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

Justin Chen
2026-03-19T21:23:07Z

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)