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

On 2021/2/18 上午5:55, Si-Wei Liu wrote:

On 2/16/2021 7:21 AM, Eli Cohen wrote:

quoted

On Thu, Feb 11, 2021 at 09:33:14AM +0200, Eli Cohen wrote:

quoted

On Wed, Feb 10, 2021 at 01:48:00PM -0800, Si-Wei Liu wrote:

quoted

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 <redacted>
Acked-by: Jason Wang <redacted>

Acked-by: Eli Cohen <redacted>

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