linux-kernel - Re: [PATCH] x86: efi: Turn off efi_enabled after setup on mixed fw/kernel

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Date:	Mon, 20 Aug 2012 10:56:41 +0100
From:	Matt Fleming <matt.fleming@...el.com>
To:	Olof Johansson <olof@...om.net>
Cc:	hpa@...or.com, linux-kernel@...r.kernel.org, mk@....su,
	Marko Kohtala <marko.kohtala@...il.com>,
	Matthew Garrett <mjg@...hat.com>
Subject: Re: [PATCH] x86: efi: Turn off efi_enabled after setup on mixed
 fw/kernel

On Sun, 2012-08-19 at 14:48 -0700, Olof Johansson wrote:
> When 32-bit EFI is used with 64-bit kernel (or vice versa), turn off
> efi_enabled once setup is done. Beyond setup, it is normally used to
> determine if runtime services are available and we will have none.
> 
> This will resolve issues stemming from efivars modprobe panicking on a
> 32/64-bit setup, as well as some reboot issues on similar setups.
> 
> Signed-off-by: Olof Johansson <olof@...om.net>
> Cc: stable@...nel.org # 3.4 and 3.5
> Cc: Matt Fleming <matt.fleming@...el.com>
> Cc: Matthew Garrett <mjg@...hat.com>
> ---
>  arch/x86/kernel/setup.c     | 11 +++++++++++
>  arch/x86/platform/efi/efi.c | 14 ++++++++------
>  2 files changed, 19 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index f4b9b80..dad38ac 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -1034,6 +1034,17 @@ void __init setup_arch(char **cmdline_p)
>  	mcheck_init();
>  
>  	arch_init_ideal_nops();
> +
> +#ifdef CONFIG_EFI
> +	/* Once setup is done above, disable efi_enabled on mismatched
> +	 * firmware/kernel archtectures since there is no support for
> +	 * runtime services.
> +	 */
> +	if (IS_ENABLED(CONFIG_X86_64) ^ efi_64bit) {
> +		pr_info("efi: Setup done, disabling due to 32/64-bit mismatch\n");
> +		efi_enabled = 0;
> +	}
> +#endif
>  }

Is there a reason we can't just disable efi_enabled at the end of
efi_init() if we're non-native, rather than having this chunk of code
here?

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