Re: RFC: default CONFIG_EFI_STUB=y

[James Bottomley <James.Bottomley@HansenPartnership.com>]

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?

>   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?

James