[Qemu-devel] [0/2] pseries: Rework PCI code for handling multiple PHBs

[David Gibson]

Hi Michael, Alex,

This patch represents a compromise I hope will be acceptable after the
long thread discussing handling of multiple PCI host bridges on the
pseries machine.  Patch 1/1 is just a preliminary enforcing uniqueness
of LIOBNs in the IOMMU code.

Patch 2/2 is the meat.  It allows either explicit configuration of all
the properties, or the user can just set an abstract index which will
generate sensible and probably-unique values for all the rest.

With these patches I was able to do something like:
        qemu-system-ppc64 -M pseries -m 1024 -nographic \
        fc17-root.qcow2 -net none -device nec-usb-xhci -device \
        spapr-pci-host-bridge,index=1 -device e1000,netdev=fred \
        -netdev user,id=fred

I was able to see both the PCI domains in the guest, and use the NIC
on the secondary domain.

There are still some gotches with multiple domains though.  The domain
value in PCIHostBus is still always initialized to 0, and there are
other places in the PCI core where handling of multiple domains is
essentially stubbed out.

Michael, any thoughts on what to do about that?  I could fix up the
PCI code so that domain is actually set and used.  But I think the
whole notion of domain numbers is kind of bogus on the qemu side:
since PCI domains are completely independent from each other, it's
only platform convention which determines what the domain numbers are.
On platforms that don't have a strong convention, the guest will
number them itself and we have no way of knowing that.  So it seems to
me that the PCI code should instead of domain numbers just use the
device ID, or the bus name or some qemu side symbolic name.  For
platforms that do have a numbering convention those names can be
derived from the domain numbers, but it also works for platforms that
don't.