Re: [Qemu-devel] [RFC 3/3] acpi-build: allocate mcfg for multiple host bridges

[Marcel Apfelbaum]

On 05/23/2018 10:32 AM, Laszlo Ersek wrote:
> On 05/23/18 01:40, Michael S. Tsirkin wrote:
> > On Wed, May 23, 2018 at 12:42:09AM +0200, Laszlo Ersek wrote:
> > > Hold on,
> > >
> > > On 05/22/18 21:51, Laszlo Ersek wrote:
> > >
> > > > It had taken years until the edk2 core gained a universal
> > > > PciHostBridgeDxe driver with a well-defined platform customization
> > > > interface, and that interface doesn't support multiple domains /
> > > > segments.
> > > after doing a bit more research: I was wrong about this. What I
> > > remembered was not the current state. Edk2 does seem to support multiple
> > > domains, with different segment numbers, ECAM base addresses, and bus
> > > number ranges.

Good news!

> > >   If we figure out a placement strategy or an easy to
> > > consume representation of these data for the firmware, it might be
> > > possible for OVMF to hook them into the edk2 core (although not in the
> > > earliest firmware phases, such as SEC and PEI).

Can you please remind me how OVMF places the 64-bit PCI hotplug window?
We may do something similar.
Let me emphasize,  I am not implying you/anybody else should work on 
that :),
I just want to be on the same page if/when the time will come.
For the moment we are looking for a POC, nothing more.

> > > In retrospect, I'm honestly surprised that so much multi-segment support
> > > has been upstreamed to the edk2 core. Sorry about the FUD. (My general
> > > points remain valid, for the record... But perhaps they no longer matter
> > > for this discussion.)
> > >
> > > (I meant to send this message soon after
> > > <http://mid.mail-archive.com/address@hidden>,
> > > but my internet connection had to die right then.)
> > >
> > > Thanks
> > > Laszlo
> > Is there support for any hardware which we could emulate?
> I don't see any actual hw support in the edk2 project, but I'll ask.

I think we may be able to succeed with "standard" APCI declarations of
the PCI segments + placing the extra MMCONFIG ranges before the 64-bit 
PCI hotplug area.

Thanks,
Marcel

> Thanks
> Laszlo