Hi dasanfreedom,
Would you please upload your code let us have a review ?
Or you can refer to nvidia/drivers/pci/endpoint/functions/pci-epf-tegra-vnet.c which transfer skb by PCIe DMA
function:
static netdev_tx_t tvnet_ep_start_xmit(struct sk_buff *skb,
struct net_device *ndev)