Subject: Re: [PATCH net-next V2 01/10] net/flower: Introduce hardware offload support

From: John Fastabend <[email-masked]>
Date: Fri, 04 Mar 2016 09:01:39 -0800

On 16-03-03 06:55 AM, Amir Vadai wrote:
> This patch is based on a patch made by John Fastabend.
> It adds support for offloading cls_flower.
> when NETIF_F_HW_TC is on:
>   flags = 0       => Rule will be processed twice - by hardware, and if
>                      still relevant, by software.
>   flags = SKIP_HW => Rull will be processed by software only
> 
> If hardare fail/not capabale to apply the rule, operation will fail.
> 
> Suggested-by: John Fastabend <[email-masked]>
> Signed-off-by: Amir Vadai <[email-masked]>
> ---

[...]

>  static bool fl_destroy(struct tcf_proto *tp, bool force)
>  {
>  	struct cls_fl_head *head = rtnl_dereference(tp->root);
> @@ -174,6 +220,7 @@ static bool fl_destroy(struct tcf_proto *tp, bool force)
>  		return false;
>  
>  	list_for_each_entry_safe(f, next, &head->filters, list) {
> +		fl_hw_destroy_filter(tp, (u64)f);
>  		list_del_rcu(&f->list);
>  		call_rcu(&f->rcu, fl_destroy_filter);
>  	}
> @@ -454,11 +501,13 @@ static int fl_change(struct net *net, struct sk_buff *in_skb,
>  		     u32 handle, struct nlattr **tca,
>  		     unsigned long *arg, bool ovr)
>  {
> +	struct net_device *dev = tp->q->dev_queue->dev;
>  	struct cls_fl_head *head = rtnl_dereference(tp->root);
>  	struct cls_fl_filter *fold = (struct cls_fl_filter *) *arg;
>  	struct cls_fl_filter *fnew;
>  	struct nlattr *tb[TCA_FLOWER_MAX + 1];
>  	struct fl_flow_mask mask = {};
> +	u32 flags = 0;
>  	int err;
>  
>  	if (!tca[TCA_OPTIONS])
> @@ -486,6 +535,9 @@ static int fl_change(struct net *net, struct sk_buff *in_skb,
>  	}
>  	fnew->handle = handle;
>  
> +	if (tb[TCA_FLOWER_FLAGS])
> +		flags = nla_get_u32(tb[TCA_FLOWER_FLAGS]);
> +
>  	err = fl_set_parms(net, tp, fnew, &mask, base, tb, tca[TCA_RATE], ovr);
>  	if (err)
>  		goto errout;
> @@ -498,9 +550,22 @@ static int fl_change(struct net *net, struct sk_buff *in_skb,
>  				     head->ht_params);
>  	if (err)
>  		goto errout;
> -	if (fold)
> +
> +	err = fl_hw_replace_filter(tp,
> +				   &head->dissector,
> +				   &mask.key,
> +				   &fnew->key,
> +				   &fnew->exts,
> +				   (u64)fnew,
> +				   flags);
> +	if (err)
> +		goto err_hash_remove;
> +

This behaviour is different than how I did u32 in the u32 case I just
let the software case get loaded and do not throw any errors. The
intent was if we required a HW entry we would explicitly state that
with the SKIP_SW (to be implemented) flag. This error path seems
to block the software filter when the hardware fails.

I think it would be best to do the same as u32 here and use the error
path only if SKIP_SW is set. Or if you really want an error path on
SW/HW loads then use another bit in the flag to specify STRICT or
something along those lines.

> +	if (fold) {
>  		rhashtable_remove_fast(&head->ht, &fold->ht_node,
>  				       head->ht_params);
> +		fl_hw_destroy_filter(tp, (u64)fold);
> +	}
>  
>  	*arg = (unsigned long) fnew;
>  
> @@ -514,6 +579,9 @@ static int fl_change(struct net *net, struct sk_buff *in_skb,
>  
>  	return 0;
>  
> +err_hash_remove:
> +	rhashtable_remove_fast(&head->ht, &fnew->ht_node, head->ht_params);
> +
>  errout:
>  	kfree(fnew);
>  	return err;
> @@ -527,6 +595,7 @@ static int fl_delete(struct tcf_proto *tp, unsigned long arg)
>  	rhashtable_remove_fast(&head->ht, &f->ht_node,
>  			       head->ht_params);
>  	list_del_rcu(&f->list);
> +	fl_hw_destroy_filter(tp, (u64)f);
>  	tcf_unbind_filter(tp, &f->res);
>  	call_rcu(&f->rcu, fl_destroy_filter);
>  	return 0;
>