linux-kernel - Re: [PATCH] efi: Clarify Kconfig help for EFI

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Message-ID: <534B9C12.4050708@archlinux.org>
Date:	Mon, 14 Apr 2014 10:28:02 +0200
From:	Thomas Bächler <thomas@...hlinux.org>
To:	Ingo Molnar <mingo@...nel.org>,
	Matt Fleming <matt@...sole-pimps.org>
CC:	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Bächler <thomas@...hlinux.org>,
	Matt Fleming <matt.fleming@...el.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] efi: Clarify Kconfig help for EFI_MIXED

Am 14.04.2014 09:15, schrieb Ingo Molnar:
>>> Right, it is really that it is not possible to boot a mixed-mode kernel
>>> on its non-native firmware using the stub, since the stub itself can
>>> only be one way or the other.
>>
>> Yeah, my help text was a bit... unhelpful.
>>
>> CONFIG_EFI_MIXED does not introduce a regression of any sort, you can
>> enable it without worrying about that.
>>
>> All the boot configurations that used to work will continue to work.
>>
>> What I meant to say was that it isn't possible to use the EFI mixed 
>> *feature* (booting a 64-bit kernel with 32-bit firmware) with the 
>> EFI boot stub - so you can build support into your kernel but 
>> there's no way to make the CPU actually execute those code paths.
> 
> Same goes for booting a 32-bit kernel on 64-bit firmware, right?
> 

It seems that isn't implemented:

config EFI_MIXED
        bool "EFI mixed-mode support"
        depends on EFI_STUB && X86_64



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