What is the event that XDP socket is attached to?

I am developing a kernel module that registers to the receive handler like this:

rx_handler_result_t rxhPacketIn(struct sk_buff **ppkt)

However, when I tried to use this kernel module program with XDP program from XDP-tutorial 1, the kernel module was not involved at all, even when I tried to only pass the packets in the XDP kernel program (return XDP_PASS). So my question is, how XDP kernel program is attached to the kernel, and does it has higher priority than the kernel module registered as a rx_handler ?