Re: [dpdk-dev] [PATCH v1] net/mlx4: fix 'show port info all' during detach

["Gaëtan Rivet" <gaetan.rivet@6wind.com>]

Hi Ophir, Adrien,

On Fri, Mar 02, 2018 at 08:12:58PM +0100, Adrien Mazarguil wrote:
> On Wed, Feb 28, 2018 at 04:47:30PM +0000, Ophir Munk wrote:
> > The following scenario causes a crash in function mlx4_get_ifname
> > 1. On testpmd startup mlx4 device is probed and started
> > 2. mlx4 sriov is disabled. As a result an RMV event is sent to
> > testpmd which closes the device and nullify the priv struct
> > members.
> > 3. Running 'show port info all' in testpmd results in segmentation
> > fault because of accessing NULL pointer priv->ctx
> > 
> > The fix is to return with an error from mlx4_get_ifname() if priv->ctx
> > member is NULL.
> 
> So priv->ctx is NULL after mlx4_dev_close() was called. In my opinion the
> fact testpmd is allowed to call rte_eth_dev_info_get() on a closed port is
> fishy, there are quite a few other ethdev callbacks that may end up
> crashing in such a scenario.
> 
> Since commit 284c908cc588 ("app/testpmd: request device removal interrupt"),
> testpmd automatically calls rte_eth_dev_close() and rte_eal_dev_detach()
> after receiving a removal event on a port.
> 
> rte_eth_dev_close() documentation says:
> 
>  "Close a stopped Ethernet device. The device cannot be restarted!
>   The function frees all resources except for needed by the
>   closed state. To free these resources, call rte_eth_dev_detach()."
> 
> Unfortunately testpmd calls rte_*eal*_dev_detach() not
> rte_*eth*_dev_detach(), the former doesn't release ethdev ports while the
> latter does. I think it's a mistake, there's no point in keeping a closed
> device around after it's been physically unplugged.
> 
> In short, rmv_event_callback() should call detach_port() instead of
> rte_eal_dev_detach().
> 

This is correct, the issue is actually testpmd making a mistake when
calling directly rte_eal_dev_detach().

The fix should thus be simply to change this call.

> > Fixes: 61cbdd419478 ("net/mlx4: separate device control functions")
> > Cc: stable@dpdk.org
> > 
> > Signed-off-by: Ophir Munk <ophirmu@mellanox.com>
> 
> The above suggests the problem is actually in testpmd and was introduced in
> v17.05 by commit 284c908cc588. The proposed patch is a workaround that
> doesn't address the underlying issue, thus NACK unless proven otherwise :)
> 
> > ---
> >  drivers/net/mlx4/mlx4_ethdev.c | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/net/mlx4/mlx4_ethdev.c b/drivers/net/mlx4/mlx4_ethdev.c
> > index 3bc6927..cca5223 100644
> > --- a/drivers/net/mlx4/mlx4_ethdev.c
> > +++ b/drivers/net/mlx4/mlx4_ethdev.c
> > @@ -67,6 +67,9 @@ mlx4_get_ifname(const struct priv *priv, char (*ifname)[IF_NAMESIZE])
> >  	char match[IF_NAMESIZE] = "";
> >  
> >  	{
> > +		if (priv->ctx == NULL)
> > +			return -ENOENT;
> > +
> >  		MKSTR(path, "%s/device/net", priv->ctx->device->ibdev_path);
> >  
> >  		dir = opendir(path);
> > -- 
> > 2.7.4
> > 
> 
> -- 
> Adrien Mazarguil
> 6WIND

-- 
Gaëtan Rivet
6WIND