On Thu, Jul 6, 2023 at 10:02 PM Michael S. Tsirkin <[email protected]> wrote:
>
> On Thu, Jul 06, 2023 at 09:12:21PM +0200, Eugenio Pérez 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 RFC lift that requirement, sending the VHOST_VDPA_SET_VRING_ENABLE 
> > ioctl
> > for dataplane vqs only after the device has processed all commands.  If this
> > method is valid or not, or if it must be signalled by the parent driver
> > somehow, is still under discussion.  In case it is valid, this code allows
> > testing the vDPA device for it.
>
> And you plan to add the reset trick too in a future version?
>

I'll try to come with a version today.

At the current state of vDPA devices, it will just serve to enable
vp_vdpa to be the destination of a migration. But vp_vdpa cannot
migrate the guest again, so it is a dead end. I can try to add
_F_RING_RESET to vdpa_sim if that makes sense.

Anyway, as HW implement _F_RING_RESET, there should be no need to make
more changes to qemu, so we should be good.

> > Eugenio Pérez (6):
> >   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: remove net cvq migration blocker
> >
> >  include/hw/virtio/vhost-vdpa.h |  9 +++++++
> >  hw/virtio/vhost-vdpa.c         | 33 +++++++++++++++++++------
> >  net/vhost-vdpa.c               | 45 +++++++++++++++++++++++++---------
> >  hw/virtio/trace-events         |  2 +-
> >  4 files changed, 68 insertions(+), 21 deletions(-)
> >
> > --
> > 2.39.3
> >
>


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