On Wed, 31 Mar 2021 23:41:34 +0800 Ong Boon Leong wrote:
> This patch adds support for XDP_TX action which enables XDP program to
> transmit back received frames.
>
> This patch has been tested with the "xdp2" app located in samples/bpf
> dir. The DUT receives burst traffic packet generated using pktgen script
> 'pktgen_sample03_burst_single_flow.sh'.
>
> v3: Added 'nq->trans_start = jiffies' to avoid TX time-out as we are
> sharing TX queue between slow path and XDP. Thanks to Jakub Kicinski
> for pointing out.
>
> Signed-off-by: Ong Boon Leong <boon.leong.ong@xxxxxxxxx>
> +static int stmmac_xdp_xmit_back(struct stmmac_priv *priv,
> + struct xdp_buff *xdp)
> +{
> + struct xdp_frame *xdpf = xdp_convert_buff_to_frame(xdp);
> + int cpu = smp_processor_id();
> + struct netdev_queue *nq;
> + int queue;
> + int res;
> +
> + if (unlikely(!xdpf))
> + return -EFAULT;
Can you return -EFAULT here? looks like the function is otherwise
returning positive STMMAC_XDP_* return codes/masks.
> + queue = stmmac_xdp_get_tx_queue(priv, cpu);
> + nq = netdev_get_tx_queue(priv->dev, queue);
> +
> + __netif_tx_lock(nq, cpu);
> + /* Avoids TX time-out as we are sharing with slow path */
> + nq->trans_start = jiffies;
> + res = stmmac_xdp_xmit_xdpf(priv, queue, xdpf);
> + if (res == STMMAC_XDP_TX) {
> + stmmac_flush_tx_descriptors(priv, queue);
> + stmmac_tx_timer_arm(priv, queue);
Would it make sense to arm the timer and flush descriptors at the end
of the NAPI poll cycle? Instead of after every TX frame?
> + }
> + __netif_tx_unlock(nq);
> +
> + return res;
> +}
> @@ -4365,16 +4538,26 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue)
> xdp.data_hard_start = page_address(buf->page);
> xdp_set_data_meta_invalid(&xdp);
> xdp.frame_sz = buf_sz;
> + xdp.rxq = &rx_q->xdp_rxq;
>
> + pre_len = xdp.data_end - xdp.data_hard_start -
> + buf->page_offset;
> skb = stmmac_xdp_run_prog(priv, &xdp);
> + /* Due xdp_adjust_tail: DMA sync for_device
> + * cover max len CPU touch
> + */
> + sync_len = xdp.data_end - xdp.data_hard_start -
> + buf->page_offset;
> + sync_len = max(sync_len, pre_len);
>
> /* For Not XDP_PASS verdict */
> if (IS_ERR(skb)) {
> unsigned int xdp_res = -PTR_ERR(skb);
>
> if (xdp_res & STMMAC_XDP_CONSUMED) {
> - page_pool_recycle_direct(rx_q->page_pool,
> - buf->page);
> + page_pool_put_page(rx_q->page_pool,
> + virt_to_head_page(xdp.data),
> + sync_len, true);
IMHO the dma_sync_size logic is a little question, but it's not really
related to your patch, others are already doing the same thing, so it's
fine, I guess.
> buf->page = NULL;
> priv->dev->stats.rx_dropped++;
