linux-kernel - [PATCH v3 24/35] x86/bugs: Add attack vector controls for mmio

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Message-ID: <20250108202515.385902-25-david.kaplan@amd.com>
Date: Wed, 8 Jan 2025 14:25:04 -0600
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 v3 24/35] x86/bugs: Add attack vector controls for mmio

Use attack vectors controls to determine if mmio mitigation is required.

Signed-off-by: David Kaplan <david.kaplan@....com>
---
 arch/x86/kernel/cpu/bugs.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index af5aaa0397c7..4249a1f1524c 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -676,9 +676,12 @@ static void __init mmio_select_mitigation(void)
 		return;
 
 	/* Microcode will be checked in mmio_update_mitigation(). */
-	if (mmio_mitigation == MMIO_MITIGATION_AUTO)
-		mmio_mitigation = MMIO_MITIGATION_VERW;
-
+	if (mmio_mitigation == MMIO_MITIGATION_AUTO) {
+		if (should_mitigate_vuln(X86_BUG_MMIO_STALE_DATA))
+			mmio_mitigation = MMIO_MITIGATION_VERW;
+		else
+			mmio_mitigation = MMIO_MITIGATION_OFF;
+	}
 }
 
 static void __init mmio_update_mitigation(void)
@@ -739,7 +742,8 @@ static void __init mmio_apply_mitigation(void)
 	if (!(x86_arch_cap_msr & ARCH_CAP_FBSDP_NO))
 		static_branch_enable(&mds_idle_clear);
 
-	if (mmio_nosmt || cpu_mitigations_auto_nosmt())
+	if (mmio_nosmt || cpu_mitigations_auto_nosmt() ||
+	    cpu_mitigate_attack_vector(CPU_MITIGATE_CROSS_THREAD))
 		cpu_smt_disable(false);
 }
 
-- 
2.34.1