Re: [PATCH net-next v3 5/6] net: bcmgenet: add XDP_REDIRECT and ndo_xdp_xmit support

[Justin Chen <justin.chen@broadcom.com>]

On 3/19/26 4:53 AM, Nicolai Buchwitz wrote:
> Add XDP_REDIRECT support and implement ndo_xdp_xmit for receiving
> redirected frames from other devices.
> 
> XDP_REDIRECT calls xdp_do_redirect() in the RX path with
> xdp_do_flush() once per NAPI poll cycle. ndo_xdp_xmit batches frames
> into ring 16 under a single spinlock acquisition.
> 
> Advertise NETDEV_XDP_ACT_REDIRECT and NETDEV_XDP_ACT_NDO_XMIT in
> xdp_features.
> 
> Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>
> ---
>   .../net/ethernet/broadcom/genet/bcmgenet.c    | 98 +++++++++++++++----
>   1 file changed, 80 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> index 54df1694f1cd..a5ad25ccb148 100644
> --- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> +++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> @@ -2320,23 +2320,23 @@ static struct sk_buff *bcmgenet_xdp_build_skb(struct bcmgenet_rx_ring *ring,
>   	return skb;
>   }
>   
> +/* Submit a single XDP frame to the TX ring. Caller must hold ring->lock.
> + * Returns true on success. Does not ring the doorbell - caller must
> + * write TDMA_PROD_INDEX after batching.
> + */
>   static bool
>   bcmgenet_xdp_xmit_frame(struct bcmgenet_priv *priv,
> +			struct bcmgenet_tx_ring *ring,
>   			struct xdp_frame *xdpf, bool dma_map)
>   {
> -	struct bcmgenet_tx_ring *ring = &priv->tx_rings[DESC_INDEX];
>   	struct device *kdev = &priv->pdev->dev;
>   	struct enet_cb *tx_cb_ptr;
>   	dma_addr_t mapping;
>   	unsigned int dma_len;
>   	u32 len_stat;
>   
> -	spin_lock(&ring->lock);
> -
> -	if (ring->free_bds < 1) {
> -		spin_unlock(&ring->lock);
> +	if (ring->free_bds < 1)
>   		return false;
> -	}
>   
>   	tx_cb_ptr = bcmgenet_get_txcb(priv, ring);
>   
> @@ -2350,7 +2350,6 @@ bcmgenet_xdp_xmit_frame(struct bcmgenet_priv *priv,
>   		 */
>   		if (unlikely(xdpf->headroom < sizeof(struct status_64))) {
>   			bcmgenet_put_txcb(priv, ring);
> -			spin_unlock(&ring->lock);
>   			return false;
>   		}
>   
> @@ -2364,7 +2363,6 @@ bcmgenet_xdp_xmit_frame(struct bcmgenet_priv *priv,
>   			tx_cb_ptr->skb = NULL;
>   			tx_cb_ptr->xdpf = NULL;
>   			bcmgenet_put_txcb(priv, ring);
> -			spin_unlock(&ring->lock);
>   			return false;
>   		}
>   	} else {
> @@ -2396,12 +2394,15 @@ bcmgenet_xdp_xmit_frame(struct bcmgenet_priv *priv,
>   	ring->prod_index++;
>   	ring->prod_index &= DMA_P_INDEX_MASK;
>   
> +	return true;
> +}
> +
> +static void

Perfer to remove newline.

> +bcmgenet_xdp_ring_doorbell(struct bcmgenet_priv *priv,
> +			   struct bcmgenet_tx_ring *ring)
> +{
>   	bcmgenet_tdma_ring_writel(priv, ring->index, ring->prod_index,
>   				  TDMA_PROD_INDEX);
> -
> -	spin_unlock(&ring->lock);
> -
> -	return true;
>   }
>   
>   static unsigned int
> @@ -2417,7 +2418,11 @@ bcmgenet_run_xdp(struct bcmgenet_rx_ring *ring, struct bpf_prog *prog,
>   	switch (act) {
>   	case XDP_PASS:
>   		return XDP_PASS;
> -	case XDP_TX:
> +	case XDP_TX: {
> +		struct bcmgenet_tx_ring *tx_ring;
> +
> +		tx_ring = &priv->tx_rings[DESC_INDEX];
> +
>   		/* Prepend a zeroed TSB (Transmit Status Block).  The GENET
>   		 * MAC has TBUF_64B_EN set globally, so hardware expects every
>   		 * TX buffer to begin with a 64-byte struct status_64.  Back
> @@ -2429,14 +2434,26 @@ bcmgenet_run_xdp(struct bcmgenet_rx_ring *ring, struct bpf_prog *prog,
>   		memset(xdp->data, 0, sizeof(struct status_64));
>   
>   		xdpf = xdp_convert_buff_to_frame(xdp);
> -		if (unlikely(!xdpf) ||
> -		    unlikely(!bcmgenet_xdp_xmit_frame(priv, xdpf, false))) {
> -			page_pool_put_full_page(ring->page_pool, rx_page,
> -						true);
> +		if (unlikely(!xdpf))
> +			goto drop_page;
> +
> +		spin_lock(&tx_ring->lock);
> +		if (unlikely(!bcmgenet_xdp_xmit_frame(priv, tx_ring,
> +						      xdpf, false))) {
> +			spin_unlock(&tx_ring->lock);
> +			xdp_return_frame_rx_napi(xdpf);
>   			return XDP_DROP;
>   		}
> +		bcmgenet_xdp_ring_doorbell(priv, tx_ring);
> +		spin_unlock(&tx_ring->lock);
>   		return XDP_TX;
> +	}

Don't think we need this extra curly bracket here.

