linux-kernel - Re: [PATCH v2] x86: efi: Turn off efi_enabled after setup on mixed fw/kernel

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Date:	Wed, 24 Oct 2012 08:21:36 -0700
From:	Olof Johansson <olof@...om.net>
To:	Maarten Lankhorst <maarten.lankhorst@...onical.com>
Cc:	matt@...sole-pimps.org, hpa@...or.com,
	linux-kernel@...r.kernel.org, marko.kohtala@...il.com,
	Matthew Garrett <mjg@...hat.com>
Subject: Re: [PATCH v2] x86: efi: Turn off efi_enabled after setup on mixed fw/kernel

Hi,

On Wed, Oct 24, 2012 at 1:40 AM, Maarten Lankhorst
<maarten.lankhorst@...onical.com> wrote:
> Op 24-10-12 08:24, Olof Johansson schreef:
>> 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.
>>
>> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=45991
>>
>> Reported-by: Marko Kohtala <marko.kohtala@...il.com>
>> Reported-by: Maxim Kammerer <mk@....su>
>> Signed-off-by: Olof Johansson <olof@...om.net>
>> Cc: stable@...nel.org # 3.4 - 3.6
>> Cc: Matthew Garrett <mjg@...hat.com>
>> Cc: Maarten Lankhorst <maarten.lankhorst@...onical.com>
>> ---
>>
>> v2: rebase due to context diffs, and simplified efi_is_native() logic.
>>
>>  arch/x86/kernel/setup.c     | 11 +++++++++++
>>  arch/x86/platform/efi/efi.c | 16 +++++++++-------
>>  2 files changed, 20 insertions(+), 7 deletions(-)
>>
>> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
>> index 468e98d..ea2c587 100644
>> --- a/arch/x86/kernel/setup.c
>> +++ b/arch/x86/kernel/setup.c
>> @@ -1048,6 +1048,17 @@ void __init setup_arch(char **cmdline_p)
>>       arch_init_ideal_nops();
>>
>>       register_refined_jiffies(CLOCK_TICK_RATE);
>> +
>> +#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
>>  }
>
> Won't this give a spurious warning if it's already disabled?

Ah, of course, my bad. v3 forthcoming.

> And it should probably be moved to before the vga con setup, else it seems you
> might not get a vga console when efifb is not used. Unless that's intentional,
> but in that case please change the commit message to reflect that. :-)

Hmm. I think the current logic and flow is valid -- it's likely a bad
idea to enable VGA console if the memory isn't set aside in the memory
map, since that possibly means that EFI didn't POST graphics for VGA
text mode in the first place.

> With those issues fixed in next version.
>
> Acked-by: Maarten Lankhorst <maarten.lankhorst@...onical.com>

Please confirm if you agree with my reasoning above, I'll post v3
right after if so.

Thanks,

-Olof
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