Subject: Re: [PATCH net-next 3/4] mvpp2: add basic XDP support

From: Maciej Fijalkowski <[email-masked]>
Date: Thu, 2 Jul 2020 11:09:56 +0200

On Thu, Jul 02, 2020 at 11:08:19AM +0300, [email-masked] wrote:
> On Tue, Jun 30, 2020 at 08:09:29PM +0200, Matteo Croce wrote:
> > From: Matteo Croce <[email-masked]>
> > 
> > Add XDP native support.
> > By now only XDP_DROP, XDP_PASS and XDP_REDIRECT
> > verdicts are supported.
> > 
> > Co-developed-by: Sven Auhagen <[email-masked]>
> > Signed-off-by: Sven Auhagen <[email-masked]>
> > Signed-off-by: Matteo Croce <[email-masked]>
> > ---
> 
> [...]
> 
> >  }
> >  
> > +static int
> > +mvpp2_run_xdp(struct mvpp2_port *port, struct mvpp2_rx_queue *rxq,
> > +	      struct bpf_prog *prog, struct xdp_buff *xdp,
> > +	      struct page_pool *pp)
> > +{
> > +	unsigned int len, sync, err;
> > +	struct page *page;
> > +	u32 ret, act;
> > +
> > +	len = xdp->data_end - xdp->data_hard_start - MVPP2_SKB_HEADROOM;
> > +	act = bpf_prog_run_xdp(prog, xdp);
> > +
> > +	/* Due xdp_adjust_tail: DMA sync for_device cover max len CPU touch */
> > +	sync = xdp->data_end - xdp->data_hard_start - MVPP2_SKB_HEADROOM;
> > +	sync = max(sync, len);
> > +
> > +	switch (act) {
> > +	case XDP_PASS:
> > +		ret = MVPP2_XDP_PASS;
> > +		break;
> > +	case XDP_REDIRECT:
> > +		err = xdp_do_redirect(port->dev, xdp, prog);
> > +		if (unlikely(err)) {
> > +			ret = MVPP2_XDP_DROPPED;
> > +			page = virt_to_head_page(xdp->data);
> > +			page_pool_put_page(pp, page, sync, true);
> > +		} else {
> > +			ret = MVPP2_XDP_REDIR;
> > +		}
> > +		break;
> > +	default:
> > +		bpf_warn_invalid_xdp_action(act);
> > +		fallthrough;
> > +	case XDP_ABORTED:
> > +		trace_xdp_exception(port->dev, prog, act);
> > +		fallthrough;
> > +	case XDP_DROP:
> > +		page = virt_to_head_page(xdp->data);
> > +		page_pool_put_page(pp, page, sync, true);
> > +		ret = MVPP2_XDP_DROPPED;
> > +		break;
> > +	}
> > +
> > +	return ret;
> > +}
> > +
> >  /* Main rx processing */
> >  static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi,
> >  		    int rx_todo, struct mvpp2_rx_queue *rxq)
> >  {
> >  	struct net_device *dev = port->dev;
> > +	struct bpf_prog *xdp_prog;
> > +	struct xdp_buff xdp;
> >  	int rx_received;
> >  	int rx_done = 0;
> > +	u32 xdp_ret = 0;
> >  	u32 rcvd_pkts = 0;
> >  	u32 rcvd_bytes = 0;
> >  
> > +	rcu_read_lock();
> > +
> > +	xdp_prog = READ_ONCE(port->xdp_prog);
> > +
> >  	/* Get number of received packets and clamp the to-do */
> >  	rx_received = mvpp2_rxq_received(port, rxq->id);
> >  	if (rx_todo > rx_received)
> > @@ -3060,7 +3115,7 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi,
> >  		dma_addr_t dma_addr;
> >  		phys_addr_t phys_addr;
> >  		u32 rx_status;
> > -		int pool, rx_bytes, err;
> > +		int pool, rx_bytes, err, ret;
> >  		void *data;
> >  
> >  		rx_done++;
> > @@ -3096,6 +3151,33 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi,
> >  		else
> >  			frag_size = bm_pool->frag_size;
> >  
> > +		if (xdp_prog) {
> > +			xdp.data_hard_start = data;
> > +			xdp.data = data + MVPP2_MH_SIZE + MVPP2_SKB_HEADROOM;
> > +			xdp.data_end = xdp.data + rx_bytes;
> > +			xdp.frame_sz = PAGE_SIZE;
> > +
> > +			if (bm_pool->pkt_size == MVPP2_BM_SHORT_PKT_SIZE)
> > +				xdp.rxq = &rxq->xdp_rxq_short;
> > +			else
> > +				xdp.rxq = &rxq->xdp_rxq_long;
> > +
> > +			xdp_set_data_meta_invalid(&xdp);
> > +
> > +			ret = mvpp2_run_xdp(port, rxq, xdp_prog, &xdp, pp);
> > +
> > +			if (ret) {
> > +				xdp_ret |= ret;
> > +				err = mvpp2_rx_refill(port, bm_pool, pp, pool);
> > +				if (err) {
> > +					netdev_err(port->dev, "failed to refill BM pools\n");
> > +					goto err_drop_frame;
> > +				}
> > +
> > +				continue;
> > +			}
> > +		}
> > +
> >  		skb = build_skb(data, frag_size);
> >  		if (!skb) {
> >  			netdev_warn(port->dev, "skb build failed\n");
> > @@ -3118,7 +3200,7 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi,
> >  		rcvd_pkts++;
> >  		rcvd_bytes += rx_bytes;
> >  
> > -		skb_reserve(skb, MVPP2_MH_SIZE + NET_SKB_PAD);
> > +		skb_reserve(skb, MVPP2_MH_SIZE + MVPP2_SKB_HEADROOM);
> >  		skb_put(skb, rx_bytes);
> >  		skb->protocol = eth_type_trans(skb, dev);
> >  		mvpp2_rx_csum(port, rx_status, skb);
> > @@ -3133,6 +3215,8 @@ static int mvpp2_rx(struct mvpp2_port *port, struct napi_struct *napi,
> >  		mvpp2_bm_pool_put(port, pool, dma_addr, phys_addr);
> >  	}
> >  
> > +	rcu_read_unlock();
> > +
> >  	if (rcvd_pkts) {
> >  		struct mvpp2_pcpu_stats *stats = this_cpu_ptr(port->stats);
> >  
> > @@ -3608,6 +3692,8 @@ static void mvpp2_start_dev(struct mvpp2_port *port)
> >  	}
> >  
> >  	netif_tx_start_all_queues(port->dev);
> > +
> > +	clear_bit(0, &port->state);
> >  }
> >  
> >  /* Set hw internals when stopping port */
> > @@ -3615,6 +3701,8 @@ static void mvpp2_stop_dev(struct mvpp2_port *port)
> >  {
> >  	int i;
> >  
> > +	set_bit(0, &port->state);
> > +
> >  	/* Disable interrupts on all threads */
> >  	mvpp2_interrupts_disable(port);
> >  
> > @@ -4021,6 +4109,10 @@ static int mvpp2_change_mtu(struct net_device *dev, int mtu)
> >  	}
> >  
> >  	if (MVPP2_RX_PKT_SIZE(mtu) > MVPP2_BM_LONG_PKT_SIZE) {
> > +		if (port->xdp_prog) {
> > +			netdev_err(dev, "Jumbo frames are not supported with XDP\n");
> 
> Does it make sense to switch to NL_SET_ERR_MSG_MOD() here, so the user can get
> an immediate feedback?

