linux-kernel - Re: [PATCH net-next] eth: mlx5: link NAPI instances to queues and IRQs

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Message-ID: <878r3ymlnk.fsf@nvidia.com>
Date: Mon, 05 Feb 2024 17:09:09 -0800
From: Rahul Rameshbabu <rrameshbabu@...dia.com>
To: Joe Damato <jdamato@...tly.com>
Cc: linux-kernel@...r.kernel.org, netdev@...r.kernel.org, tariqt@...dia.com,
 Saeed Mahameed <saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
 <pabeni@...hat.com>, "open list:MELLANOX MLX5 core VPI driver"
 <linux-rdma@...r.kernel.org>
Subject: Re: [PATCH net-next] eth: mlx5: link NAPI instances to queues and IRQs

On Tue, 06 Feb, 2024 01:03:11 +0000 Joe Damato <jdamato@...tly.com> wrote:
> Make mlx5 compatible with the newly added netlink queue GET APIs.
>
> Signed-off-by: Joe Damato <jdamato@...tly.com>
> ---
>  drivers/net/ethernet/mellanox/mlx5/core/en.h      | 1 +
>  drivers/net/ethernet/mellanox/mlx5/core/en_main.c | 8 ++++++++
>  2 files changed, 9 insertions(+)
>
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en.h b/drivers/net/ethernet/mellanox/mlx5/core/en.h
> index 55c6ace0acd5..3f86ee1831a8 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en.h
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en.h
> @@ -768,6 +768,7 @@ struct mlx5e_channel {
>  	u16                        qos_sqs_size;
>  	u8                         num_tc;
>  	u8                         lag_port;
> +	unsigned int		   irq;
>  
>  	/* XDP_REDIRECT */
>  	struct mlx5e_xdpsq         xdpsq;
> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> index c8e8f512803e..e1bfff1fb328 100644
> --- a/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_main.c
> @@ -2473,6 +2473,9 @@ static void mlx5e_close_queues(struct mlx5e_channel *c)
>  	mlx5e_close_tx_cqs(c);
>  	mlx5e_close_cq(&c->icosq.cq);
>  	mlx5e_close_cq(&c->async_icosq.cq);
> +
> +	netif_queue_set_napi(c->netdev, c->ix, NETDEV_QUEUE_TYPE_TX, NULL);
> +	netif_queue_set_napi(c->netdev, c->ix, NETDEV_QUEUE_TYPE_RX, NULL);

This should be set to NULL *before* actually closing the rqs, sqs, and
related cqs right? I would expect these two lines to be the first ones
called in mlx5e_close_queues. Btw, I think this should be done in
mlx5e_deactivate_channel where the NAPI is disabled.

>  }
>  
>  static u8 mlx5e_enumerate_lag_port(struct mlx5_core_dev *mdev, int ix)
> @@ -2558,6 +2561,7 @@ static int mlx5e_open_channel(struct mlx5e_priv *priv, int ix,
>  	c->stats    = &priv->channel_stats[ix]->ch;
>  	c->aff_mask = irq_get_effective_affinity_mask(irq);
>  	c->lag_port = mlx5e_enumerate_lag_port(priv->mdev, ix);
> +	c->irq		= irq;
>  
>  	netif_napi_add(netdev, &c->napi, mlx5e_napi_poll);
>  
> @@ -2602,6 +2606,10 @@ static void mlx5e_activate_channel(struct mlx5e_channel *c)
>  		mlx5e_activate_xsk(c);
>  	else
>  		mlx5e_activate_rq(&c->rq);
> +
> +	netif_napi_set_irq(&c->napi, c->irq);
> +	netif_queue_set_napi(c->netdev, c->ix, NETDEV_QUEUE_TYPE_TX, &c->napi);
> +	netif_queue_set_napi(c->netdev, c->ix, NETDEV_QUEUE_TYPE_RX, &c->napi);

It's weird that netlink queue API is being configured in
mlx5e_activate_channel and deconfigured in mlx5e_close_queues. This
leads to a problem where the napi will be falsely referred to even when
we deactivate the channels in mlx5e_switch_priv_channels and may not
necessarily get to closing the channels due to an error.

Typically, we use the following clean up patterns.

mlx5e_activate_channel -> mlx5e_deactivate_channel
mlx5e_open_queues -> mlx5e_close_queues

>  }
>  
>  static void mlx5e_deactivate_channel(struct mlx5e_channel *c)

--
Thanks,

Rahul Rameshbabu