[PATCH net-next v6 3/7] net: bcmgenet: add basic XDP support (PASS/DROP)

Nicolai Buchwitz
2026-04-06T08:36:37Z

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 | 139 +++++++++++++++---
.../net/ethernet/broadcom/genet/bcmgenet.h | 4 +
2 files changed, 123 insertions(+), 20 deletions(-)

diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
index 6b66a95c2f08..187fa11ad5c2 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)
+{
+ 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 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);
@@ -2325,7 +2377,7 @@ static unsigned int bcmgenet_desc_rx(struct bcmgenet_rx_ring *ring,
struct status_64 *status;
struct page *rx_page;
unsigned int rx_off;
- __be16 rx_csum;
+ __be16 rx_csum = 0;
void *hard_start;

cb = &priv->rx_cbs[ring->read_ptr];
@@ -2403,30 +2455,44 @@ 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);
-
- /* Reserve the RSB + pad, then set the data length */
- skb_reserve(skb, GENET_RSB_PAD);
- __skb_put(skb, len - GENET_RSB_PAD);
+ {
+ 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;
+
+ /* Save rx_csum before XDP runs - an XDP program
+ * could overwrite the RSB via bpf_xdp_adjust_head.
+ */
+ if (dev->features & NETIF_F_RXCSUM)
+ rx_csum = (__force __be16)(status->rx_csum
+ & 0xffff);
+
+ xdp_init_buff(&xdp, PAGE_SIZE, &ring->xdp_rxq);
+ xdp_prepare_buff(&xdp, page_address(rx_page),
+ GENET_RX_HEADROOM, pkt_len, true);
+
+ if (xdp_prog) {
+ xdp_act = bcmgenet_run_xdp(ring, xdp_prog,
+ &xdp, rx_page);
+ if (xdp_act != XDP_PASS)
+ goto next;
+ }

- if (priv->crc_fwd_en) {
- skb_trim(skb, skb->len - ETH_FCS_LEN);
+ skb = bcmgenet_xdp_build_skb(ring, &xdp);
+ if (unlikely(!skb)) {
+ BCMGENET_STATS64_INC(stats, dropped);
+ page_pool_put_full_page(ring->page_pool,
+ rx_page, true);
+ goto next;
+ }
}

/* Set up checksum offload */
if (dev->features & NETIF_F_RXCSUM) {
- rx_csum = (__force __be16)(status->rx_csum & 0xffff);
if (rx_csum) {
skb->csum = (__force __wsum)ntohs(rx_csum);
skb->ip_summed = CHECKSUM_COMPLETE;
@@ -3744,6 +3810,37 @@ 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,
@@ -3755,6 +3852,7 @@ 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 */
@@ -4057,6 +4155,7 @@ 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)
--
2.51.0