netdev - Re: [net-next PATCH v3 3/8] net: sched: add cls

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Date:	Thu, 18 Feb 2016 11:23:35 +0200
From:	"Amir Vadai\"" <amir@...ai.me>
To:	John Fastabend <john.fastabend@...il.com>
Cc:	Jamal Hadi Salim <jhs@...atatu.com>, jiri@...nulli.us,
	davem@...emloft.net, netdev@...r.kernel.org,
	jeffrey.t.kirsher@...el.com
Subject: Re: [net-next PATCH v3 3/8] net: sched: add cls_u32 offload hooks
 for netdevs

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.

Thanks,
Amir.

> 
> Thanks,
> John
>