Need some explanation on SRIOV with MAAS/juju/charm

[James Page]

Hi Guillaume

On Mon, 19 Jun 2017 at 13:44 Guillaume Harvey <
guillaume.harvey at canonical.com> wrote:

> hello folks!
>
> I have question about SRIOV in juju. What tell juju which node have SRIOV
> enable to be able to boot instance using . -nic port-id=<port-uuid>?
>
> My client have two cloud, one with juju (poc) and one another with OSA
> (preprod). They want to try to enable the SRIOV funtionality on their
> preprod, but it says no host available. I tried to check and juju dont
> create host aggregate and not even put some metadata on flavor.
>
> How is it done? Is it done in MAAS or juju or charms?
>

Pretty much all of those; let me add some detail:

1) MAAS - in order to use SR-IOV devices, you must boot servers with
specific kernel boot options - which ones exactly will depend on your
hardware:

http://www.linux-kvm.org/page/How_to_assign_devices_with_VT-d_in_KVM

The best way to set this is using a maas tag, to which you can attach the
correct kernel command line options;  You'll probably also want to add
hugepage configuration here as well.  The nova-compute charm can *try* to
configure hugepages post boot, but that's not guaranteed due to other OS
processes starting to consume memory after initial kernel boot.  Ditto on
CPU isolation if that's something else you want to use.

2)  Charms

The nova-compute [1]  and neutron-openvswitch charms both have
configuration options related to PCI device management for SR-IOV; these
feature basically ensure that the SR-IOV cards are configured for VF usage,
and slurps them into the nova database for PCI device allocation purposes.
There is also a review in flight which will make it much easier to
associate a SR-IOV VF device type with a nova flavor (see [3]).

[1] https://jujucharms.com/nova-compute/
[2] https://jujucharms.com/neutron-openvswitch/#charm-config-enable-sriov
[3] https://review.openstack.org/#/c/434708/

3) Juju

Once we have the last part of 2) landed (the pci-alias work), you will be
able to grab SR-IOV enabled instances by configuring some flavors on the
cloud with the charm configured pci aliases, which you can then access from
Juju using instance-type constraints.  We should have those bits landed
soon!  I think this is the piece of the puzzle you are probably missing at
the moment.

Hope that helps explain things a bit.

Cheers

James
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