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

From: Joe Damato <[email-masked]>
Date: Mon, 5 Feb 2024 17:32:47 -0800

On Mon, Feb 05, 2024 at 05:09:09PM -0800, Rahul Rameshbabu wrote:
> On Tue, 06 Feb, 2024 01:03:11 +0000 Joe Damato <[email-masked]> wrote:
> > Make mlx5 compatible with the newly added netlink queue GET APIs.
> >
> > Signed-off-by: Joe Damato <[email-masked]>
> > ---
> >  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

OK, I'll move it to mlx5e_deactivate_channel before the NAPI is disabled.
That makes sense to me.