[SeaBIOS] S3 resume is broken on QEMU

[Kevin O'Connor]

On Fri, Jan 20, 2012 at 01:50:15PM +0200, Gleb Natapov wrote:
> On Thu, Jan 19, 2012 at 08:40:45PM -0500, Kevin O'Connor wrote:
> > Further, no spec I've seen says an option rom must handle being
> > executed a second time.  The option rom can self modify - re-running a
> > modified rom may crash it.  Thinking about this further, the vgabios
> > in the seabios repo wont handle being executed twice properly (which,
> > of course, should be fixed).
> > 
> Not sure how thing works on real HW, but on QEMU S3 actually invokes HW
> reset. The same reset that is done on reboot, so option rom should be
> reset to its pristine state. I expect that on real HW things should be
> similar if device powered down on S3.

I'm 99% sure that wont work.  Option roms have to be copied from PCI
bars to low memory.  If seabios copies the option rom again (to reset
its state) then all option roms would need to be copied (the initial
option rom size could be larger than the final option rom size).
Running all option roms again is surely going to break something.

> > To be clear, I really don't know the exact interactions between an off
> > the shelf BIOS and a "real world" vga bios on resume.  If someone can
> > find a spec or document clarifying that - I'd be happy to conform to
> > it.
> > 
> I am not asking to change how Seabios works on real HW. What it does
> currently on real HW has a lot of sense and models behaviour of real
> BIOSes as far as I can tell.

I understand your point about requesting QEMU specific code.  I really
prefer to keep things general where ever possible, however.  I think
both projects are better off if the most code possible can be shared.
If QEMU *always* needed this setting, I could see adding it to the
init phase of seabios.  However, Windows doesn't seem to need it, and
it's unclear what VGA pass-through would require (though granted, that
has many other hurdles).

-Kevin