Re: [PATCH net-next v3 3/6] net: bcmgenet: add basic XDP support (PASS/DROP)

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

On 3/19/26 4:53 AM, Nicolai Buchwitz wrote:
> Add XDP program attachment via ndo_bpf and execute XDP programs in the
> RX path. XDP_PASS builds an SKB from the xdp_buff (handling
> xdp_adjust_head/tail), XDP_DROP returns the page to page_pool without
> SKB allocation.
> 
> XDP_TX and XDP_REDIRECT are not yet supported and return XDP_ABORTED.
> 
> Advertise NETDEV_XDP_ACT_BASIC in xdp_features.
> 
> Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>
> ---
>   .../net/ethernet/broadcom/genet/bcmgenet.c    | 147 +++++++++++++++---
>   .../net/ethernet/broadcom/genet/bcmgenet.h    |   4 +
>   2 files changed, 133 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> index 6e610e73e12f..e8f90d6b16a2 100644
> --- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> +++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> @@ -35,6 +35,8 @@
>   #include <linux/ip.h>
>   #include <linux/ipv6.h>
>   #include <linux/phy.h>
> +#include <linux/bpf_trace.h>
> +#include <linux/filter.h>
>   
>   #include <linux/unaligned.h>
>   
> @@ -2274,6 +2276,53 @@ static int bcmgenet_rx_refill(struct bcmgenet_rx_ring *ring,
>   	return 0;
>   }
>   
> +static struct sk_buff *bcmgenet_xdp_build_skb(struct bcmgenet_rx_ring *ring,
> +					      struct xdp_buff *xdp,
> +					      struct page *rx_page)
> +{
> +	unsigned int metasize;
> +	struct sk_buff *skb;
> +
> +	skb = napi_build_skb(xdp->data_hard_start, PAGE_SIZE);
> +	if (unlikely(!skb))
> +		return NULL;
> +
> +	skb_mark_for_recycle(skb);
> +
> +	metasize = xdp->data - xdp->data_meta;
> +	skb_reserve(skb, xdp->data - xdp->data_hard_start);
> +	__skb_put(skb, xdp->data_end - xdp->data);
> +
> +	if (metasize)
> +		skb_metadata_set(skb, metasize);
> +
> +	return skb;
> +}
> +
> +static unsigned int

Perfer to not have a newline here. To match the formatting of the rest 
of the driver.

