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....@oracle.com>
> > Acked-by: Jason Wang <jasow...@redhat.com>
>
> Acked-by: Eli Cohen <e...@nvidia.com>
>
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.
> > ---
> > drivers/vdpa/mlx5/net/mlx5_vnet.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > index 7c1f789..ce6aae8 100644
> > --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> > @@ -1777,7 +1777,6 @@ static void mlx5_vdpa_set_status(struct vdpa_device
> > *vdev, u8 status)
> > if (!status) {
> > mlx5_vdpa_info(mvdev, "performing device reset\n");
> > teardown_driver(ndev);
> > - clear_virtqueues(ndev);
> > mlx5_vdpa_destroy_mr(&ndev->mvdev);
> > ndev->mvdev.status = 0;
> > ++mvdev->generation;
> > @@ -1786,6 +1785,7 @@ static void mlx5_vdpa_set_status(struct vdpa_device
> > *vdev, u8 status)
> >
> > if ((status ^ ndev->mvdev.status) & VIRTIO_CONFIG_S_DRIVER_OK) {
> > if (status & VIRTIO_CONFIG_S_DRIVER_OK) {
> > + clear_virtqueues(ndev);
> > err = setup_driver(ndev);
> > if (err) {
> > mlx5_vdpa_warn(mvdev, "failed to setup
> > driver\n");
> > --
> > 1.8.3.1
> >
