Re: [libvirt] [Qemu-ppc] [RFC PATCH qemu] spapr_pci: Create PCI-express root bus by default

On Fri, 2016-12-02 at 15:18 +1100, David Gibson wrote: > But if you pass through multiple groups, things get weird.  On q35, > you'd generally expect physically separate (different slot) devices to > appear under separate root complexes.  Whereas on pseries they'll > appear as siblings on a virtual bus (which makes no physical sense for > point-to-point PCI-E). It's also somewhat broken if they aren't in the same iommu domain because the way we pass the iommu buid is via the parent node, so a given iommu domain must reside below a common parent and not share it.

> I suppose we could try treating all devices on pseries as though they > were chipset builtin devices on q35, which will appear on the root > PCI-E bus without root complex.  But I suspect that's likely to cause > trouble with hotplug, and it will certainly need different address > allocation from libvirt.