linux-kernel - Re: RFC: default CONFIG_EFI

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Message-ID: <52050D03.4030805@zytor.com>
Date:	Fri, 09 Aug 2013 08:38:43 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	James Bottomley <James.Bottomley@...senPartnership.com>
CC:	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Matt Fleming <matt.fleming@...el.com>
Subject: Re: RFC: default CONFIG_EFI_STUB=y

On 08/09/2013 08:32 AM, James Bottomley wrote:
> On Fri, 2013-08-09 at 08:23 -0700, H. Peter Anvin wrote:
>> I would like to change the defaults for CONFIG_EFI and CONFIG_EFI_STUB
>> to y.  There is little reason to omit this since EFI now is a
>> significant percentage of all systems.
> 
> You didn't actually attach the patch, but I presume this is for 64 bit
> compiles on x86 only?  We still have significant problems getting 64 bit
> EFI to interact with 32 bit kernels, so I don't believe we should enable
> CONFIG_EFI globally for all of x86.
> 

Well, it doesn't *solve* the problem with cross-mode, but it should work
as-is for EFI32->32-bit kernel and EFI64->64-bit kernel.  For the
cross-mode kernels they will simply not do anything.

Either way, nothing bad should come from it.  The worst thing that will
happen is that the kernel says "I don't have any EFI that I recognize."

Cross-mode support will always require a secondary bootloader (since as
far as I know there is no concept of "fat binaries" for EFI), but Matt
Fleming is working on genuine cross-mode support for both the boot stub
and (eventually) run time support.

	-hpa

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