITIGATION_USER_KERNEL;
+		} else if (cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_HOST) ||
+			   cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_GUEST)) {
+			tsa_mitigation = TSA_MITIGATION_VM;
+		} else {
+			tsa_mitigation = TSA_MITIGATION_NONE;
+		}
+	}
+
 	if (tsa_mitigation == TSA_MITIGATION_NONE)
 		return;
 
-	if (!boot_cpu_has(X86_FEATURE_VERW_CLEAR)) {
+	if (!boot_cpu_has(X86_FEATURE_VERW_CLEAR))
 		tsa_mitigation = TSA_MITIGATION_UCODE_NEEDED;
-		goto out;
-	}
-
-	if (tsa_mitigation == TSA_MITIGATION_AUTO)
-		tsa_mitigation = TSA_MITIGATION_FULL;
 
 	/*
 	 * No need to set verw_clear_cpu_buf_mitigation_selected - it
 	 * doesn't fit all cases here and it is not needed because this
 	 * is the only VERW-based mitigation on AMD.
 	 */
-out:
 	pr_info("%s\n", tsa_strings[tsa_mitigation]);
 }
 
-- 
2.34.1