linux-kernel - [tip: x86/bugs] x86/bugs: Add attack vector controls for MMIO

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Message-ID: <175225018142.406.15627389474878237417.tip-bot2@tip-bot2>
Date: Fri, 11 Jul 2025 16:09:41 -0000
From: "tip-bot2 for David Kaplan" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: David Kaplan <david.kaplan@....com>,
 "Borislav Petkov (AMD)" <bp@...en8.de>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: x86/bugs] x86/bugs: Add attack vector controls for MMIO

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     de6f0921ba49f5e07f57eb227dcb69ebb4776911
Gitweb:        https://git.kernel.org/tip/de6f0921ba49f5e07f57eb227dcb69ebb4776911
Author:        David Kaplan <david.kaplan@....com>
AuthorDate:    Mon, 07 Jul 2025 13:33:02 -05:00
Committer:     Borislav Petkov (AMD) <bp@...en8.de>
CommitterDate: Fri, 11 Jul 2025 17:56:40 +02:00

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>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Link: https://lore.kernel.org/20250707183316.1349127-8-david.kaplan@amd.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 438c482..39ff556 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -639,8 +639,12 @@ static void __init mmio_select_mitigation(void)
 	}
 
 	/* 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;
+	}
 
 	if (mmio_mitigation == MMIO_MITIGATION_OFF)
 		return;
@@ -655,7 +659,7 @@ static void __init mmio_select_mitigation(void)
 
 static void __init mmio_update_mitigation(void)
 {
-	if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA) || cpu_mitigations_off())
+	if (!boot_cpu_has_bug(X86_BUG_MMIO_STALE_DATA))
 		return;
 
 	if (verw_clear_cpu_buf_mitigation_selected)
@@ -703,7 +707,7 @@ static void __init mmio_apply_mitigation(void)
 	if (!(x86_arch_cap_msr & ARCH_CAP_FBSDP_NO))
 		static_branch_enable(&cpu_buf_idle_clear);
 
-	if (mmio_nosmt || cpu_mitigations_auto_nosmt())
+	if (mmio_nosmt || smt_mitigations == SMT_MITIGATIONS_ON)
 		cpu_smt_disable(false);
 }