linux-kernel - [PATCH v10 04/15] x86/cpu: Set LASS CR4 bit as pinning sensitive

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Message-ID: <20251007065119.148605-5-sohil.mehta@intel.com>
Date: Mon,  6 Oct 2025 23:51:08 -0700
From: Sohil Mehta <sohil.mehta@...el.com>
To: x86@...nel.org,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>
Cc: Jonathan Corbet <corbet@....net>,
	"H . Peter Anvin" <hpa@...or.com>,
	Andy Lutomirski <luto@...nel.org>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ard Biesheuvel <ardb@...nel.org>,
	"Kirill A . Shutemov" <kas@...nel.org>,
	Sohil Mehta <sohil.mehta@...el.com>,
	Xin Li <xin@...or.com>,
	David Woodhouse <dwmw@...zon.co.uk>,
	Sean Christopherson <seanjc@...gle.com>,
	Rick Edgecombe <rick.p.edgecombe@...el.com>,
	Vegard Nossum <vegard.nossum@...cle.com>,
	Andrew Cooper <andrew.cooper3@...rix.com>,
	David Laight <david.laight.linux@...il.com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Kees Cook <kees@...nel.org>,
	Tony Luck <tony.luck@...el.com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-efi@...r.kernel.org
Subject: [PATCH v10 04/15] x86/cpu: Set LASS CR4 bit as pinning sensitive

From: Yian Chen <yian.chen@...el.com>

Security features such as LASS are not expected to be disabled once
initialized. Add LASS to the CR4 pinned mask.

Signed-off-by: Yian Chen <yian.chen@...el.com>
Signed-off-by: Sohil Mehta <sohil.mehta@...el.com>
---
v10:
 - No change.
---
 arch/x86/kernel/cpu/common.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index c7d3512914ca..61ab332eaf73 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -403,7 +403,8 @@ static __always_inline void setup_umip(struct cpuinfo_x86 *c)
 
 /* These bits should not change their value after CPU init is finished. */
 static const unsigned long cr4_pinned_mask = X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_UMIP |
-					     X86_CR4_FSGSBASE | X86_CR4_CET | X86_CR4_FRED;
+					     X86_CR4_FSGSBASE | X86_CR4_CET | X86_CR4_FRED |
+					     X86_CR4_LASS;
 static DEFINE_STATIC_KEY_FALSE_RO(cr_pinning);
 static unsigned long cr4_pinned_bits __ro_after_init;
 
-- 
2.43.0