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SubjectRe: [RFC PATCH 3/3] net: ethernet: ti: cpsw: add XDP support
On Wed, 17 Apr 2019 20:49:42 +0300, Ivan Khoronzhuk wrote:
> Add XDP support based on rx page_pool allocator, one frame per page.
> This patch was verified with af_xdp and xdp drop. Page pool allocator
> is used with assumption that only one rx_handler is running
> simultaneously. DMA map/unmap is reused from page pool despite there
> is no need to map whole page.
>
> Due to specific of cpsw, the same TX/RX handler can be used by 2
> network devices, so special fields in buffer are added to identify
> an interface the frame is destined to.
>
> XDP prog is common for all channels till appropriate changes are added
> in XDP infrastructure.
>
> Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>

> @@ -902,22 +947,169 @@ static void cpsw_rx_vlan_encap(struct sk_buff *skb)
> }
> }
>
> +static inline int cpsw_tx_submit_xdpf(struct cpsw_priv *priv,
> + struct xdp_frame *xdpf,
> + struct cpdma_chan *txch)
> +{
> + struct cpsw_common *cpsw = priv->cpsw;
> +
> + return cpdma_chan_submit(txch, cpsw_xdpf_to_handle(xdpf), xdpf->data,
> + xdpf->len,
> + priv->emac_port + cpsw->data.dual_emac);
> +}
> +
> +static int cpsw_xdp_tx_frame(struct cpsw_priv *priv, struct xdp_frame *frame)
> +{
> + struct cpsw_common *cpsw = priv->cpsw;
> + struct cpsw_meta_xdp *xmeta;
> + struct cpdma_chan *txch;
> + int ret = 0;
> +
> + frame->metasize = sizeof(struct cpsw_meta_xdp);
> + xmeta = frame->data - frame->metasize;
> + xmeta->ndev = priv->ndev;
> + xmeta->ch = 0;
> +
> + txch = cpsw->txv[0].ch;
> + ret = cpsw_tx_submit_xdpf(priv, frame, txch);
> + if (ret) {
> + xdp_return_frame_rx_napi(frame);
> + ret = -1;
> + }
> +
> + /* If there is no more tx desc left free then we need to
> + * tell the kernel to stop sending us tx frames.
> + */

So you're using the same TX ring for XDP and stack? How does that
work? The stack's TX ring has a lock, and can be used from any CPU,
while XDP TX rings are per-PCU, no?

> + if (unlikely(!cpdma_check_free_tx_desc(txch))) {
> + struct netdev_queue *txq = netdev_get_tx_queue(priv->ndev, 0);
> +
> + netif_tx_stop_queue(txq);
> +
> + /* Barrier, so that stop_queue visible to other cpus */
> + smp_mb__after_atomic();
> +
> + if (cpdma_check_free_tx_desc(txch))
> + netif_tx_wake_queue(txq);
> + }
> +
> + return ret;
> +}

> +static struct page_pool *cpsw_create_rx_pool(struct cpsw_common *cpsw)
> +{
> + struct page_pool_params pp_params = { 0 };
> +
> + pp_params.order = 0;
> + pp_params.flags = PP_FLAG_DMA_MAP;
> +
> + /* set it to number of descriptors to be cached from init? */
> + pp_params.pool_size = descs_pool_size;
> + pp_params.nid = NUMA_NO_NODE; /* no numa */
> + pp_params.dma_dir = DMA_FROM_DEVICE;

DMA_FROM_DEVICE looks suspicious if you support TX, shouldn't this be
BIDIRECTIONAL?

