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

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Message-ID: <50880E59.3000309@canonical.com>
Date:	Wed, 24 Oct 2012 17:50:49 +0200
From:	Maarten Lankhorst <maarten.lankhorst@...onical.com>
To:	Olof Johansson <olof@...om.net>
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

Op 24-10-12 17:21, Olof Johansson schreef:
> 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.
>
Ack
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