Open Stack

In general, while you've applied this to networking (and it's not the first
time I've seen this proposal), the same technique will work with any device
- PF or VF, networking or other:

- notify the VM via an accepted channel that a device is going to be
temporarily removed
- remove the device
- migrate the VM
- notify the VM that the device is going to be returned
- reattach the device

Note that, in the above, I've not used said 'PF', 'VF', 'NIC' or 'qemu'.

You would need to document what assumptions the guest is going to make (the
reason I mention this is I think it's safe to assume the device has been
recently reset here, but for a network device you might want to consider
whether the device will have the same MAC address or number of tx and rx
buffers, for instance).

The method of notification I've deliberately skipped here; you have an
answer for qemu, qemu is not the only hypervisor in the world so this will
clearly be variable.  A metadata server mechanism is another possibility.

Half of what you've described is one model of how the VM might choose to
deal with that (and a suggestion that's come up before, in fact) - that's a
model we would absolutely want Openstack to support (and I think the above
is sufficient to support it), but we can't easily mandate how VMs behave,
so from the Openstack perspective it's more a recommendation than anything
we can code up.


On 15 February 2016 at 23:25, Xie, Xianshan <xiexs at cn.fujitsu.com> wrote:

> Hi, Fawad,
>
>
>
>
>
> > Can you please share the link?
>
>
> https://blueprints.launchpad.net/nova/+spec/direct-pci-passthrough-live-migration
>
>
>
> Thanks in advance.
>
>
>
>
>
> Best regards,
>
> xiexs
>
>
>
> *From:* Fawad Khaliq [mailto:fawad at plumgrid.com]
> *Sent:* Tuesday, February 16, 2016 1:19 PM
> *To:* OpenStack Development Mailing List (not for usage questions)
> *Subject:* Re: [openstack-dev] [nova][neutron] New BP for live migration
> with direct pci passthru
>
>
>
> On Mon, Feb 1, 2016 at 3:25 PM, Xie, Xianshan <xiexs at cn.fujitsu.com>
> wrote:
>
> Hi, all,
>   I have registered a new BP about the live migration with a direct pci
> passthru device.
>   Could you please help me to review it? Thanks in advance.
>
>
>
> Can you please share the link?
>
>
>
>
> The following is the details:
>
> ----------------------------------------------------------------------------------
> SR-IOV has been supported for a long while, in the community's point of
> view,
> the pci passthru with Macvtap can be live migrated possibly, but the
> direct pci passthru
> seems hard to implement the migration as the passthru VF is totally
> controlled by
> the VMs so that some internal states may be unknown by the hypervisor.
>
> But we think the direct pci passthru model can also be live migrated with
> the
> following combination of a series of technology/operation based on the
> enhanced
> Qemu-Geust-Agent(QGA) which has already been supported by nova.
>    1)Bond the direct pci passthru NIC with a virtual NIC.
>      This will keep the network connectivity during the live migration.
>    2)Unenslave the direct pci passthru NIC
>    3)Hot-unplug the direct pci passthru NIC
>    4)Live-migrate guest with the virtual NIC
>    5)Hot-plug the direct pci passthru NIC on the target host
>    6)Enslave the direct pci passthru NIC
>
> And more inforation about this concept can refer to [1].
> [1]https://www.kernel.org/doc/ols/2008/ols2008v2-pages-261-267.pdf
>
> ----------------------------------------------------------------------------------
>
> Best regards,
> Xiexs
>
>
>
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