> +	case XDP_REDIRECT:
> +		if (unlikely(xdp_do_redirect(priv->dev, xdp, prog)))
> +			goto drop_page;
> +		return XDP_REDIRECT;
>   	case XDP_DROP:
> +drop_page:

Not a big fan of jumping like this within switch statements.

>   		page_pool_put_full_page(ring->page_pool, rx_page, true);
>   		return XDP_DROP;
>   	default:
> @@ -2459,6 +2476,7 @@ static unsigned int bcmgenet_desc_rx(struct bcmgenet_rx_ring *ring,
>   	struct bcmgenet_priv *priv = ring->priv;
>   	struct net_device *dev = priv->dev;
>   	struct bpf_prog *xdp_prog;
> +	bool xdp_flush = false;
>   	struct enet_cb *cb;
>   	struct sk_buff *skb;
>   	u32 dma_length_status;
> @@ -2597,6 +2615,8 @@ static unsigned int bcmgenet_desc_rx(struct bcmgenet_rx_ring *ring,
>   
>   			xdp_act = bcmgenet_run_xdp(ring, xdp_prog, &xdp,
>   						   rx_page);
> +			if (xdp_act == XDP_REDIRECT)
> +				xdp_flush = true;
>   			if (xdp_act != XDP_PASS)
>   				goto next;
>   
> @@ -2670,6 +2690,9 @@ static unsigned int bcmgenet_desc_rx(struct bcmgenet_rx_ring *ring,
>   		bcmgenet_rdma_ring_writel(priv, ring->index, ring->c_index, RDMA_CONS_INDEX);
>   	}
>   
> +	if (xdp_flush)
> +		xdp_do_flush();
> +
>   	ring->dim.bytes = bytes_processed;
>   	ring->dim.packets = rxpktprocessed;
>   
> @@ -3995,10 +4018,16 @@ static int bcmgenet_xdp_setup(struct net_device *dev,
>   		return -EOPNOTSUPP;
>   	}
>   
> +	if (!prog)
> +		xdp_features_clear_redirect_target(dev);
> +
>   	old_prog = xchg(&priv->xdp_prog, prog);
>   	if (old_prog)
>   		bpf_prog_put(old_prog);
>   
> +	if (prog)
> +		xdp_features_set_redirect_target(dev, false);
> +
>   	return 0;
>   }
>   
> @@ -4012,6 +4041,37 @@ static int bcmgenet_xdp(struct net_device *dev, struct netdev_bpf *xdp)
>   	}
>   }
>   
> +static int

Same as before

> +bcmgenet_xdp_xmit(struct net_device *dev, int num_frames,
> +		  struct xdp_frame **frames, u32 flags)
> +{
> +	struct bcmgenet_priv *priv = netdev_priv(dev);
> +	struct bcmgenet_tx_ring *ring = &priv->tx_rings[DESC_INDEX];
> +	int sent = 0;
> +	int i;
> +
> +	if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK))
> +		return -EINVAL;
> +
> +	if (unlikely(!netif_running(dev)))
> +		return -ENETDOWN;
> +
> +	spin_lock(&ring->lock);
> +
> +	for (i = 0; i < num_frames; i++) {
> +		if (!bcmgenet_xdp_xmit_frame(priv, ring, frames[i], true))
> +			break;
> +		sent++;
> +	}
> +
> +	if (sent)
> +		bcmgenet_xdp_ring_doorbell(priv, ring);
> +
> +	spin_unlock(&ring->lock);
> +
> +	return sent;
> +}
> +
>   static const struct net_device_ops bcmgenet_netdev_ops = {
>   	.ndo_open		= bcmgenet_open,
>   	.ndo_stop		= bcmgenet_close,
> @@ -4024,6 +4084,7 @@ static const struct net_device_ops bcmgenet_netdev_ops = {
>   	.ndo_get_stats64	= bcmgenet_get_stats64,
>   	.ndo_change_carrier	= bcmgenet_change_carrier,
>   	.ndo_bpf		= bcmgenet_xdp,
> +	.ndo_xdp_xmit		= bcmgenet_xdp_xmit,
>   };
>   
>   /* GENET hardware parameters/characteristics */
> @@ -4326,7 +4387,8 @@ static int bcmgenet_probe(struct platform_device *pdev)
>   			 NETIF_F_RXCSUM;
>   	dev->hw_features |= dev->features;
>   	dev->vlan_features |= dev->features;
> -	dev->xdp_features = NETDEV_XDP_ACT_BASIC;
> +	dev->xdp_features = NETDEV_XDP_ACT_BASIC | NETDEV_XDP_ACT_REDIRECT |
> +			    NETDEV_XDP_ACT_NDO_XMIT;
>   
>   	netdev_sw_irq_coalesce_default_on(dev);
>