Re: [dpdk-stable] [PATCH 1/2] net/mlx5: fix return value of start operation

[Olivier Matz <olivier.matz@6wind.com>]

On Fri, Jan 19, 2018 at 09:43:14AM +0100, Olivier Matz wrote:
> On Fri, Jan 19, 2018 at 09:35:01AM +0100, Nélio Laranjeiro wrote:
> > On Thu, Jan 18, 2018 at 05:13:08PM +0100, Olivier Matz wrote:
> > > On Thu, Jan 18, 2018 at 05:04:27PM +0100, Nélio Laranjeiro wrote:
> > > > On Thu, Jan 18, 2018 at 02:00:42PM +0100, Olivier Matz wrote:
> > > > > On error, mlx5_dev_start() does not return a negative value
> > > > > as it is supposed to do. The consequence is that the application
> > > > > (ex: testpmd) does not notice that the port is not started
> > > > > and begins the rxtx on an uninitialized port, which crashes.
> > > > > 
> > > > > Fixes: e1016cb73383 ("net/mlx5: fix Rx interrupts management")
> > > > > Cc: stable@dpdk.org
> > > > > 
> > > > > Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
> > > > > ---
> > > > >  drivers/net/mlx5/mlx5_trigger.c | 4 +++-
> > > > >  1 file changed, 3 insertions(+), 1 deletion(-)
> > > > > 
> > > > > diff --git a/drivers/net/mlx5/mlx5_trigger.c b/drivers/net/mlx5/mlx5_trigger.c
> > > > > index 1a20967a2..44f702daa 100644
> > > > > --- a/drivers/net/mlx5/mlx5_trigger.c
> > > > > +++ b/drivers/net/mlx5/mlx5_trigger.c
> > > > > @@ -166,6 +166,7 @@ mlx5_dev_start(struct rte_eth_dev *dev)
> > > > >  		ERROR("%p: an error occurred while configuring control flows:"
> > > > >  		      " %s",
> > > > >  		      (void *)priv, strerror(err));
> > > > > +		err = -err;
> > > > >  		goto error;
> > > > >  	}
> > > > >  	err = priv_flow_start(priv, &priv->flows);
> > > > > @@ -173,6 +174,7 @@ mlx5_dev_start(struct rte_eth_dev *dev)
> > > > >  		ERROR("%p: an error occurred while configuring flows:"
> > > > >  		      " %s",
> > > > >  		      (void *)priv, strerror(err));
> > > > > +		err = -err;
> > > > >  		goto error;
> > > > >  	}
> > > > >  	err = priv_rx_intr_vec_enable(priv);
> > > > > @@ -196,7 +198,7 @@ mlx5_dev_start(struct rte_eth_dev *dev)
> > > > >  	priv_rxq_stop(priv);
> > > > >  	priv_flow_delete_drop_queue(priv);
> > > > >  	priv_unlock(priv);
> > > > > -	return -err;
> > > > > +	return err;
> > > > >  }
> > > > >  
> > > > >  /**
> > > > 
> > > > err in the function is handled with positives errno's, adding only those
> > > > two and returning err will make the other positive.
> > > 
> > > I tried to check the return value of all functions called by mlx5_dev_start()
> > > (negative or positive). Do you see something wrong?
> > 
> > What I mean is priv_flow_start() is returning a positive errno as all
> > other functions priv_*() that's the main reason for the final rteurn -err;

priv_txq_start(priv);
  -> negative on error
priv_rxq_start(priv);
  -> negative on error
priv_dev_traffic_enable(priv, dev);
  -> positive (+errno) on error
priv_flow_start(priv, &priv->flows);
  -> positive (+errno) on error
priv_rx_intr_vec_enable(priv);
  -> negative (-1 or -errno) on error


> > Internally MLX5 driver only works with positives errnos as lot of them
> > are retuning the values from ioctl directly.  Only the public ones are
> > returning negatives.
> 
> So, what should I modify in this patch for v2?
> Do you agree that there is a bug regarding the return value of mlx5_dev_start()?
> 
> It can be reproduced easily by starting testpmd on a dual-socket machine,
> use the core and memory from socket 0, and have the mlx device on socket 1.
> Then start traffic forwarding, it will crash.