[SeaBIOS] [PATCH] optionrom: disallow int19 redirect for pnp roms.

[Gerd Hoffmann]

On Tue, Nov 27, 2018 at 09:19:09PM -0500, Kevin O'Connor wrote:
> On Tue, Nov 27, 2018 at 01:10:38PM +0100, Gerd Hoffmann wrote:
> > Check whenever pnp roms attempt to redirect int19, and in case it does
> > log a message and undo the redirect.
> > 
> > A pnp rom should not need this, we have BEVs and BCVs for that.
> > Nevertheless there are roms in the wild which are redirecting int19.
> > At least some BIOS implementations for physical hardware have a config
> > option in the setup to allow/disallow int19 redirections, so just not
> > allowing this seems to be the way to deal with this situation.
> > 
> > Buglink: https://bugzilla.redhat.com//show_bug.cgi?id=1642135
> 
> That is very odd.  I'm pretty sure iPXE normally does register itself
> as a BEV - any idea why it's now hooking int19?

It's not ipxe.

It is the rom of a intel nic, attached to a guest via pci passthrough.
It does both, register bev and hook int19.  No clue why.  The only
reason I can think of is backward compatibility to firmware so old that
it doesn't know pnp roms.  Which is a silly thing in pci express
hardware.  Maybe they carry forward that code since decades ...

> I'm leery of making a change like this, because there's a good chance
> it will break something in some other obscure software.

I've added a rather verbose message printing some information about the
rom because of that.

> I think fixing this in iPXE would be preferable if possible.

See above. ipxe doesn't need fixing.

cheers,
  Gerd