Re: [Qemu-devel] [PATCH v3 2/2] vhost user: Add RARP injection for legacy guest

[Thibaut Collet <thibaut.collet@6wind.com>]

On Wed, Jun 17, 2015 at 8:42 AM, Michael S. Tsirkin <mst@redhat.com> wrote:
> On Wed, Jun 17, 2015 at 12:16:09PM +0800, Jason Wang wrote:
>>
>>
>> On 06/16/2015 04:16 PM, Thibaut Collet wrote:
>> > For a live migration my understanding is there are a suspend resume operation:
>> > - The VM image is regularly copied from the old host to the new one
>> > (modified pages due to VM operation can be copied several time)
>> > - As soon as there are only few pages to copy the VM is suspended on
>> > the old host, the last pages are copied, and the VM is resumed on the
>> > new host. Migration is not totally transparent  to guest that has a
>> > small period of unavailability.
>>
>> But guest is not involved in the any of the migration process. Unless
>> the performance drop, guest should not notice the migration at all.
>
> It is easy for backend to detect that guest started using the device,
> e.g. detect DRIVER_OK status set.
> I think that's enough to send RARPs.
>
>> Btw, please use bottom-posting which is easier for reader to understand
>> the context.
>>
>> Thanks
>
> I agree, please don't top-post.
>
> --
> MST

Sorry for top-posting rather than bottom-posting.

Regarding the use of DRIVER_OK, in your opinion, when is the best time
to test it ?