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

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Message-ID: <175225017109.406.2846188212042963198.tip-bot2@tip-bot2>
Date: Fri, 11 Jul 2025 16:09:31 -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 ITS

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

Commit-ID:     0cdd2c4f35cf9bb9466b36724b658d11ff453f04
Gitweb:        https://git.kernel.org/tip/0cdd2c4f35cf9bb9466b36724b658d11ff453f04
Author:        David Kaplan <david.kaplan@....com>
AuthorDate:    Mon, 07 Jul 2025 13:33:13 -05:00
Committer:     Borislav Petkov (AMD) <bp@...en8.de>
CommitterDate: Fri, 11 Jul 2025 17:56:41 +02:00

x86/bugs: Add attack vector controls for ITS

Use attack vector controls to determine if ITS 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/20250707183316.1349127-19-david.kaplan@amd.com
---
 arch/x86/kernel/cpu/bugs.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index eef6ccd..f41d871 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1518,13 +1518,17 @@ early_param("indirect_target_selection", its_parse_cmdline);
 
 static void __init its_select_mitigation(void)
 {
-	if (!boot_cpu_has_bug(X86_BUG_ITS) || cpu_mitigations_off()) {
+	if (!boot_cpu_has_bug(X86_BUG_ITS)) {
 		its_mitigation = ITS_MITIGATION_OFF;
 		return;
 	}
 
-	if (its_mitigation == ITS_MITIGATION_AUTO)
-		its_mitigation = ITS_MITIGATION_ALIGNED_THUNKS;
+	if (its_mitigation == ITS_MITIGATION_AUTO) {
+		if (should_mitigate_vuln(X86_BUG_ITS))
+			its_mitigation = ITS_MITIGATION_ALIGNED_THUNKS;
+		else
+			its_mitigation = ITS_MITIGATION_OFF;
+	}
 
 	if (its_mitigation == ITS_MITIGATION_OFF)
 		return;
@@ -1555,12 +1559,13 @@ static void __init its_select_mitigation(void)
 
 static void __init its_update_mitigation(void)
 {
-	if (!boot_cpu_has_bug(X86_BUG_ITS) || cpu_mitigations_off())
+	if (!boot_cpu_has_bug(X86_BUG_ITS))
 		return;
 
 	switch (spectre_v2_enabled) {
 	case SPECTRE_V2_NONE:
-		pr_err("WARNING: Spectre-v2 mitigation is off, disabling ITS\n");
+		if (its_mitigation != ITS_MITIGATION_OFF)
+			pr_err("WARNING: Spectre-v2 mitigation is off, disabling ITS\n");
 		its_mitigation = ITS_MITIGATION_OFF;
 		break;
 	case SPECTRE_V2_RETPOLINE: