[PATCH net-next v6 12/14] net: lan966x: add PCIe FDMA XDP support
Daniel Machon
daniel.machon at microchip.com
Wed Sep 9 06:00:14 PDT 2026
Add XDP support for the PCIe FDMA path. The implementation operates on
contiguous ATU-mapped buffers with memcpy-based XDP_TX, unlike the
platform path which uses page_pool.
XDP sees the frame with IFH and FCS stripped. These are removed in
lan966x_fdma_pci_rx_check_frame() before the BPF program runs, because
after the program returns the driver cannot tell whether the tail
region was modified. The skb_pull/skb_trim previously done in
lan966x_fdma_pci_rx_get_frame() are removed for the same reason; the
frame pointer and length are pre-computed by rx_check_frame() and
passed through rx_get_frame() and lan966x_xdp_pci_run() to the caller.
lan966x_fdma_pci_xmit_xdpf() handles XDP_TX: it rebuilds a fresh IFH
in the TX slot, copies the post-XDP frame after it, and lets HW insert
a new FCS.
lan966x_xdp_setup() is extended so the PCIe path skips the page_pool
reload that the platform path needs.
Only XDP_ACT_BASIC is supported.
Tested-by: Herve Codina <herve.codina at bootlin.com>
Signed-off-by: Daniel Machon <daniel.machon at microchip.com>
---
.../ethernet/microchip/lan966x/lan966x_fdma_pci.c | 166 ++++++++++++++++++---
.../net/ethernet/microchip/lan966x/lan966x_main.c | 12 +-
.../net/ethernet/microchip/lan966x/lan966x_xdp.c | 12 +-
3 files changed, 159 insertions(+), 31 deletions(-)
diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma_pci.c b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma_pci.c
index 6cabbb8b47f2..02c021617a3e 100644
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma_pci.c
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma_pci.c
@@ -1,5 +1,6 @@
// SPDX-License-Identifier: GPL-2.0+
+#include <linux/bpf_trace.h>
#include <linux/mmzone.h>
#include "fdma_api.h"
@@ -126,7 +127,123 @@ static bool lan966x_fdma_pci_rx_size_fits(struct fdma *fdma, u32 blockl)
blockl <= fdma->db_size - XDP_PACKET_HEADROOM;
}
-static int lan966x_fdma_pci_rx_check_frame(struct lan966x_rx *rx, u64 *src_port)
+static int lan966x_fdma_pci_xmit_xdpf(struct lan966x_port *port,
+ void *ptr, u32 len)
+{
+ struct lan966x *lan966x = port->lan966x;
+ struct lan966x_tx *tx = &lan966x->tx;
+ struct fdma *fdma = &tx->fdma;
+ int next_to_use, ret = 0;
+ void *virt_addr;
+
+ spin_lock(&lan966x->tx_lock);
+
+ next_to_use = lan966x_fdma_pci_get_next_dcb(fdma);
+
+ if (next_to_use < 0) {
+ netif_stop_queue(port->dev);
+ port->dev->stats.tx_dropped++;
+ ret = NETDEV_TX_BUSY;
+ goto out;
+ }
+
+ /* Only the upper bound is enforced: XDP owns the frame contents and
+ * length, so a program that shrinks below ETH_ZLEN gets what it asked
+ * for.
+ */
+ if (!lan966x_fdma_pci_tx_size_fits(fdma, len)) {
+ port->dev->stats.tx_dropped++;
+ ret = -EINVAL;
+ goto out;
+ }
+
+ /* virt_addr points to the IFH. */
+ virt_addr = fdma_dataptr_virt_addr_contiguous(fdma, next_to_use, 0);
+
+ /* Construct a fresh IFH. */
+ memset(virt_addr, 0, IFH_LEN_BYTES);
+ lan966x_ifh_set_bypass(virt_addr, 1);
+ lan966x_ifh_set_port(virt_addr, BIT_ULL(port->chip_port));
+
+ /* Copy the (post-XDP) frame after the IFH. */
+ memcpy(virt_addr + IFH_LEN_BYTES, ptr, len);
+
+ /* Order frame write before DCB status write below. */
+ dma_wmb();
+
+ /* Reserve ETH_FCS_LEN for the HW-inserted FCS (len is FCS-stripped). */
+ fdma_dcb_add(fdma,
+ next_to_use,
+ 0,
+ FDMA_DCB_STATUS_INTR |
+ FDMA_DCB_STATUS_SOF |
+ FDMA_DCB_STATUS_EOF |
+ FDMA_DCB_STATUS_BLOCKO(0) |
+ FDMA_DCB_STATUS_BLOCKL(IFH_LEN_BYTES + len + ETH_FCS_LEN));
+
+ /* Start the transmission. */
+ lan966x_fdma_tx_start(tx);
+
+ port->dev->stats.tx_bytes += len;
+ port->dev->stats.tx_packets++;
+
+out:
+ spin_unlock(&lan966x->tx_lock);
+
+ return ret;
+}
+
+static int lan966x_xdp_pci_run(struct lan966x_port *port, void *data,
+ u32 data_len, void **xdp_data, u32 *xdp_len)
+{
+ /* Read once so the NULL check and bpf_prog_run_xdp() see the same
+ * pointer.
