Re: [PATCH net-next v2] net: mana: Handle SKB if TX SGEs exceed hardware limit

[Aditya Garg]

On 01-11-2025 04:56, Jakub Kicinski wrote:
> On Wed, 29 Oct 2025 06:12:35 -0700 Aditya Garg wrote:
> > @@ -289,6 +290,21 @@ netdev_tx_t mana_start_xmit(struct sk_buff *skb, struct net_device *ndev)
> >   	cq = &apc->tx_qp[txq_idx].tx_cq;
> >   	tx_stats = &txq->stats;
> >   
> > +	if (MAX_SKB_FRAGS + 2 > MAX_TX_WQE_SGL_ENTRIES &&
> > +	    skb_shinfo(skb)->nr_frags + 2 > MAX_TX_WQE_SGL_ENTRIES) {
> > +		/* GSO skb with Hardware SGE limit exceeded is not expected here
> > +		 * as they are handled in mana_features_check() callback
> > +		 */
> > +		if (skb_is_gso(skb))
> > +			netdev_warn_once(ndev, "GSO enabled skb exceeds max SGE limit\n");
>
> This could be the same question Simon asked but why do you think you
> need this line? Sure you need to linearize non-GSO but why do you care
> to warn specifically about GSO?! Looks like defensive programming or
> testing leftover..
Hi Jakub,
Agreed, The GSO specific warning is redundant. I'll drop it in next 
revision.
> > +		if (skb_linearize(skb)) {
> > +			netdev_warn_once(ndev, "Failed to linearize skb with nr_frags=%d and is_gso=%d\n",
> > +					 skb_shinfo(skb)->nr_frags,
> > +					 skb_is_gso(skb));
>
> .. in practice including is_gso() here as you do is probably enough for
> debug
Ok
> > +			goto tx_drop_count;
> > +		}
> > +	}
> > +
> >   	pkg.tx_oob.s_oob.vcq_num = cq->gdma_id;
> >   	pkg.tx_oob.s_oob.vsq_frame = txq->vsq_frame;
> >   
> > @@ -402,8 +418,6 @@ netdev_tx_t mana_start_xmit(struct sk_buff *skb, struct net_device *ndev)
> >   		}
> >   	}
> >   
> > -	WARN_ON_ONCE(pkg.wqe_req.num_sge > MAX_TX_WQE_SGL_ENTRIES);
> > -
> >   	if (pkg.wqe_req.num_sge <= ARRAY_SIZE(pkg.sgl_array)) {
> >   		pkg.wqe_req.sgl = pkg.sgl_array;
> >   	} else {
> > @@ -438,9 +452,13 @@ netdev_tx_t mana_start_xmit(struct sk_buff *skb, struct net_device *ndev)
> >   
> >   	if (err) {
> >   		(void)skb_dequeue_tail(&txq->pending_skbs);
> > +		mana_unmap_skb(skb, apc);
> >   		netdev_warn(ndev, "Failed to post TX OOB: %d\n", err);
>
> You have a print right here and in the callee. This condition must
> (almost) never happen in practice. It's likely fine to just drop
> the packet.
> The logs placed in callee doesn't covers all the failure scenarios, 
hence I feel to have this log here with proper status. Maybe I can 
remove the log in the callee?

> Either way -- this should be a separate patch.
Are you suggesting a separate patch altogether or two patch in the same 
series?

Based on your suggestion i can work on v3.
Regards,
Aditya

> > -		err = NETDEV_TX_BUSY;
> > -		goto tx_busy;
> > +		if (err == -ENOSPC) {
> > +			err = NETDEV_TX_BUSY;
> > +			goto tx_busy;
> > +		}
> > +		goto free_sgl_ptr;
> >   	}
> >   
> >   	err = NETDEV_TX_OK;
> > @@ -478,6 +496,25 @@ netdev_tx_t mana_start_xmit(struct sk_buff *skb, struct net_device *ndev)
> >   	return NETDEV_TX_OK;
> >   }