linux-kernel - [PATCH] x86, efi: Make "noefi" really disable EFI runtime serivces

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Message-Id: <1361392572-25657-1-git-send-email-matt@console-pimps.org>
Date:	Wed, 20 Feb 2013 20:36:12 +0000
From:	Matt Fleming <matt@...sole-pimps.org>
To:	"H. Peter Anvin" <hpa@...ux.intel.com>
Cc:	linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
	Matt Fleming <matt.fleming@...el.com>,
	Satoru Takeuchi <takeuchi_satoru@...fujitsu.com>,
	<stable@...r.kernel.org>
Subject: [PATCH] x86, efi: Make "noefi" really disable EFI runtime serivces

From: Matt Fleming <matt.fleming@...el.com>

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@...il.com>
Cc: Satoru Takeuchi <takeuchi_satoru@...fujitsu.com>
Cc: H. Peter Anvin <hpa@...ux.intel.com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Matt Fleming <matt.fleming@...el.com>
---
 arch/x86/platform/efi/efi.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 928bf83..e2cd38f 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);
 	}
-- 
1.7.11.7

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