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 08:32:02 -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 8:01 AM, Hal Rosenstock wrote:
> 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 ?

I just noticed that you reference 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.

Should the fix be to hw/mlx5/main.c:translate_eth_proto_oper which now has:

        switch (eth_proto_oper) {
...
        default:
                return -EINVAL;
        }

        return 0;

and change default case to:
		*active_width = IB_WIDTH_1X;

?

> -- 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,
>>