Open Stack

On Tue, Nov 25, 2014 at 2:01 PM, Steve Gordon <sgordon at redhat.com> wrote:

> ----- Original Message -----
> > From: "Daniel P. Berrange" <berrange at redhat.com>
> > To: "Dan Smith" <dms at danplanet.com>
> >
> > 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
>
> Is it worth still pursuing virtual testing of the NUMA awareness work you,
> nikola, and others have been doing? It seems to me it would still be
> preferable to do this virtually (and ideally in the gate) wherever possible?
>

The more we can test in the gate and without real hardware the better.


>
> Thanks,
>
> Steve
>
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