[SeaBIOS] varlow/extrastack vs code

[Gerd Hoffmann]

  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.

cheers,
  Gerd