Re: [net-next PATCH v3 3/8] net: sched: add cls_u32 offload hooks for netdevs

[Simon Horman <simon.horman@netronome.com>]

On Thu, Feb 18, 2016 at 11:23:35AM +0200, Amir Vadai" wrote:
> On Wed, Feb 17, 2016 at 03:07:23PM -0800, John Fastabend wrote:
> > [...]
> > 
> > >>
> > >>> +static void u32_replace_hw_hnode(struct tcf_proto *tp, struct
> > >>> tc_u_hnode *h)
> > >>> +{
> > >>> +    struct net_device *dev = tp->q->dev_queue->dev;
> > >>> +    struct tc_cls_u32_offload u32_offload = {0};
> > >>> +    struct tc_to_netdev offload;
> > >>> +
> > >>> +    offload.type = TC_SETUP_CLSU32;
> > >>> +    offload.cls_u32 = &u32_offload;
> > >>> +
> > >>> +    if (dev->netdev_ops->ndo_setup_tc) {
> > >>> +        offload.cls_u32->command = TC_CLSU32_NEW_HNODE;
> > >>
> > >> TC_CLSU32_REPLACE_HNODE?
> > >>
> > > 
> > > Yep I made this change and will send out v4.
> > > 
> > > [...]
> > > 
> > >>
> > 
> > Actually thinking about this a bit more I wrote this thinking
> > that there existed some hardware that actually cared if it was
> > a new rule or an existing rule. For me it doesn't matter I do
> > the same thing in the new/replace cases I just write into the
> > slot on the hardware table and if it happens to have something
> > in it well its overwritten e.g. "replaced". This works because
> > the cls_u32 layer protects us from doing something unexpected.
> > 
> > I'm wondering (mostly asking the mlx folks) is there hardware
> > out there that cares to make this distinction between new and
> > replace? Otherwise I can just drop new and always use replace.
> > Or vice versa which is the case in its current form.
> I don't see a need for such a distinction in mlx hardware.

FWIW, I think it is unlikely such a distinction would
be needed for Netronome hardware.