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

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Message-ID: <20200907062135.GJ2997@nanopsycho.orion>
Date:   Mon, 7 Sep 2020 08:21:35 +0200
From:   Jiri Pirko <jiri@...nulli.us>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     Leon Romanovsky <leon@...nel.org>, davem@...emloft.net,
        netdev@...r.kernel.org, kernel-team@...com, tariqt@...lanox.com,
        yishaih@...lanox.com, linux-rdma@...r.kernel.org
Subject: Re: [PATCH net-next] mlx4: make sure to always set the port type

Sun, Sep 06, 2020 at 06:33:05PM CEST, kuba@...nel.org wrote:
>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.

When you set the port type to ethernet, you should have the net_device
instance. Why wouldn't you?


> 
>> 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.