[SeaBIOS] [PATCH] Don't overallocate mptable

[Gleb Natapov]

On Thu, Dec 24, 2009 at 12:22:12PM -0500, Kevin O'Connor wrote:
> On Thu, Dec 24, 2009 at 06:54:55PM +0200, Gleb Natapov wrote:
> > On Thu, Dec 24, 2009 at 11:38:45AM -0500, Kevin O'Connor wrote:
> > >      foreachpci(bdf, max) {
> > > +        if (pci_bdf_to_bus(bdf) > 0)
> > > +            break;
> > mptable routing info should be created for each pci bus.
> 
> My read of the spec is that independent PCI buses need to be added to
> the MPTable, but a bus created due to a PCI-to-PCI bridge (eg, on an
> add-on card) need not go into the table.
> 
> > See example here:
Ah so pci_bdf_to_bus(bdf) > 0 for the bus behind PCI-to-PCI bridge?
I don't wee why you read spec this way. Can you point me to the part of
the spec that makes you think so?

> > http://people.freebsd.org/~fsmp/SMP/mptable/t30
> 
> In that example, it looks like the machine has two independent buses -
> note how bus 1 has more than four irqs - so it can't be an add-on
> card.
Yes. In this example there are several PCI domains.

> 
> > Hmm. It looks like we need to create io_bus entries dynamically 
> > for each newly discovered PCI bus.
> 
> Right now, the pciinit.c code handles neither PCI-to-PCI bridges nor
> independent PCI bridges.  I think it would be useful to support
> bridges (for mapping in add-on cards that have them), but I don't know
> why an emulator would want to have independent buses.  Note that it's
> difficult to detect an independent bus - some sideband mechanism is
> needed (eg, see CONFIG_PCI_ROOT1 in src/config.h).
> 

--
			Gleb.