linux-kernel - Re: [PATCH 2/2] IB/core: Set width to 1X for invalid active widths when port is down

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Date:   Thu, 15 Mar 2018 08:01:08 -0400
From:   Hal Rosenstock <hal@....mellanox.co.il>
To:     Honggang LI <honli@...hat.com>, dledford@...hat.com, jgg@...pe.ca,
        linux-rdma@...r.kernel.org
Cc:     noaos@...lanox.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] IB/core: Set width to 1X for invalid active widths
 when port is down

On 3/15/2018 5:02 AM, Honggang LI wrote:
> From: Honggang Li <honli@...hat.com>
> 
> commit f1b65df5a232 ("IB/mlx5: Add support for active_width and
> active_speed in RoCE"). Before this patch applied, the mlx5_ib
> driver set default active_width and active_speed to IB_WIDTH_4X
> and IB_SPEED_QDR.
> 
> When the RoCE port is down, the RoCE port did not negotiate the
> active width with remote side. The active width is zero. If run
> ibstat to require the port status, ibstat will panic as it read
> invalid width from sys file.
> 
> Signed-off-by: Honggang Li <honli@...hat.com>
> ---
>  drivers/infiniband/core/sysfs.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/infiniband/core/sysfs.c b/drivers/infiniband/core/sysfs.c
> index cf36ff1f0068..722e4571f4d2 100644
> --- a/drivers/infiniband/core/sysfs.c
> +++ b/drivers/infiniband/core/sysfs.c
> @@ -240,6 +240,7 @@ static ssize_t rate_show(struct ib_port *p, struct port_attribute *unused,
>  	struct ib_port_attr attr;
>  	char *speed = "";
>  	int rate;		/* in deci-Gb/sec */
> +	int width;
>  	ssize_t ret;
>  
>  	ret = ib_query_port(p->ibdev, p->port_num, &attr);
> @@ -278,13 +279,19 @@ static ssize_t rate_show(struct ib_port *p, struct port_attribute *unused,
>  		break;
>  	}
>  
> -	rate *= ib_width_enum_to_int(attr.active_width);
> -	if (rate < 0)
> -		return -EINVAL;
> +	width = ib_width_enum_to_int(attr.active_width);
> +	if (width < 0) {
> +		if (attr.state != IB_PORT_ACTIVE)

Link width is valid in any PortState other than Down so I think that
this check should be:
		if (attr.state != IB_PORT_DOWN)

However, I don't think overriding width should be needed for this case
and just returning -EINVAL should be fine regardless of port state.
AFAIK it's the driver responsibility to populate acceptable defaults for
such parameters. What driver(s) have this issue ? Shouldn't it be fixed
there rather than here ?

-- Hal

> +			width = 1; /* default to 1X for invalid widths */
> +		else
> +			return -EINVAL;
> +	}
> +
> +	rate *= width;
>  
>  	return sprintf(buf, "%d%s Gb/sec (%dX%s)\n",
>  		       rate / 10, rate % 10 ? ".5" : "",
> -		       ib_width_enum_to_int(attr.active_width), speed);
> +		       width, speed);
>  }
>  
>  static ssize_t phys_state_show(struct ib_port *p, struct port_attribute *unused,
>