Re: [PATCH 1/2] virtio: introduce selective queue enabling

[Eugenio Perez Martin <eperezma@redhat.com>]

On Tue, Jun 13, 2023 at 9:50âAM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> On Tue, Jun 06, 2023 at 07:55:10PM +0200, Eugenio PÃrez wrote:
> > This patch allows the driver to start the device (as set DRIVER_OK) with only
> > some queues enabled, and then enable another queues later.
> >
> > This is the current way to migrate net device state through control
> > virtqueue, in a software assisted framework with vDPA:
> > * First, only net CVQ is enabled at DRIVER_OK
> > * All the control commands (mac address, mq, etc) needed for the device
> > to behave the same as the source of migration are sent
> > * Finally all the dataplane queues are enabled.
> >
> > Signed-off-by: Eugenio PÃrez <eperezma@redhat.com>
>
>
> I realized I never asked. *Why* enable CVQ so early?
> I think it's so that commands take effect before any
> buffers are processed? So maybe it's a net specific
> issue?
>

Yes, that's the reason. Can I add something to the patch message to
make it clearer?

It can be solved using a net specific solution for sure, but I think
we can make it general if other devices with CVQ have such needs.

Thanks.