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

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

[Matt Fleming]

From: Matt Fleming <matt.fleming@intel.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@gmail.com>
Cc: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>
Cc: H. Peter Anvin <hpa@linux.intel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Matt Fleming <matt.fleming@intel.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

Re: [PATCH] x86, efi: Make "noefi" really disable EFI runtime serivces

[Satoru Takeuchi]

Hi Matt,

(2013/02/21 5:36), Matt Fleming wrote:
> From: Matt Fleming <matt.fleming-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> 
> 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.

Sorry, my patch was imperfect. This patch looks good to me.

Reviewed-by: Satoru Takeuchi <takeuchi_satoru-+CUm20s59erQFUHtdCDX3A@public.gmane.org>

Thanks,
Satoru

> 
> Reported-by: Walt Nelson Jr <walt0924-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> Cc: Satoru Takeuchi <takeuchi_satoru-+CUm20s59erQFUHtdCDX3A@public.gmane.org>
> Cc: H. Peter Anvin <hpa-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>
> Cc: <stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
> Signed-off-by: Matt Fleming <matt.fleming-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> ---
>  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);
>  	}
> 

Re: [PATCH] x86, efi: Make "noefi" really disable EFI runtime serivces

[H. Peter Anvin]

On 02/20/2013 03:46 PM, Satoru Takeuchi wrote:
> 
> Sorry, my patch was imperfect. This patch looks good to me.
> 

Perfection is something very rarely achieved.  That's why we work with
gradual improvements.

	-hpa