On Tue, 22 May 2018 23:58:30 +0300 "Michael S. Tsirkin" <m...@redhat.com> wrote: > > It's not hard to think of a use-case where >256 devices > are helpful, for example a nested virt scenario where > each device is passed on to a different nested guest. > > But I think the main feature this is needed for is numa modeling. > Guests seem to assume a numa node per PCI root, ergo we need more PCI > roots.
But even if we have NUMA affinity per PCI host bridge, a PCI host bridge does not necessarily imply a new PCIe domain. Nearly any Intel multi-socket system proves this. Don't get me wrong, I'd like to see PCIe domain support and I'm surprised edk2 is so far from supporting it, but other than >256 hotpluggable slots, I'm having trouble coming up with use cases. Maybe hotpluggable PCI root hierarchies are easier with separate domains? Thanks, Alex