net: fec: add fec_enet_rx_queue_xdp() for XDP path

net: fec: add fec_enet_rx_queue_xdp() for XDP path

Currently, the processing of XDP path packets and protocol stack packets
are both mixed in fec_enet_rx_queue(), which makes the logic somewhat
confusing and debugging more difficult. Furthermore, some logic is not
needed by each other. Such as the kernel path does not need to call
xdp_init_buff(), XDP path does not support swap_buffer(), because
fec_enet_bpf() returns "-EOPNOTSUPP" for those platforms which need
swap_buffer()), and so on. This prevents XDP from achieving its maximum
performance. Therefore, XDP path packets processing has been separated
from fec_enet_rx_queue() by adding the fec_enet_rx_queue_xdp() function
to optimize XDP path logic and improve XDP performance.

The XDP performance on the iMX93 platform was compared before and after
applying this patch. Detailed results are as follows and we can see the
performance has been improved.

Env: i.MX93, packet size 64 bytes including FCS, only single core and RX
BD ring are used to receive packets, flow-control is off.

Before the patch is applied:
xdp-bench tx eth0
Summary                   396,868 rx/s                  0 err,drop/s
Summary                   396,024 rx/s                  0 err,drop/s

xdp-bench drop eth0
Summary                   684,781 rx/s                  0 err/s
Summary                   675,746 rx/s                  0 err/s

xdp-bench pass eth0
Summary                   208,552 rx/s                  0 err,drop/s
Summary                   208,654 rx/s                  0 err,drop/s

xdp-bench redirect eth0 eth0
eth0->eth0                311,210 rx/s                  0 err,drop/s      311,208 xmit/s
eth0->eth0                310,808 rx/s                  0 err,drop/s      310,809 xmit/s

After the patch is applied:
xdp-bench tx eth0
Summary                   409,975 rx/s                  0 err,drop/s
Summary                   411,073 rx/s                  0 err,drop/s

xdp-bench drop eth0
Summary                   700,681 rx/s                  0 err/s
Summary                   698,102 rx/s                  0 err/s

xdp-bench pass eth0
Summary                   211,356 rx/s                  0 err,drop/s
Summary                   210,629 rx/s                  0 err,drop/s

xdp-bench redirect eth0 eth0
eth0->eth0                320,351 rx/s                  0 err,drop/s      320,348 xmit/s
eth0->eth0                318,988 rx/s                  0 err,drop/s      318,988 xmit/s

Signed-off-by: Wei Fang <wei.fang@nxp.com>
Link: https://patch.msgid.link/20260205085742.2685134-7-wei.fang@nxp.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>