Thanks,
Justin

> +bcmgenet_run_xdp(struct bcmgenet_rx_ring *ring, struct bpf_prog *prog,
> +		 struct xdp_buff *xdp, struct page *rx_page)
> +{
> +	unsigned int act;
> +
> +	act = bpf_prog_run_xdp(prog, xdp);
> +
> +	switch (act) {
> +	case XDP_PASS:
> +		return XDP_PASS;
> +	case XDP_DROP:
> +		page_pool_put_full_page(ring->page_pool, rx_page, true);
> +		return XDP_DROP;
> +	default:
> +		bpf_warn_invalid_xdp_action(ring->priv->dev, prog, act);
> +		fallthrough;
> +	case XDP_ABORTED:
> +		trace_xdp_exception(ring->priv->dev, prog, act);
> +		page_pool_put_full_page(ring->page_pool, rx_page, true);
> +		return XDP_ABORTED;
> +	}
> +}
> +
>   /* bcmgenet_desc_rx - descriptor based rx process.
>    * this could be called from bottom half, or from NAPI polling method.
>    */
> @@ -2283,6 +2332,7 @@ static unsigned int bcmgenet_desc_rx(struct bcmgenet_rx_ring *ring,
>   	struct bcmgenet_rx_stats64 *stats = &ring->stats64;
>   	struct bcmgenet_priv *priv = ring->priv;
>   	struct net_device *dev = priv->dev;
> +	struct bpf_prog *xdp_prog;
>   	struct enet_cb *cb;
>   	struct sk_buff *skb;
>   	u32 dma_length_status;
> @@ -2293,6 +2343,8 @@ static unsigned int bcmgenet_desc_rx(struct bcmgenet_rx_ring *ring,
>   	unsigned int p_index, mask;
>   	unsigned int discards;
>   
> +	xdp_prog = READ_ONCE(priv->xdp_prog);
> +
>   	/* Clear status before servicing to reduce spurious interrupts */
>   	mask = 1 << (UMAC_IRQ1_RX_INTR_SHIFT + ring->index);
>   	bcmgenet_intrl2_1_writel(priv, mask, INTRL2_CPU_CLEAR);
> @@ -2403,26 +2455,52 @@ static unsigned int bcmgenet_desc_rx(struct bcmgenet_rx_ring *ring,
>   			goto next;
>   		} /* error packet */
>   
> -		/* Build SKB from the page - data starts at hard_start,
> -		 * frame begins after RSB(64) + pad(2) = 66 bytes.
> -		 */
> -		skb = napi_build_skb(hard_start, PAGE_SIZE - GENET_XDP_HEADROOM);
> -		if (unlikely(!skb)) {
> -			BCMGENET_STATS64_INC(stats, dropped);
> -			page_pool_put_full_page(ring->page_pool, rx_page,
> -						true);
> -			goto next;
> -		}
> -
> -		skb_mark_for_recycle(skb);
> +		/* XDP: frame data starts after RSB + pad */
> +		if (xdp_prog) {
> +			struct xdp_buff xdp;
> +			unsigned int xdp_act;
> +			int pkt_len;
> +
> +			pkt_len = len - GENET_RSB_PAD;
> +			if (priv->crc_fwd_en)
> +				pkt_len -= ETH_FCS_LEN;
> +
> +			xdp_init_buff(&xdp, PAGE_SIZE, &ring->xdp_rxq);
> +			xdp_prepare_buff(&xdp, page_address(rx_page),
> +					 GENET_RX_HEADROOM, pkt_len, true);
> +
> +			xdp_act = bcmgenet_run_xdp(ring, xdp_prog, &xdp,
> +						   rx_page);
> +			if (xdp_act != XDP_PASS)
> +				goto next;
> +
> +			/* XDP_PASS: build SKB from (possibly modified) xdp */
> +			skb = bcmgenet_xdp_build_skb(ring, &xdp, rx_page);
> +			if (unlikely(!skb)) {
> +				BCMGENET_STATS64_INC(stats, dropped);
> +				page_pool_put_full_page(ring->page_pool,
> +							rx_page, true);
> +				goto next;
> +			}
> +		} else {
> +			/* Build SKB from the page - data starts at
> +			 * hard_start, frame begins after RSB(64) + pad(2).
> +			 */
> +			skb = napi_build_skb(hard_start,
> +					     PAGE_SIZE - GENET_XDP_HEADROOM);
> +			if (unlikely(!skb)) {
> +				BCMGENET_STATS64_INC(stats, dropped);
> +				page_pool_put_full_page(ring->page_pool,
> +							rx_page, true);
> +				goto next;
> +			}
>   
> -		/* Reserve the RSB + pad, then set the data length */
> -		skb_reserve(skb, GENET_RSB_PAD);
> -		__skb_put(skb, len - GENET_RSB_PAD);
> +			skb_mark_for_recycle(skb);
> +			skb_reserve(skb, GENET_RSB_PAD);
> +			__skb_put(skb, len - GENET_RSB_PAD);
>   
> -		if (priv->crc_fwd_en) {
> -			skb_trim(skb, skb->len - ETH_FCS_LEN);
> -			len -= ETH_FCS_LEN;
> +			if (priv->crc_fwd_en)
> +				skb_trim(skb, skb->len - ETH_FCS_LEN);
>   		}
>   
>   		/* Set up checksum offload */
> @@ -3743,6 +3821,37 @@ static int bcmgenet_change_carrier(struct net_device *dev, bool new_carrier)
>   	return 0;
>   }
>   
> +static int bcmgenet_xdp_setup(struct net_device *dev,
> +			      struct netdev_bpf *xdp)
> +{
> +	struct bcmgenet_priv *priv = netdev_priv(dev);
> +	struct bpf_prog *old_prog;
> +	struct bpf_prog *prog = xdp->prog;
> +
> +	if (prog && dev->mtu > PAGE_SIZE - GENET_RX_HEADROOM -
> +	    SKB_DATA_ALIGN(sizeof(struct skb_shared_info))) {
> +		NL_SET_ERR_MSG_MOD(xdp->extack,
> +				   "MTU too large for single-page XDP buffer");
> +		return -EOPNOTSUPP;
> +	}
> +
> +	old_prog = xchg(&priv->xdp_prog, prog);
> +	if (old_prog)
> +		bpf_prog_put(old_prog);
> +
> +	return 0;
> +}
> +
> +static int bcmgenet_xdp(struct net_device *dev, struct netdev_bpf *xdp)
> +{
> +	switch (xdp->command) {
> +	case XDP_SETUP_PROG:
> +		return bcmgenet_xdp_setup(dev, xdp);
> +	default:
> +		return -EOPNOTSUPP;
> +	}
> +}
> +
>   static const struct net_device_ops bcmgenet_netdev_ops = {
>   	.ndo_open		= bcmgenet_open,
>   	.ndo_stop		= bcmgenet_close,
> @@ -3754,6 +3863,7 @@ static const struct net_device_ops bcmgenet_netdev_ops = {
>   	.ndo_set_features	= bcmgenet_set_features,
>   	.ndo_get_stats64	= bcmgenet_get_stats64,
>   	.ndo_change_carrier	= bcmgenet_change_carrier,
> +	.ndo_bpf		= bcmgenet_xdp,
>   };
>   
>   /* GENET hardware parameters/characteristics */
> @@ -4056,6 +4166,7 @@ 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;
>   
>   	netdev_sw_irq_coalesce_default_on(dev);
>   
> diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.h b/drivers/net/ethernet/broadcom/genet/bcmgenet.h
> index 82a6d29f481d..1459473ac1b0 100644
> --- a/drivers/net/ethernet/broadcom/genet/bcmgenet.h
> +++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.h
> @@ -16,6 +16,7 @@
>   #include <linux/dim.h>
>   #include <linux/ethtool.h>
>   #include <net/page_pool/helpers.h>
> +#include <linux/bpf.h>
>   #include <net/xdp.h>
>   
>   #include "../unimac.h"
> @@ -671,6 +672,9 @@ struct bcmgenet_priv {
>   	u8 sopass[SOPASS_MAX];
>   
>   	struct bcmgenet_mib_counters mib;
> +
> +	/* XDP */
> +	struct bpf_prog *xdp_prog;
>   };
>   
>   static inline bool bcmgenet_has_40bits(struct bcmgenet_priv *priv)