[SeaBIOS] [PATCH 2/2] accept MADT over fw_cfg

[Kevin O'Connor]

On Thu, Mar 21, 2013 at 03:26:26PM +0200, Michael S. Tsirkin wrote:
> On Thu, Mar 21, 2013 at 01:14:38PM +0000, David Woodhouse wrote:
> > On Thu, 2013-03-21 at 15:12 +0200, Michael S. Tsirkin wrote:
> > > Anyway, I am not against such runtime flags.
> > > 
> > > If we add to this an option to build a minimal BIOS
> > > that only works with the new QEMU, do we have a deal?
> > 
> > Yeah, definitely. The code for SeaBIOS to build its own should certainly
> > be optional. It should be possible to build a minimal SeaBIOS which
> > *can't*.

Agreed.

> Okay that's exactly what me and Laszlo are working on.
> We want to add a special way to build qemu and seabios
> such that they work with tables in qemu, then add
> runtime detection on top.
> 
> The advantage is that we can make progress
> without keeping lots of patches out of tree.
> Unless of course Kevin nacks this all ...

I think we need to have a plan for what the final interface will look
like.

Right now, we can't change QEMU to pass tables via the existing fw_cfg
entries unless we upgrade SeaBIOS in QEMU first (otherwise things like
duplicate MADT entries occur).  If we're going to upgrade SeaBIOS in
QEMU, we really want that upgrade to be the final version.  We don't
want to have to bump the seabios rev in qemu multiple times in
lock-step with the changes.

So, I see two ways to do this:

1 - update SeaBIOS with a patch series that makes it capable of
handling all tables via existing and new fw_cfg entries (including
flags to disable all internal tables), update QEMU to use that SeaBIOS
rev, and then apply a patch series to QEMU that has it create all the
tables (with the final patch flagging to seabios that it should no
longer create any internal tables).

or, 2 - apply a patch series to QEMU that has it create all the tables
via new fw_cfg entries, then apply a patch series to seabios that
updates it to use the new fw_cfg entries instead of its existing
internal tables, and then apply that new rev of seabios to qemu.

Were you proposing one of the above paths, or did you have something
else in mind?

-Kevin