Re: [PATCH net-next v3 1/2] net: ethernet: Allow disabling pause on panic

[Florian Fainelli]

On 11/10/25 17:10, Jakub Kicinski wrote:
> On Thu,  6 Nov 2025 16:25:09 -0800 Florian Fainelli wrote:
> > Development devices on a lab network might be subject to kernel panics
> > and if they have pause frame generation enabled, once the kernel panics,
> > the Ethernet controller stops being serviced. This can create a flood of
> > pause frames that certain switches are unable to handle resulting a
> > completle paralysis of the network because they broadcast to other
> > stations on that same network segment.
> >
> > To accomodate for such situation introduce a
> > /sys/class/net/<device>/disable_pause_on_panic knob which will disable
> > Ethernet pause frame generation upon kernel panic.
> >
> > Note that device driver wishing to make use of that feature need to
> > implement ethtool_ops::set_pauseparam_panic to specifically deal with
> > that atomic context.
>
> Some basic review comments below (no promises if addressing those will
> make me for one feel any warmer towards the concept).
>
> >   Documentation/ABI/testing/sysfs-class-net | 16 +++++
> >   include/linux/ethtool.h                   |  3 +
> >   include/linux/netdevice.h                 |  1 +
> >   net/core/net-sysfs.c                      | 39 +++++++++++
> >   net/ethernet/Makefile                     |  3 +-
> >   net/ethernet/pause_panic.c                | 79 +++++++++++++++++++++++
>
> panic.c or shutdown.c is probably a slightly better name,
> more likely we'd add more code in that.
>
> >   6 files changed, 140 insertions(+), 1 deletion(-)
> >   create mode 100644 net/ethernet/pause_panic.c
> >
> > diff --git a/Documentation/ABI/testing/sysfs-class-net b/Documentation/ABI/testing/sysfs-class-net
> > index ebf21beba846..da0e4e862aca 100644
> > --- a/Documentation/ABI/testing/sysfs-class-net
> > +++ b/Documentation/ABI/testing/sysfs-class-net
> > @@ -352,3 +352,19 @@ Description:
> >   		0  threaded mode disabled for this dev
> >   		1  threaded mode enabled for this dev
> >   		== ==================================
> > +
> > +What:		/sys/class/net/<iface>/disable_pause_on_panic
> > +Date:		Nov 2025
> > +KernelVersion:	6.20
> > +Contact:	netdev@xxxxxxxxxxxxxxx
> > +Description:
> > +		Boolean value to control whether to disable pause frame
> > +		generation on panic. This is helpful in environments where
> > +		the link partner may incorrect respond to pause frames (e.g.:
> > +		improperly configured Ethernet switches)
> > +
> > +		Possible values:
> > +		== =====================================================
> > +		0  do not disable pause frame generation on kernel panic
> > +		1  disable pause frame generation on kernel panic
> > +		== =====================================================
>
> please no sysfs for something as niche as this feature

Would you prefer ethtool in that case?
--
Florian