netdev - Re: [PATCH net-next] mlx4: make sure to always set the port type

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Date:   Sun, 6 Sep 2020 09:33:05 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Leon Romanovsky <leon@...nel.org>
Cc:     davem@...emloft.net, netdev@...r.kernel.org, kernel-team@...com,
        tariqt@...lanox.com, yishaih@...lanox.com,
        linux-rdma@...r.kernel.org, jiri@...nulli.us
Subject: Re: [PATCH net-next] mlx4: make sure to always set the port type

On Sun, 6 Sep 2020 10:27:59 +0300 Leon Romanovsky wrote:
> On Fri, Sep 04, 2020 at 01:06:21PM -0700, Jakub Kicinski wrote:
> > Even tho mlx4_core registers the devlink ports, it's mlx4_en
> > and mlx4_ib which set their type. In situations where one of
> > the two is not built yet the machine has ports of given type
> > we see the devlink warning from devlink_port_type_warn() trigger.
> >
> > Having ports of a type not supported by the kernel may seem
> > surprising, but it does occur in practice - when the unsupported
> > port is not plugged in to a switch anyway users are more than happy
> > not to see it (and potentially allocate any resources to it).
> >
> > Set the type in mlx4_core if type-specific driver is not built.
> >
> > Signed-off-by: Jakub Kicinski <kuba@...nel.org>
> > ---
> >  drivers/net/ethernet/mellanox/mlx4/main.c | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> >
> > diff --git a/drivers/net/ethernet/mellanox/mlx4/main.c b/drivers/net/ethernet/mellanox/mlx4/main.c
> > index 258c7a96f269..70cf24ba71e4 100644
> > --- a/drivers/net/ethernet/mellanox/mlx4/main.c
> > +++ b/drivers/net/ethernet/mellanox/mlx4/main.c
> > @@ -3031,6 +3031,17 @@ static int mlx4_init_port_info(struct mlx4_dev *dev, int port)
> >  	if (err)
> >  		return err;
> >
> > +	/* Ethernet and IB drivers will normally set the port type,
> > +	 * but if they are not built set the type now to prevent
> > +	 * devlink_port_type_warn() from firing.
> > +	 */
> > +	if (!IS_ENABLED(CONFIG_MLX4_EN) &&
> > +	    dev->caps.port_type[port] == MLX4_PORT_TYPE_ETH)
> > +		devlink_port_type_eth_set(&info->devlink_port, NULL);  
>                                                                ^^^^^
> 
> Won't it crash in devlink_port_type_eth_set()?
> The first line there dereferences pointer.
>   7612         const struct net_device_ops *ops = netdev->netdev_ops;

Damn, good catch. It's not supposed to be required. I'll patch devlink.
 
> And can we call to devlink_port_type_*_set() without IS_ENABLED() check?

It'll generate two netlink notifications - not the end of the world but
also doesn't feel super clean.