On Mon, Jul 31, 2023 at 8:41 AM Jason Wang <jasow...@redhat.com> wrote:
>
> On Sat, Jul 29, 2023 at 1:20 AM Eugenio Pérez <epere...@redhat.com> wrote:
> >
> > At this moment the migration of net features that depends on CVQ is not
> > possible, as there is no reliable way to restore the device state like mac
> > address, number of enabled queues, etc to the destination. This is mainly
> > caused because the device must only read CVQ, and process all the commands
> > before resuming the dataplane.
> >
> > This series lift that requirement, sending the VHOST_VDPA_SET_VRING_ENABLE
> > ioctl for dataplane vqs only after the device has processed all commands.
>
> I think it's better to explain (that is what I don't understand) why
> we can not simply reorder vhost_net_start_one() in vhost_net_start()?
>
> for (i = 0; i < nvhosts; i++) {
> if (i < data_queue_pairs) {
> peer = qemu_get_peer(ncs, i);
> } else {
> peer = qemu_get_peer(ncs, n->max_queue_pairs);
> }
>
> if (peer->vring_enable) {
> /* restore vring enable state */
> r = vhost_set_vring_enable(peer, peer->vring_enable);
>
> if (r < 0) {
> goto err_start;
> }
> }
>
> => r = vhost_net_start_one(get_vhost_net(peer), dev);
> if (r < 0) {
> goto err_start;
> }
> }
>
> Can we simply start cvq first here?
>
Well the current order is:
* set dev features (conditioned by
* Configure all vq addresses
* Configure all vq size
...
* Enable cvq
* DRIVER_OK
* Enable all the rest of the queues.
If we just start CVQ first, we need to modify vhost_vdpa_set_features
as minimum. A lot of code that depends on vdev->vq_index{,_end} may be
affected.
Also, I'm not sure if all the devices will support configure address,
vq size, etc after DRIVER_OK.
> Thanks
>
> > ---
> > From FRC:
> > * Enable vqs early in case CVQ cannot be shadowed.
> >
> > Eugenio Pérez (7):
> > vdpa: export vhost_vdpa_set_vring_ready
> > vdpa: add should_enable op
> > vdpa: use virtio_ops->should_enable at vhost_vdpa_set_vrings_ready
> > vdpa: add stub vhost_vdpa_should_enable
> > vdpa: delay enable of data vqs
> > vdpa: enable cvq svq if data vq are shadowed
> > vdpa: remove net cvq migration blocker
> >
> > include/hw/virtio/vhost-vdpa.h | 9 +++++
> > hw/virtio/vhost-vdpa.c | 33 ++++++++++++----
> > net/vhost-vdpa.c | 69 ++++++++++++++++++++++++++--------
> > hw/virtio/trace-events | 2 +-
> > 4 files changed, 89 insertions(+), 24 deletions(-)
> >
> > --
> > 2.39.3
> >
> >
>
