netdev - Re: [PATCH net-next 2/2] ibmvnic: add sysfs entry for timeout and fatal reset

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Date:   Mon, 12 Apr 2021 19:49:36 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Lijun Pan <lijunp213@...il.com>
Cc:     netdev@...r.kernel.org
Subject: Re: [PATCH net-next 2/2] ibmvnic: add sysfs entry for timeout and
 fatal reset

On Mon, 12 Apr 2021 15:26:00 -0500 Lijun Pan wrote:
> On Mon, Apr 12, 2021 at 1:23 PM Jakub Kicinski <kuba@...nel.org> wrote:
> > On Mon, 12 Apr 2021 02:43:30 -0500 Lijun Pan wrote:  
> > > Add timeout and fatal reset sysfs entries so that both functions
> > > can be triggered manually the tested. Otherwise, you have to run
> > > the program for enough time and check both randomly generated
> > > resets in the long long log.  
> >
> > This looks more suitable for debugfs.
> >
> > But can't you use ethtool or devlink reset functionality somehow?  
> 
> ethtool and devlink reset seem better to be implemented by a FAILVOER reset for
> this driver. ethtool/devlink reset are not implemented in this driver,
> which will be a todo list for me.

ethtool isn't really much to implement, its basically a bunch of ops
the driver implements. You can pick and choose which ones you implement.

It'd be better to use ethtool or devlink, but I guess debugfs could be
acceptable too. sysfs is a stable API, so it's definitely a no-go.

> This timeout reset can be triggered by tx watchdog,
> .ndo_tx_timeout->ibmvnic_tx_timeout->ibmvnic_reset(adapter, VNIC_RESET_TIMEOUT);
> Do you know is there a way to trigger that ndo_tx_timeout from some
> user space tool?
> 
> The FATAL reset is triggered by Firmware, quite specific for this driver.
> So in order to verify that, I put it in sysfs entry.

Good question, I don't think we have a way to trigger the timeout 
in a generic way. My first instinct would be to use ethtool self test
(ethtool_ops->self_test) to call the same function within the driver.