From fb65e0dc7767b2a2408f91a39cdcd0f9dc1eeb8f Mon Sep 17 00:00:00 2001 From: Satoru Takeuchi Date: Thu, 14 Feb 2013 09:12:52 +0900 Subject: [PATCH] efi: Clear EFI_RUNTIME_SERVICES rather than EFI_BOOT by "noefi" boot parameter There was a serious problem in samsung-laptop that its platform driver is designed to run under BIOS and running under EFI can cause the machine to become bricked or can cause Machine Check Exceptions. Discussion about this problem: https://bugs.launchpad.net/ubuntu-cdimage/+bug/1040557 https://bugzilla.kernel.org/show_bug.cgi?id=47121 The patches to fix this problem: efi: Make 'efi_enabled' a function to query EFI facilities c285ff050870b3ad9eb4b9b56cd9a5103bdbe71b samsung-laptop: Disable on EFI hardware d68c9e06d778cb1bef8d5db4d34937d110dd91b4 Unfortunately this problem comes back again if users specify "noefi" option. This parameter clears EFI_BOOT and that driver continues to run even if running under EFI. Refer to the document, this parameter should clear EFI_RUNTIME_SERVICES instead. Documentation/kernel-parameters.txt: =============================================================================== ... noefi [X86] Disable EFI runtime services support. ... =============================================================================== Documentation/x86/x86_64/uefi.txt: =============================================================================== ... - If some or all EFI runtime services don't work, you can try following kernel command line parameters to turn off some or all EFI runtime services. noefi turn off all EFI runtime services ... =============================================================================== Signed-off-by: Satoru Takeuchi Link: http://lkml.kernel.org/r/511C2C04.2070108@jp.fujitsu.com Cc: Matt Fleming Cc: Signed-off-by: H. Peter Anvin --- arch/x86/platform/efi/efi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c index 77cf0090c0a3e..928bf837040a2 100644 --- a/arch/x86/platform/efi/efi.c +++ b/arch/x86/platform/efi/efi.c @@ -87,7 +87,7 @@ EXPORT_SYMBOL(efi_enabled); static int __init setup_noefi(char *arg) { - clear_bit(EFI_BOOT, &x86_efi_facility); + clear_bit(EFI_RUNTIME_SERVICES, &x86_efi_facility); return 0; } early_param("noefi", setup_noefi); -- 2.39.5