+ */
+ struct bpf_prog *xdp_prog = READ_ONCE(port->xdp_prog);
+ struct lan966x *lan966x = port->lan966x;
+ struct fdma *fdma = &lan966x->rx.fdma;
+ struct xdp_buff xdp;
+ u32 act;
+
+ if (!xdp_prog)
+ return FDMA_PASS;
+
+ xdp_init_buff(&xdp, fdma->db_size, &port->xdp_rxq);
+
+ /* hard_start is set to slot start (virt_addr is XDP_PACKET_HEADROOM
+ * into the slot). Headroom includes the IFH; BPF may grow into it
+ * via adjust_head. IFH is rebuilt on XDP_TX and unread on XDP_PASS.
+ */
+ xdp_prepare_buff(&xdp,
+ data - XDP_PACKET_HEADROOM,
+ XDP_PACKET_HEADROOM + IFH_LEN_BYTES,
+ data_len,
+ false);
+
+ act = bpf_prog_run_xdp(xdp_prog, &xdp);
+
+ *xdp_data = xdp.data;
+ *xdp_len = xdp.data_end - xdp.data;
+
+ switch (act) {
+ case XDP_PASS:
+ return FDMA_PASS;
+ case XDP_TX:
+ return lan966x_fdma_pci_xmit_xdpf(port, *xdp_data, *xdp_len) ?
+ FDMA_DROP : FDMA_TX;
+ default:
+ bpf_warn_invalid_xdp_action(port->dev, xdp_prog, act);
+ fallthrough;
+ case XDP_ABORTED:
+ trace_xdp_exception(port->dev, xdp_prog, act);
+ fallthrough;
+ case XDP_DROP:
+ return FDMA_DROP;
+ }
+}
+
+static int lan966x_fdma_pci_rx_check_frame(struct lan966x_rx *rx, u64 *src_port,
+ void **data, u32 *data_len)
{
struct lan966x *lan966x = rx->lan966x;
struct fdma *fdma = &rx->fdma;
@@ -158,38 +275,33 @@ static int lan966x_fdma_pci_rx_check_frame(struct lan966x_rx *rx, u64 *src_port)
if (!lan966x_fdma_pci_rx_size_fits(fdma, blockl))
return FDMA_ERROR;
- return FDMA_PASS;
+ /* Present the Ethernet frame (no IFH, no FCS). HW re-inserts the
+ * FCS on TX; see lan966x_fdma_pci_xmit_xdpf(). May be overridden
+ * by XDP. The FCS strip is unconditional because NETIF_F_RXFCS
+ * is not advertised in hw_features.
