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

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Message-ID: <20250108202515.385902-36-david.kaplan@amd.com>
Date: Wed, 8 Jan 2025 14:25:15 -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 35/35] x86/pti: Add attack vector controls for pti

Disable PTI mitigation if user->kernel attack vector mitigations are
disabled.

Signed-off-by: David Kaplan <david.kaplan@....com>
---
 arch/x86/mm/pti.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index 5f0d579932c6..132840528d55 100644
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -38,6 +38,7 @@
 #include <asm/desc.h>
 #include <asm/sections.h>
 #include <asm/set_memory.h>
+#include <asm/bugs.h>
 
 #undef pr_fmt
 #define pr_fmt(fmt)     "Kernel/User page tables isolation: " fmt
@@ -94,7 +95,8 @@ void __init pti_check_boottime_disable(void)
 	if (pti_mode == PTI_FORCE_ON)
 		pti_print_if_secure("force enabled on command line.");
 
-	if (pti_mode == PTI_AUTO && !boot_cpu_has_bug(X86_BUG_CPU_MELTDOWN))
+	if (pti_mode == PTI_AUTO && (!boot_cpu_has_bug(X86_BUG_CPU_MELTDOWN) ||
+				     !cpu_mitigate_attack_vector(CPU_MITIGATE_USER_KERNEL)))
 		return;
 
 	setup_force_cpu_cap(X86_FEATURE_PTI);
-- 
2.34.1