ndo_change_mtu does not provide netlink's extack, so that's not possible
here AFAIK.

> 
> > +			return -EINVAL;
> > +		}
> >  		if (priv->percpu_pools) {
> >  			netdev_warn(dev, "mtu %d too high, switching to shared buffers", mtu);
> >  			mvpp2_bm_switch_buffers(priv, false);
> > @@ -4159,6 +4251,73 @@ static int mvpp2_set_features(struct net_device *dev,
> >  	return 0;
> >  }
> >  
> > +static int mvpp2_xdp_setup(struct mvpp2_port *port, struct netdev_bpf *bpf)
> > +{
> > +	struct bpf_prog *prog = bpf->prog, *old_prog;
> > +	bool running = netif_running(port->dev);
> > +	bool reset = !prog != !port->xdp_prog;
> > +
> > +	if (port->dev->mtu > ETH_DATA_LEN) {
> > +		netdev_err(port->dev, "Jumbo frames are not supported by XDP, current MTU %d.\n",
> > +			   port->dev->mtu);
> 
> ditto

Here I agree and for every other netdev_err within mvpp2_xdp_setup().

> 
> > +		return -EOPNOTSUPP;
> > +	}
> > +
> > +	if (!port->priv->percpu_pools) {
> > +		netdev_err(port->dev, "Per CPU Pools required for XDP");
> > +		return -EOPNOTSUPP;
> > +	}
> > +
> > +	/* device is up and bpf is added/removed, must setup the RX queues */
> > +	if (running && reset) {
> > +		mvpp2_stop_dev(port);
> > +		mvpp2_cleanup_rxqs(port);
> > +		mvpp2_cleanup_txqs(port);
> > +	}
> > +
> > +	old_prog = xchg(&port->xdp_prog, prog);
> > +	if (old_prog)
> > +		bpf_prog_put(old_prog);
> > +
> > +	/* bpf is just replaced, RXQ and MTU are already setup */
> > +	if (!reset)
> > +		return 0;
> > +
> > +	/* device was up, restore the link */
> > +	if (running) {
> > +		int ret = mvpp2_setup_rxqs(port);
> > +
> > +		if (ret) {
> > +			netdev_err(port->dev, "mvpp2_setup_rxqs failed\n");
> > +			return ret;
> > +		}
> > +		ret = mvpp2_setup_txqs(port);
> > +		if (ret) {
> > +			netdev_err(port->dev, "mvpp2_setup_txqs failed\n");
> > +			return ret;
> > +		}
> > +
> > +		mvpp2_start_dev(port);
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int mvpp2_xdp(struct net_device *dev, struct netdev_bpf *xdp)
> > +{
> > +	struct mvpp2_port *port = netdev_priv(dev);
> > +
> > +	switch (xdp->command) {
> > +	case XDP_SETUP_PROG:
> > +		return mvpp2_xdp_setup(port, xdp);
> > +	case XDP_QUERY_PROG:
> > +		xdp->prog_id = port->xdp_prog ? port->xdp_prog->aux->id : 0;
> > +		return 0;
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +}
> > +
> >  /* Ethtool methods */
> >  
> >  static int mvpp2_ethtool_nway_reset(struct net_device *dev)
> > @@ -4509,6 +4668,7 @@ static const struct net_device_ops mvpp2_netdev_ops = {
> >  	.ndo_vlan_rx_add_vid	= mvpp2_vlan_rx_add_vid,
> >  	.ndo_vlan_rx_kill_vid	= mvpp2_vlan_rx_kill_vid,
> >  	.ndo_set_features	= mvpp2_set_features,
> > +	.ndo_bpf		= mvpp2_xdp,
> >  };
> >  
> >  static const struct ethtool_ops mvpp2_eth_tool_ops = {
> > -- 
> > 2.26.2
> >