On Sun, Dec 06, 2020 at 12:57:19PM +0200, Eli Cohen wrote:
> Make sure to put write memory barrier after updating CQ consumer index
> so the hardware knows that there are available CQE slots in the queue.
>
> Failure to do this can cause the update of the RX doorbell record to get
> updated before the CQ consumer index resulting in CQ overrun.
>
> Change-Id: Ib0ae4c118cce524c9f492b32569179f3c1f04cc1
> Fixes: 1a86b377aa21 ("vdpa/mlx5: Add VDPA driver for supported mlx5 devices")
> Signed-off-by: Eli Cohen <e...@nvidia.com>
Aren't both memory writes? And given that, isn't dma_wmb() sufficient
here?
> ---
> drivers/vdpa/mlx5/net/mlx5_vnet.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index 1f4089c6f9d7..295f46eea2a5 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -478,6 +478,11 @@ static int mlx5_vdpa_poll_one(struct mlx5_vdpa_cq *vcq)
> static void mlx5_vdpa_handle_completions(struct mlx5_vdpa_virtqueue *mvq,
> int num)
> {
> mlx5_cq_set_ci(&mvq->cq.mcq);
> +
> + /* make sure CQ cosumer update is visible to the hardware before
> updating
> + * RX doorbell record.
> + */
> + wmb();
> rx_post(&mvq->vqqp, num);
> if (mvq->event_cb.callback)
> mvq->event_cb.callback(mvq->event_cb.private);
> --
> 2.27.0
