On 05/22/18 23:47, Alex Williamson wrote: > On Wed, 23 May 2018 00:44:22 +0300 > "Michael S. Tsirkin" <m...@redhat.com> wrote: > >> On Tue, May 22, 2018 at 03:36:59PM -0600, Alex Williamson wrote: >>> 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. >> >> What are you calling a PCIe domain? > > Domain/segment > > 0000:00:00.0 > ^^^^ This > > Isn't that the only reason we'd need a new MCFG section and the reason > we're limited to 256 buses? Thanks,
(Just to confirm: this matches my understanding of the thread as well.) Laszlo
