[SeaBIOS] varlow/extrastack vs code

Dr. David Alan Gilbert dgilbert at redhat.com
Tue Feb 14 19:28:55 CET 2017


* Gerd Hoffmann (kraxel at redhat.com) wrote:
>   Hi,
> 
> > Do you mean a workaround for the (historically lacking) emulation of the
> > PAM chipset registers? PAM emulation has been correct for quite a while
> > now in QEMU, as far as I can tell.
> > 
> > (Sorry if I'm completely off.)
> 
> That was the first thing coming to my mind too.
> 
> So, yes, recent qemu versions should not suffer from that issue.
> But seabios wants to be able to run on old qemu versions too, so they
> can't be completely ignored ...
> 
> Maybe fixing things on modern qemu is easier if we add a compile time
> option for backward compatibility with old qemu versions?
> 
> At least for qemu this would work fine.  We have two different seabios
> binaries anyway, because at some point seabios didn't fit into 128k any
> more.  So we have one 128k bios, for backward compatibility, and with
> support for features added only recently to qemu turned off to make it
> fit.  And one full-featured 256k bios version.  Only the 128k version
> needs support for old qemu versions without proper PAM emulation.

But of course that's the one that's actually broken in this case!

Dave

> cheers,
>   Gerd
> 
--
Dr. David Alan Gilbert / dgilbert at redhat.com / Manchester, UK



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