On Sat, Feb 06, 2021 at 04:29:24AM -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().
Not sure I understand the scenario. You are talking about reset of the
device followed by up/down events on the interface. How can you trigger
this?
>
> Fixes: b35ccebe3ef7 ("vdpa/mlx5: Restore the hardware used index after change
> map")
> Signed-off-by: Si-Wei Liu <si-wei....@oracle.com>
> ---
> 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 aa6f8cd..444ab58 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -1785,7 +1785,6 @@ 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;
> @@ -1794,6 +1793,7 @@ 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
>
