x86, efi: Make "noefi" really disable EFI runtime serivces

commit 1de63d60cd5b ("efi: Clear EFI_RUNTIME_SERVICES rather than
EFI_BOOT by "noefi" boot parameter") attempted to make "noefi" true to
its documentation and disable EFI runtime services to prevent the
bricking bug described in commit e0094244e41c ("samsung-laptop:
Disable on EFI hardware"). However, it's not possible to clear
EFI_RUNTIME_SERVICES from an early param function because
EFI_RUNTIME_SERVICES is set in efi_init() *after* parse_early_param().

This resulted in "noefi" effectively becoming a no-op and no longer
providing users with a way to disable EFI, which is bad for those
users that have buggy machines.

Reported-by: Walt Nelson Jr <walt0924@gmail.com>
Cc: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Link: http://lkml.kernel.org/r/1361392572-25657-1-git-send-email-matt@console-pimps.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 928bf837040a..e2cd38ffc406 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -85,9 +85,10 @@ int efi_enabled(int facility)
 }
 EXPORT_SYMBOL(efi_enabled);
 
+static bool disable_runtime = false;
 static int __init setup_noefi(char *arg)
 {
-        clear_bit(EFI_RUNTIME_SERVICES, &x86_efi_facility);
+        disable_runtime = true;
         return 0;
 }
 early_param("noefi", setup_noefi);
@@ -734,7 +735,7 @@ void __init efi_init(void)
         if (!efi_is_native())
                 pr_info("No EFI runtime due to 32/64-bit mismatch with kernel\n");
         else {
-                if (efi_runtime_init())
+                if (disable_runtime || efi_runtime_init())
                         return;
                 set_bit(EFI_RUNTIME_SERVICES, &x86_efi_facility);
         }