On Thu, Nov 13, 2014 at 05:43:14PM +0000, Daniel P. Berrange wrote: > On Thu, Nov 13, 2014 at 09:36:18AM -0800, Dan Smith wrote: > > > That sounds like something worth exploring at least, I didn't know > > > about that kernel build option until now :-) It sounds like it ought > > > to be enough to let us test the NUMA topology handling, CPU pinning > > > and probably huge pages too. > > > > Okay. I've been vaguely referring to this as a potential test vector, > > but only just now looked up the details. That's my bad :) > > > > > The main gap I'd see is NUMA aware PCI device assignment since the > > > PCI <-> NUMA node mapping data comes from the BIOS and it does not > > > look like this is fakeable as is. > > > > Yeah, although I'd expect that the data is parsed and returned by a > > library or utility that may be a hook for fakeification. However, it may > > very well be more trouble than it's worth. > > > > I still feel like we should be able to test generic PCI in a similar way > > (passing something like a USB controller through to the guest, etc). > > However, I'm willing to believe that the intersection of PCI and NUMA is > > a higher order complication :) > > Oh I forgot to mention with PCI device assignment (as well as having a > bunch of PCI devices available[1]), the key requirement is an IOMMU. > AFAIK, neither Xen or KVM provide any IOMMU emulation, so I think we're > out of luck for even basic PCI assignment testing inside VMs.
Ok, turns out that wasn't entirely accurate in general. KVM *can* emulate an IOMMU, but it requires that the guest be booted with the q35 machine type, instead of the ancient PIIX4 machine type, and also QEMU must be launched with "-machine iommu=on". We can't do this in Nova, so although it is theoretically possible, it is not doable for us in reality :-( Regards, Daniel -- |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| |: http://libvirt.org -o- http://virt-manager.org :| |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| _______________________________________________ OpenStack-dev mailing list [email protected] http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
