Re: [dpdk-stable] [PATCH v1] net/failsafe: fix VLAN stripping configuration

[Ophir Munk <ophirmu@mellanox.com>]

Hi,
Please see below

> -----Original Message-----
> From: Gaëtan Rivet [mailto:gaetan.rivet@6wind.com]
> Sent: Thursday, November 02, 2017 4:16 PM
> To: Ophir Munk <ophirmu@mellanox.com>
> Cc: dev@dpdk.org; Thomas Monjalon <thomas@monjalon.net>; Olga Shern
> <olgas@mellanox.com>; stable@dpdk.org
> Subject: Re: [PATCH v1] net/failsafe: fix VLAN stripping configuration
> 
> On Thu, Nov 02, 2017 at 02:52:16PM +0100, Gaëtan Rivet wrote:
> > On Wed, Nov 01, 2017 at 08:12:38PM +0000, Ophir Munk wrote:
> > > failsafe device has vlan stripping configured at startup however
> > > once a sub device is found as non-capable of vlan-stripping failsafe
> > > updates it configuration and removes vlan stripping from it.
> > > This update occurs only once at startup. Following a later plugin
> > > attempt and in case of vlan stripping mismatch between failsafe
> > > configuration and device capability - failsafe cannot recover and
> > > the device remains constantly in plug out state.
> > >
> > > The sequence of events leading to this situation is described as
> > > follows:
> > > 1. Start testpmd with failsafe where mlx4 is a sub device (not
> > > capable of vlan stripping). Expected printout:
> > > PMD: net_failsafe: Disabling VLAN stripping offload 2. Execute:
> > > testpmd> port stop all
> > > testpmd> port config all max-pkt-len 2048 port start all
> > > 3. Do a plug out (e.g. disable sriov) 4. Do a plug in (e.g. enable
> > > sriov) 5. Expected result: failsafe successfully configures and
> > > starts its sub devices Actual result: failsafe is continuously
> > > failing with these messages:
> > > PMD: net_failsafe: VLAN stripping offload requested but not
> > > supported by sub_device 0
> > > PMD: net_failsafe: device already configured, cannot fix live
> > > configuration
> > > PMD: net_failsafe: Unable to synchronize sub device state
> > >
> > > Root cause analysis: at startup failsafe removes vlan stripping from
> > > its configuration. After executing "port config all max-pkt-len 2048"
> > > testpmd marks failsafe in need for configuration update.
> > > After executing "port start all" testpmd overrides failsafe
> > > configuration with its own configuration which includes vlan
> > > stripping
> > >
> >
> > Have you tried launching testpmd with the option
> >
> > "--disable-hw-vlan"
> >
> > as your mlx4 port does not support it?
> >
> 
> On a second thought, I think there is a simple solution:
> 
> The fail-safe should stop trying to be clever with port configuration.
> On rte_eth_dev_configure, simply apply the user configuration (without
> trying to detect support and disabling flags on the fly).
> 
> If a PMD has an issue, it should warn the user. If it has an issue but does not
> warn, it is a bug for this PMD. This is the case for MLX4:
> either the PMD changes its behavior, or not, as long as users are fine with it.
> 
> So a proper fix would be to remove the checks (fs_port_offload_validate and
> fs_port_disable_offload) and depend on the sub-device for proper
> configuration vetting.
> 
> Thoughts?

Agreed. I have sent v2 based on your suggestion. 

> 
> > > During the plugin attempt failsafe refuses to update its
> > > configuration by removing vlan stripping since it has already
> > > updated its configuration at startup.
> > >
> > > The fix is to remove the limitation of one time configuration at
> > > startup and allow it during plugin attempts.
> > >
> > > Cc: stable@dpdk.org
> > > Fixes: bbc6a53dda44 ("net/failsafe: support Rx offload
> > > capabilities")
> > >
> > > Signed-off-by: Ophir Munk <ophirmu@mellanox.com>
> > > ---
> > > The commit message includes bug and fix descriptions
> > > ---
> > >  drivers/net/failsafe/failsafe_ops.c | 10 ----------
> > >  1 file changed, 10 deletions(-)
> > >
> > > diff --git a/drivers/net/failsafe/failsafe_ops.c
> > > b/drivers/net/failsafe/failsafe_ops.c
> > > index f460551..953ee65 100644
> > > --- a/drivers/net/failsafe/failsafe_ops.c
> > > +++ b/drivers/net/failsafe/failsafe_ops.c
> > > @@ -187,16 +187,6 @@
> > >  			continue;
> > >  		DEBUG("Checking capabilities for sub_device %d", i);
> > >  		while ((capa_flag = fs_port_offload_validate(dev, sdev))) {
> > > -			/*
> > > -			 * Refuse to change configuration if multiple devices
> > > -			 * are present and we already have configured at
> least
> > > -			 * some of them.
> > > -			 */
> > > -			if (PRIV(dev)->state >= DEV_ACTIVE &&
> > > -			    PRIV(dev)->subs_tail > 1) {
> > > -				ERROR("device already configured, cannot
> fix live configuration");
> > > -				return -1;
> > > -			}
> > >  			ret = fs_port_disable_offload(&dev->data-
> >dev_conf,
> > >  						      capa_flag);
> > >  			if (ret) {
> > > --
> > > 1.8.3.1
> > >
> >
> > --
> > Gaëtan Rivet
> > 6WIND
> 
> --
> Gaëtan Rivet
> 6WIND