linux-kernel - Re: RFC: default CONFIG_EFI

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Message-ID: <20130815051509.GB1933@srcf.ucam.org>
Date:	Thu, 15 Aug 2013 06:15:09 +0100
From:	Matthew Garrett <mjg59@...f.ucam.org>
To:	James Bottomley <James.Bottomley@...senPartnership.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, 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 Tue, Aug 13, 2013 at 11:43:30AM -0700, James Bottomley wrote:

> Can we actually boot a 32 bit kernel on an EFI64 system?  The last time
> I tried on my Secure Boot SDV it wouldn't work; the problem is getting
> someting in the transfer of control path to boot the processor back to
> 32 bit mode.

In theory, as long as you jump to the 32-bit entry point having already 
set the cpu to that mode. The linux command in grub2 ought to do that.

-- 
Matthew Garrett | mjg59@...f.ucam.org
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