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Please see inline

On Thu, Feb 19, 2015 at 4:43 PM, Steve Gordon <sgordon at redhat.com> wrote:

> ----- Original Message -----
> > From: "Irena Berezovsky" <irenab.dev at gmail.com>
> > To: "OpenStack Development Mailing List (not for usage questions)" <
> openstack-dev at lists.openstack.org>,
> >
> > On Thu, Feb 5, 2015 at 9:01 PM, Steve Gordon <sgordon at redhat.com> wrote:
> >
> > > ----- Original Message -----
> > > > From: "Przemyslaw Czesnowicz" <przemyslaw.czesnowicz at intel.com>
> > > > To: "OpenStack Development Mailing List (not for usage questions)" <
> > > openstack-dev at lists.openstack.org>
> > > >
> > > > Hi
> > > >
> > > > > 1) If the device is a "normal" PCI device, but is a network card,
> am I
> > > > > still able to
> > > > > take advantage of the advanced syntax added circa Juno to define
> the
> > > > > relationship between that card and a given physical network so
> that the
> > > > > scheduler can place accordingly (and does this still use the ML2
> mech
> > > > > drvier for
> > > > > SR-IOV even though it's a "normal" device.
> > > >
> > > > Actually libvirt won't allow using "normal" PCI devices for network
> > > > interfaces into VM.
> > > > Following error is thrown by libvirt 1.2.9.1:
> > > > libvirtError: unsupported configuration: Interface type hostdev is
> > > currently
> > > > supported on SR-IOV Virtual Functions only
> > > >
> > > > I don't know why libvirt prohibits that. But we should prohibit that
> on
> > > > Openstack side as well.
> > >
> > > This is true for hostdev"> style configuration, "normal" PCI devices
> are
> > > still valid in Libvirt for passthrough using <hostdev> though. The
> former
> > > having been specifically created for handling passthrough of VFs, the
> > > latter being the more generic passthrough functionality and what was
> used
> > > with the original PCI passthrough functionality introduced circa
> Havana.
> > >
> > > I guess what I'm really asking in this particular question is what is
> the
> > > intersection of these two implementations - if any, as on face value it
> > > seems that to passthrough a physical PCI device I must use the older
> syntax
> > > and thus can't have the scheduler be aware of its external network
> > > connectivity.
> > >
> > Support for "normal" PCI device passthrough for networking in SR-IOV like
> > way will require new VIF Driver support for hostdev style device guest
> XML
> > being created and some call invocation to set MAC address and VLAN tag.
> >
> > >
> > > > > 2) There is no functional reason from a Libvirt/Qemu perspective
> that I
> > > > > couldn't
> > > > > pass through a PF to a guest, and some users have expressed
> surprise
> > > to me
> > > > > when they have run into this check in the Nova driver. I assume in
> the
> > > > > initial
> > > > > implementation this was prevented to avoid a whole heap of fun
> > > additional
> > > > > logic
> > > > > that is required if this is allowed (e.g. check that no VFs from
> the PF
> > > > > being
> > > > > requested are already in use, remove all the associated VFs from
> the
> > > pool
> > > > > when
> > > > > assigning the PF, who gets allowed to use PFs versus VFs etc.). Am
> I
> > > > > correct here
> > > > > or is there another reason that this would be undesirable to allow
> in
> > > > > future -
> > > > > assuming such checks can also be designed - that I am missing?
> > > > >
> > > > I think that is correct. But even if the additional logic was
> > > implemented  it
> > > > wouldn't work because of how libvirt behaves currently.
> > >
> > > Again though, in the code we have a distinction between a physical
> device
> > > (as I was asking about in Q1) and a physical function (as I am asking
> about
> > > in Q2) and similarly whether libvirt allows or not depends on how you
> > > configure in the guest XML. Though I wouldn't be surprised on the PF
> case
> > > if it is in fact not allowed in Libvirt (even with <hostdev>) it is
> again
> > > important to consider this distinctly separate from passing through the
> > > physical device case which we DO allow currently in the code I'm asking
> > > about.
> > >
> > I think what you suggest is not difficult to support, but current (since
> > Juno) PCI device passthrough  for networking is all about SR-IOV PCI
> device
> > passthrough. As I mentioned, to support  "normal" PCI device will require
> > libvirt VIF Driver adjustment. I think its possible to make this work
> with
> > existing neutron ML2 SRIOV Mechanism Driver.
>
> Understood, was just trying to understand if there was an explicit reason
> *not* to do this. How should we track this, keep adding to
> https://etherpad.openstack.org/p/kilo_sriov_pci_passthrough ?
>

I think that probably new etherpad for Liberty should be  created in order
to track SR-IOV and PCI features. Most of the features proposed for Kilo
were rejected due to the nova and neutron priorities focus on other areas.
All listed and rejected features and new features priorities should be
evaluated and probably picked by people willing to drive it. For Kilo we
started this work during the pci_passthrough weekly meetings and finalized
at the summit. I think it worked well. I would suggest to do the same for
Liberty.

BR,
Irena


> Thanks,
>
> Steve
>
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