Re: [PATCH net-next 5/5] net/mlx5e: do not create xdp_redirect for non-uplink rep

[Daniel Machon <daniel.machon@microchip.com>]

Hi Tariq, William

> From: William Tu <witu@nvidia.com>
> 
> XDP and XDP socket require extra SQ/RQ/CQs. Most of these resources
> are dynamically created: no XDP program loaded, no resources are
> created. One exception is the SQ/CQ created for XDP_REDRIECT, used
> for other netdev to forward packet to mlx5 for transmit. The patch
> disables creation of SQ and CQ used for egress XDP_REDIRECT, by
> checking whether ndo_xdp_xmit is set or not.
> 
> For netdev without XDP support such as non-uplink representor, this
> saves around 0.35MB of memory, per representor netdevice per channel.
> 
> Signed-off-by: William Tu <witu@nvidia.com>
> Reviewed-by: Parav Pandit <parav@nvidia.com>
> Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
> ---
>  .../net/ethernet/mellanox/mlx5/core/en_main.c   | 17 +++++++++++------
>  1 file changed, 11 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> index 2f609b92d29b..59d7a0e28f24 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> @@ -2514,6 +2514,7 @@ static int mlx5e_open_queues(struct mlx5e_channel *c,
>                              struct mlx5e_params *params,
>                              struct mlx5e_channel_param *cparam)
>  {
> +       const struct net_device_ops *netdev_ops = c->netdev->netdev_ops;
>         struct dim_cq_moder icocq_moder = {0, 0};
>         struct mlx5e_create_cq_param ccp;
>         int err;
> @@ -2534,10 +2535,12 @@ static int mlx5e_open_queues(struct mlx5e_channel *c,
>         if (err)
>                 goto err_close_icosq_cq;
> 
> -       c->xdpsq = mlx5e_open_xdpredirect_sq(c, params, cparam, &ccp);
> -       if (IS_ERR(c->xdpsq)) {
> -               err = PTR_ERR(c->xdpsq);
> -               goto err_close_tx_cqs;
> +       if (netdev_ops->ndo_xdp_xmit) {

Is it possible to have ndo_xdp_xmit() set, but *not* have an XDP prog attached
to the netdevice? I see that c->xdp = !!params->xdp_prog - could that be
used instead?

/Daniel

> +               c->xdpsq = mlx5e_open_xdpredirect_sq(c, params, cparam, &ccp);
> +               if (IS_ERR(c->xdpsq)) {
> +                       err = PTR_ERR(c->xdpsq);
> +                       goto err_close_tx_cqs;
> +               }
>         }
> 
>         err = mlx5e_open_cq(c->mdev, params->rx_cq_moderation, &cparam->rq.cqp, &ccp,
> @@ -2601,7 +2604,8 @@ static int mlx5e_open_queues(struct mlx5e_channel *c,
>         mlx5e_close_cq(&c->rq.cq);
> 
>  err_close_xdpredirect_sq:
> -       mlx5e_close_xdpredirect_sq(c->xdpsq);
> +       if (c->xdpsq)
> +               mlx5e_close_xdpredirect_sq(c->xdpsq);
> 
>  err_close_tx_cqs:
>         mlx5e_close_tx_cqs(c);
> @@ -2629,7 +2633,8 @@ static void mlx5e_close_queues(struct mlx5e_channel *c)
>         if (c->xdp)
>                 mlx5e_close_cq(&c->rq_xdpsq.cq);
>         mlx5e_close_cq(&c->rq.cq);
> -       mlx5e_close_xdpredirect_sq(c->xdpsq);
> +       if (c->xdpsq)
> +               mlx5e_close_xdpredirect_sq(c->xdpsq);
>         mlx5e_close_tx_cqs(c);
>         mlx5e_close_cq(&c->icosq.cq);
>         mlx5e_close_cq(&c->async_icosq.cq);
> --
> 2.44.0
> 
>