[tip:x86/urgent] efi: Clear EFI_RUNTIME_SERVICES rather than EFI_BOOT by "noefi" boot parameter

From: tip-bot for Satoru Takeuchi
Date: Wed Feb 13 2013 - 23:54:35 EST

Commit-ID: 1de63d60cd5b0d33a812efa455d5933bf1564a51
Gitweb: http://git.kernel.org/tip/1de63d60cd5b0d33a812efa455d5933bf1564a51
Author: Satoru Takeuchi <takeuchi_satoru@xxxxxxxxxxxxxx>
AuthorDate: Thu, 14 Feb 2013 09:12:52 +0900
Committer: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
CommitDate: Wed, 13 Feb 2013 17:24:11 -0800

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:

The patches to fix this problem:
efi: Make 'efi_enabled' a function to query EFI facilities

samsung-laptop: Disable on EFI hardware

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

noefi [X86] Disable EFI runtime services support.

- 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
noefi turn off all EFI runtime services

Signed-off-by: Satoru Takeuchi <takeuchi_satoru@xxxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/511C2C04.2070108@xxxxxxxxxxxxxx
Cc: Matt Fleming <matt.fleming@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
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 77cf009..928bf83 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);
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