[SeaBIOS] [RFC v3] pciinit: setup mcfg for pxb-pcie to support multiple pci domains

[Kevin O'Connor]

On Thu, Sep 27, 2018 at 11:05:13PM +0800, Zihan Yang wrote:
> Laszlo Ersek <lersek at redhat.com> 于2018年9月26日周三 上午1:17写道：
> > First, I fail to see the use case where ~256 PCI bus numbers aren't
> > enough. If I strain myself, perhaps I can imagine using ~200 PCIe root
> > ports on Q35 (each of which requires a separate bus number), so that we
> > can independently hot-plug 200 devices then. And that's supposedly not
> > enough, because we want... 300? 400? A thousand? Doesn't sound realistic
> > to me. (This is not meant to be a strawman argument, I really have no
> > idea what the feature would be useful for.)
> 
> It might not be very intuitive, but it indeed exists. The very
> beginning discussion
> about 4 months ago has mentioned a possible use case, and I paste it here
[...]
> Things might change in the future if we can figure out a better solution, and I
> hope we can have an easier and more elegant solution in OVMF. But now
> we are just trying to give a possible solution as a poc.

Thanks.  I wasn't aware this was a proof of concept.  (Nor have I been
following the discussions on the qemu list.)  I don't think it makes
sense to merge this into the main SeaBIOS repository.  The
QEMU/firmware interface is already complex and I don't think we should
complicate it further without a more concrete use case.  In
particular, it seems unclear if 256 buses is enough or if 1024 buses
is too little.

-Kevin