+ */
+ *data = virt_addr + IFH_LEN_BYTES;
+ *data_len = blockl - IFH_LEN_BYTES - ETH_FCS_LEN;
+
+ return lan966x_xdp_pci_run(port, virt_addr, *data_len, data, data_len);
}
static struct sk_buff *lan966x_fdma_pci_rx_get_frame(struct lan966x_rx *rx,
- u64 src_port)
+ u64 src_port, void *data,
+ u32 data_len)
{
struct lan966x *lan966x = rx->lan966x;
- struct fdma *fdma = &rx->fdma;
struct sk_buff *skb;
- struct fdma_db *db;
- u32 data_len;
-
- /* Get the received frame and create an SKB for it. */
- db = fdma_db_next_get(fdma);
- data_len = FDMA_DCB_STATUS_BLOCKL(db->status);
skb = napi_alloc_skb(&lan966x->napi, data_len);
if (unlikely(!skb))
return NULL;
- memcpy(skb->data,
- fdma_dataptr_virt_addr_contiguous(fdma,
- fdma->dcb_index,
- fdma->db_index),
- data_len);
+ memcpy(skb->data, data, data_len);
skb_put(skb, data_len);
skb->dev = lan966x->ports[src_port]->dev;
- skb_pull(skb, IFH_LEN_BYTES);
-
- skb_trim(skb, skb->len - ETH_FCS_LEN);
skb->protocol = eth_type_trans(skb, skb->dev);
@@ -277,6 +389,8 @@ static int lan966x_fdma_pci_napi_poll(struct napi_struct *napi, int weight)
struct sk_buff *skb;
int counter = 0;
u64 src_port;
+ u32 data_len;
+ void *data;
/* Wake any stopped TX queues if a TX DCB is available. */
spin_lock(&lan966x->tx_lock);
@@ -293,7 +407,10 @@ static int lan966x_fdma_pci_napi_poll(struct napi_struct *napi, int weight)
/* Order DONE read before DCB/frame reads below. */
dma_rmb();
counter++;
- switch (lan966x_fdma_pci_rx_check_frame(rx, &src_port)) {
+ switch (lan966x_fdma_pci_rx_check_frame(rx,
+ &src_port,
+ &data,
+ &data_len)) {
case FDMA_PASS:
break;
case FDMA_ERROR:
@@ -302,8 +419,17 @@ static int lan966x_fdma_pci_napi_poll(struct napi_struct *napi, int weight)
*/
fdma_dcb_advance(fdma);
continue;
+ case FDMA_TX:
+ fdma_dcb_advance(fdma);
+ continue;
+ case FDMA_DROP:
+ fdma_dcb_advance(fdma);
+ continue;
}
- skb = lan966x_fdma_pci_rx_get_frame(rx, src_port);
+ skb = lan966x_fdma_pci_rx_get_frame(rx,
+ src_port,
+ data,
+ data_len);
fdma_dcb_advance(fdma);
if (!skb) {
lan966x->ports[src_port]->dev->stats.rx_dropped++;
diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_main.c b/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
index e089c08b9c37..9ada497767c6 100644
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
@@ -874,11 +874,13 @@ static int lan966x_probe_port(struct lan966x *lan966x, u32 p,
port->phylink = phylink;
- /* XDP is not supported on the PCIe FDMA path. */
- if (lan966x->fdma && !lan966x_is_pci(lan966x))
- dev->xdp_features = NETDEV_XDP_ACT_BASIC |
- NETDEV_XDP_ACT_REDIRECT |
- NETDEV_XDP_ACT_NDO_XMIT;
+ if (lan966x->fdma) {
+ dev->xdp_features = NETDEV_XDP_ACT_BASIC;
+
+ if (!lan966x_is_pci(lan966x))
+ dev->xdp_features |= NETDEV_XDP_ACT_REDIRECT |
+ NETDEV_XDP_ACT_NDO_XMIT;
+ }
err = register_netdev(dev);
if (err) {
diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_xdp.c b/drivers/net/ethernet/microchip/lan966x/lan966x_xdp.c
index e63634887f64..b98426afc785 100644
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_xdp.c
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_xdp.c
@@ -20,16 +20,16 @@ static int lan966x_xdp_setup(struct net_device *dev, struct netdev_bpf *xdp)
return -EOPNOTSUPP;
}
- if (lan966x_is_pci(lan966x)) {
- NL_SET_ERR_MSG_MOD(xdp->extack,
- "XDP is not supported on the PCIe FDMA path");
- return -EOPNOTSUPP;
- }
-
old_xdp = lan966x_xdp_present(lan966x);
old_prog = xchg(&port->xdp_prog, xdp->prog);
new_xdp = lan966x_xdp_present(lan966x);
+ /* PCIe FDMA uses contiguous buffers, so no page_pool reload
+ * is needed.
+ */
+ if (lan966x_is_pci(lan966x))
+ goto out;
+
if (old_xdp == new_xdp)
goto out;
--
2.34.1
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