[Qemu-ppc] PCI Express on pseries guests

[Andrea Bolognani]

I was wondering whether it's possible to create a pseries guest
that uses PCI Express instead of legacy PCI.

The host itself is using PCI Express only

  $ sudo lspci -vv | grep -Ec '^[0-9]'
  28
  $ sudo lspci -vv | grep -Ec '^.*Capabilities: \[..\] Express'
  28

but pseries guests seem to use legacy PCI instead

  $ echo -e "info qtree\nquit" \
    | ./ppc64-softmmu/qemu-system-ppc64 \
      -nodefaults -nographic -no-user-config \
      -M pseries,accel=kvm \
      -cpu host \
      -monitor stdio \
    | grep \
      -i pci
  dev: spapr-pci-host-bridge, id ""
      bus: pci.0
            type PCI

AFAIU, the spapr-pci-host-bridge is connected to the
main-system-bus and that creates a legacy PCI bridge that
PCI devices can be attached to.

The corresponding spapr-pcie-host-bridge device doesn't seem
to exist; pxb-pcie looks promising, but if I try using it
QEMU rightfully complains

  pxb-pcie devices cannot reside on a PCI bus!

So at this point I'm pretty much stuck. Suggestions? :)

-- 
Andrea Bolognani / Red Hat / Virtualization