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 20:27:39 +0800
From:   Honggang LI <honli@...hat.com>
To:     Hal Rosenstock <hal@....mellanox.co.il>
Cc:     dledford@...hat.com, jgg@...pe.ca, linux-rdma@...r.kernel.org,
        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 Thu, Mar 15, 2018 at 08:01:08AM -0400, 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)

OK, thanks for correct this.

> 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

mlx5_ib, commit f1b65df5a232 changed the default active width and rate.

> there rather than here ?

Yes, I think so, as only mlx5 RoCE impacted by this issue. So, fix the
driver is also acceptable.