Re: [PATCH v2 3/3] vdpa/mlx5: defer clear_virtqueues to until DRIVER_OK

[Jason Wang]

On 2021/2/18 上午5:55, Si-Wei Liu wrote:
> On 2/16/2021 7:21 AM, Eli Cohen wrote:
> > On Thu, Feb 11, 2021 at 09:33:14AM +0200, Eli Cohen wrote:
> > > On Wed, Feb 10, 2021 at 01:48:00PM -0800, Si-Wei Liu wrote:
> > > > While virtq is stopped,  get_vq_state() is supposed to
> > > > be  called to  get  sync'ed  with  the latest internal
> > > > avail_index from device. The saved avail_index is used
> > > > to restate  the virtq  once device is started.  Commit
> > > > b35ccebe3ef7 introduced the clear_virtqueues() routine
> > > > to  reset  the saved  avail_index,  however, the index
> > > > gets cleared a bit earlier before get_vq_state() tries
> > > > to read it. This would cause consistency problems when
> > > > virtq is restarted, e.g. through a series of link down
> > > > and link up events. We  could  defer  the  clearing of
> > > > avail_index  to  until  the  device  is to be started,
> > > > i.e. until  VIRTIO_CONFIG_S_DRIVER_OK  is set again in
> > > > set_status().
> > > >
> > > > Fixes: b35ccebe3ef7 ("vdpa/mlx5: Restore the hardware used index 
> > > > after change map")
> > > > Signed-off-by: Si-Wei Liu <si-wei.liu@xxxxxxxxxx>
> > > > Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
> > > Acked-by: Eli Cohen <elic@xxxxxxxxxx>
> > I take it back. I think we don't need to clear the indexes at all. In
> > case we need to restore indexes we'll get the right values through
> > set_vq_state(). If we suspend the virtqueue due to VM being suspended,
> > qemu will query first and will provide the the queried value. In case of
> > VM reboot, it will provide 0 in set_vq_state().
> >
> > I am sending a patch that addresses both reboot and suspend.
> With set_vq_state() repurposed to restoring used_index I'm fine with 
> this approach.
>
> Do I have to repost a v3 of this series while dropping the 3rd patch?
>
> -Siwei 


Yes, please.

Thanks