From: "H. Peter Anvin" Subject: Re: RFC: default CONFIG_EFI_STUB=y Date: Tue, 13 Aug 2013 12:06:26 -0700 Message-ID: <520A83B2.4010003@zytor.com> References: <52050985.9070107@zytor.com> <1376062345.2087.16.camel@dabdike.int.hansenpartnership.com> <52050D03.4030805@zytor.com> <520A7B48.3020304@zytor.com> <1376419410.3467.67.camel@dabdike.int.hansenpartnership.com> <520A8054.1030108@zytor.com> <1376420525.3467.70.camel@dabdike.int.hansenpartnership.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1376420525.3467.70.camel-sFMDBYUN5F8GjUHQrlYNx2Wm91YjaHnnhRte9Li2A+AAvxtiuMwx3w@public.gmane.org> Sender: linux-efi-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: James Bottomley Cc: Ingo Molnar , Thomas Gleixner , Linus Torvalds , "linux-efi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" , Linux Kernel Mailing List , Matt Fleming List-Id: linux-efi@vger.kernel.org On 08/13/2013 12:02 PM, James Bottomley wrote: > On Tue, 2013-08-13 at 11:52 -0700, H. Peter Anvin wrote: >> On 08/13/2013 11:43 AM, 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. >> >> We can boot with a bootloader in "skip stub" mode; no runtime services >> yet. > > So the bootloader has to do the 64->32 transition? > Currently, yes. >> We are working on making it possible to boot via a EFI stub in >> assisted mode (still needing a bootloader, but with the boot stub in the >> kernel.) >> >> Runtime services will be the last piece, obviously, but even that looks >> reasonably doable. > > So why not start with the working case (default to EFI on 64 bit) and > add in the mostly non-working case (default to EFI on 32 bit) when it > actually mostly works? We can do that, but I really hate making gratuitous differences between 32 and 64 bits... we have too many of those already. -hpa