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

Justin Chen
2026-03-19T21:34:17Z

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);
>