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From: Sohil Mehta <sohil.mehta@intel.com>
To: x86@kernel.org, Dave Hansen <dave.hansen@linux.intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Ard Biesheuvel <ardb@kernel.org>
Cc: "H . Peter Anvin" <hpa@zytor.com>,
	Andy Lutomirski <luto@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	"Kirill A . Shutemov" <kas@kernel.org>,
	Sohil Mehta <sohil.mehta@intel.com>,
	Rick Edgecombe <rick.p.edgecombe@intel.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Tony Luck <tony.luck@intel.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org
Subject: [PATCH v2 3/3] x86/cpu: Remove LASS restriction on EFI
Date: Tue, 20 Jan 2026 15:47:30 -0800	[thread overview]
Message-ID: <20260120234730.2215498-4-sohil.mehta@intel.com> (raw)
In-Reply-To: <20260120234730.2215498-1-sohil.mehta@intel.com>

The initial LASS enabling has been deferred to much later during boot,
and EFI runtime services now run with LASS temporarily disabled. This
removes LASS from the path of all EFI services.

Remove the LASS restriction on EFI config, as the two can now coexist.

Signed-off-by: Sohil Mehta <sohil.mehta@intel.com>
---
v2:
 - No change
---
 arch/x86/kernel/cpu/common.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index cefd0722e6cc..5833849f0b52 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -415,14 +415,9 @@ static __always_inline void setup_lass(struct cpuinfo_x86 *c)
 	 * Legacy vsyscall page access causes a #GP when LASS is active.
 	 * Disable LASS because the #GP handler doesn't support vsyscall
 	 * emulation.
-	 *
-	 * Also disable LASS when running under EFI, as some runtime and
-	 * boot services rely on 1:1 mappings in the lower half.
 	 */
-	if (IS_ENABLED(CONFIG_X86_VSYSCALL_EMULATION) ||
-	    IS_ENABLED(CONFIG_EFI)) {
+	if (IS_ENABLED(CONFIG_X86_VSYSCALL_EMULATION))
 		setup_clear_cpu_cap(X86_FEATURE_LASS);
-	}
 }
 
 static int enable_lass(unsigned int cpu)
-- 
2.43.0


  parent reply	other threads:[~2026-01-20 23:49 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-01-20 23:47 [PATCH v2 0/3] x86: Extend LASS support to EFI configurations Sohil Mehta
2026-01-20 23:47 ` [PATCH v2 1/3] x86/cpu: Defer LASS enabling until userspace comes up Sohil Mehta
2026-02-19 21:02   ` Sohil Mehta
2026-03-03 17:41     ` Dave Hansen
2026-03-03 23:59   ` [tip: x86/cpu] " tip-bot2 for Sohil Mehta
2026-01-20 23:47 ` [PATCH v2 2/3] x86/efi: Disable LASS while executing runtime services Sohil Mehta
2026-03-03 23:59   ` [tip: x86/cpu] " tip-bot2 for Sohil Mehta
2026-01-20 23:47 ` Sohil Mehta [this message]
2026-03-03 23:59   ` [tip: x86/cpu] x86/cpu: Remove LASS restriction on EFI tip-bot2 for Sohil Mehta
2026-02-04 17:08 ` [PATCH v2 0/3] x86: Extend LASS support to EFI configurations Maciej Wieczor-Retman
2026-02-05 17:47 ` Luck, Tony
2026-02-24 18:45 ` Sohil Mehta
2026-02-24 18:49   ` Ard Biesheuvel
2026-03-03 17:42   ` Dave Hansen

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