[coreboot] SeaBIOS debug output

Jordan Crouse jordan.crouse at amd.com
Wed Jul 16 21:55:23 CEST 2008

On 16/07/08 12:43 -0600, Myles Watson wrote:
> On Fri, Jul 11, 2008 at 12:51 PM, Kevin O'Connor <kevin at koconnor.net> wrote:
> > On Fri, Jul 11, 2008 at 07:58:35PM +0200, Carl-Daniel Hailfinger wrote:
> >> Can seabios somehow complement x86emu as a way to let certain
> >> problematic VBIOS images run?
> >
> > If you mean run seabios under x86emu - I'm not sure.  Seabios
> > currently does its initialization in 32bit mode which x86emu may not
> > like.
> >
> > If you mean using seabios to implement the option rom scan - then yes,
> > I think this is what Stefan suggested and Zhang Rui is working on.  If
> > I understand correctly, they want to load the seabios blob into ram,
> > have seabios do its init, run the option roms, and then jump back to
> > coreboot for the rest of the boot.  Presumably, coreboot would also
> > use seabios to boot the machine if the user wanted that.
> >
> > The thing to be careful of here is making sure coreboot and seabios
> > don't stomp on each other.  This may not be such a big deal - seabios
> > doesn't currently write to any ram above 1MiB - if coreboot didn't
> > write to any ram below 1MiB after launching seabios then maybe it
> > would work.
> I for one don't understand what needs to be done in coreboot after the
> option ROM scans.  It seems like it would help us discuss the possible
> solutions if we could enumerate that.
> I don't think the Coreboot->SeaBIOS->Coreboot->Payload route means
> that SeaBIOS has to return to Coreboot.  It seems like Coreboot can
> load whatever should come after SeaBIOS into RAM and have SeaBIOS jump
> there.  

This seems like semantics to me - the jmp will be to an arbitrary
address - it doesn't really matter if it goes back to coreboot or
if it goes to the payload.  If it jumped to the payload, SeaBIOS
will have to be told _where_ to jump anyway, since the payload can
live anywhere.  All we really need to do is set up an interface to pass a
address to SeaBIOS, and then its up to coreboot to figure out what
they want to do after SeaBIOS is done.


Jordan Crouse
Systems Software Development Engineer 
Advanced Micro Devices, Inc.

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