[tip: x86/cpu] x86/cpu: Remove LASS restriction on EFI

[tip-bot2 for Sohil Mehta]

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

Commit-ID:     68400c1aaf02636a97c45ba198110b66feb270a9
Gitweb:        https://git.kernel.org/tip/68400c1aaf02636a97c45ba198110b66feb270a9
Author:        Sohil Mehta <sohil.mehta@xxxxxxxxx>
AuthorDate:    Tue, 20 Jan 2026 15:47:30 -08:00
Committer:     Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
CommitterDate: Tue, 03 Mar 2026 09:49:45 -08:00

x86/cpu: Remove LASS restriction on EFI

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@xxxxxxxxx>
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Tested-by: Tony Luck <tony.luck@xxxxxxxxx>
Tested-by: Maciej Wieczor-Retman <maciej.wieczor-retman@xxxxxxxxx>
Link: https://patch.msgid.link/20260120234730.2215498-4-sohil.mehta@xxxxxxxxx
---
 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 8c56d59..3557f0e 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)