> + pp_params.dev = cpsw->dev;
> +
> + return page_pool_create(&pp_params);
> +}

> static int cpsw_rx_handler(void *token, int len, int status)
> {
> - struct cpdma_chan *ch;
> - struct sk_buff *skb = token;
> - struct sk_buff *new_skb;
> - struct net_device *ndev = skb->dev;
> - int ret = 0, port;
> - struct cpsw_common *cpsw = ndev_to_cpsw(ndev);
> + struct page *new_page, *page = token;
> + struct cpsw_meta_xdp *new_xmeta, *xmeta = page_address(page);
> + struct cpsw_common *cpsw = ndev_to_cpsw(xmeta->ndev);
> + int pkt_size = cpsw->rx_packet_max;
> + int ret = 0, port, ch = xmeta->ch;
> + struct page_pool *pool = cpsw->rx_page_pool;
> + int headroom = CPSW_HEADROOM;
> + struct net_device *ndev = xmeta->ndev;
> + int flush = 0;
> struct cpsw_priv *priv;
> + struct sk_buff *skb;
> + struct xdp_buff xdp;
> + dma_addr_t dma;
>
> if (cpsw->data.dual_emac) {
> port = CPDMA_RX_SOURCE_PORT(status);
> - if (port) {
> + if (port)
> ndev = cpsw->slaves[--port].ndev;
> - skb->dev = ndev;
> - }
> }
>
> if (unlikely(status < 0) || unlikely(!netif_running(ndev))) {
> @@ -930,47 +1122,105 @@ static int cpsw_rx_handler(void *token, int len, int status)
> * in reducing of the number of rx descriptor in
> * DMA engine, requeue skb back to cpdma.
> */
> - new_skb = skb;
> + new_page = page;
> + new_xmeta = xmeta;
> goto requeue;
> }
>
> /* the interface is going down, skbs are purged */
> - dev_kfree_skb_any(skb);
> + page_pool_recycle_direct(pool, page);
> return 0;
> }
>
> - new_skb = netdev_alloc_skb_ip_align(ndev, cpsw->rx_packet_max);
> - if (new_skb) {
> - skb_copy_queue_mapping(new_skb, skb);
> - skb_put(skb, len);
> - if (status & CPDMA_RX_VLAN_ENCAP)
> - cpsw_rx_vlan_encap(skb);
> - priv = netdev_priv(ndev);
> - if (priv->rx_ts_enabled)
> - cpts_rx_timestamp(cpsw->cpts, skb);
> - skb->protocol = eth_type_trans(skb, ndev);
> - netif_receive_skb(skb);
> - ndev->stats.rx_bytes += len;
> - ndev->stats.rx_packets++;
> - kmemleak_not_leak(new_skb);
> - } else {
> + new_page = cpsw_alloc_page(cpsw);
> + if (unlikely(!new_page)) {
> + new_page = page;
> + new_xmeta = xmeta;
> ndev->stats.rx_dropped++;
> - new_skb = skb;
> + goto requeue;
> }
> + new_xmeta = page_address(new_page);
> +
> + priv = netdev_priv(ndev);
> + if (priv->xdp_prog) {
> + xdp_set_data_meta_invalid(&xdp);
> +
> + if (status & CPDMA_RX_VLAN_ENCAP) {
> + xdp.data = (u8 *)xmeta + CPSW_HEADROOM +
> + CPSW_RX_VLAN_ENCAP_HDR_SIZE;
> + xdp.data_end = xdp.data + len -
> + CPSW_RX_VLAN_ENCAP_HDR_SIZE;
> + } else {
> + xdp.data = (u8 *)xmeta + CPSW_HEADROOM;
> + xdp.data_end = xdp.data + len;
> + }
> +
> + xdp.data_hard_start = xmeta;
> + xdp.rxq = &priv->xdp_rxq[ch];
> +
> + ret = cpsw_run_xdp(priv, &cpsw->rxv[ch], &xdp);
> + if (ret) {
> + if (ret == 2)
> + flush = 1;
> +
> + goto requeue;
> + }
> +
> + /* XDP prog might have changed packet data and boundaries */
> + len = xdp.data_end - xdp.data;
> + headroom = xdp.data - xdp.data_hard_start;
> + }
> +
> + /* Build skb and pass it to networking stack if XDP off or XDP prog
> + * returned XDP_PASS
> + */
> + skb = build_skb(xmeta, cpsw_rxbuf_total_len(pkt_size));
> + if (!skb) {
> + ndev->stats.rx_dropped++;
> + page_pool_recycle_direct(pool, page);
> + goto requeue;
> + }
> +
> + skb_reserve(skb, headroom);
> + skb_put(skb, len);
> + skb->dev = ndev;
> + if (status & CPDMA_RX_VLAN_ENCAP)
> + cpsw_rx_vlan_encap(skb);
> + if (priv->rx_ts_enabled)
> + cpts_rx_timestamp(cpsw->cpts, skb);
> + skb->protocol = eth_type_trans(skb, ndev);
> +
> + /* as cpsw handles one packet per NAPI recycle page before increasing
> + * refcounter, holding this in page pool cache
> + */
> + page_pool_recycle_direct(pool, page);
> +
> + /* it's decremented by netstack after what can be allocated
> + * in cpsw_alloc_page()
> + */
> + page_ref_inc(page);
> + netif_receive_skb(skb);
> +
> + ndev->stats.rx_bytes += len;
> + ndev->stats.rx_packets++;
>
> requeue:
> if (netif_dormant(ndev)) {
> - dev_kfree_skb_any(new_skb);
> - return 0;
> + page_pool_recycle_direct(pool, new_page);
> + return flush;
> }
>
> - ch = cpsw->rxv[skb_get_queue_mapping(new_skb)].ch;
> - ret = cpdma_chan_submit(ch, new_skb, new_skb->data,
> - skb_tailroom(new_skb), 0);
> + new_xmeta->ndev = ndev;
> + new_xmeta->ch = ch;
> + dma = new_page->dma_addr + CPSW_HEADROOM;
> + ret = cpdma_chan_submit_mapped(cpsw->rxv[ch].ch, new_page, (void *)dma,
> + pkt_size, 0);
> if (WARN_ON(ret < 0))
> - dev_kfree_skb_any(new_skb);
> + page_pool_recycle_direct(pool, new_page);
> + else
> + kmemleak_not_leak(new_xmeta); /* Is it needed? */
>
> - return 0;
> + return flush;
> }

On a quick scan I don't see DMA syncs, does the DMA driver takes care
of making sure the DMA sync happens?

> static void cpsw_split_res(struct net_device *ndev)

> @@ -2684,6 +2949,63 @@ static int cpsw_ndo_setup_tc(struct net_device *ndev, enum tc_setup_type type,
> }
> }
>
> +static int cpsw_xdp_prog_setup(struct net_device *ndev, struct bpf_prog *prog)
> +{
> + struct cpsw_priv *priv = netdev_priv(ndev);
> + struct bpf_prog *old_prog;
> +
> + if (!priv->xdp_prog && !prog)
> + return 0;
> +
> + old_prog = xchg(&priv->xdp_prog, prog);
> + if (old_prog)
> + bpf_prog_put(old_prog);
> +
> + return 0;
> +}
> +
> +static int cpsw_ndo_bpf(struct net_device *ndev, struct netdev_bpf *bpf)
> +{
> + struct cpsw_priv *priv = netdev_priv(ndev);
> +
> + switch (bpf->command) {
> + case XDP_SETUP_PROG:
> + return cpsw_xdp_prog_setup(ndev, bpf->prog);
> +
> + case XDP_QUERY_PROG:
> + bpf->prog_id = priv->xdp_prog ? priv->xdp_prog->aux->id : 0;

Consider using xdp_attachment_query() and friends. This way you'll
also return the flags.

> + return 0;
> +
> + default:
> + return -EINVAL;
> + }
> +}
> +
> +static int cpsw_ndo_xdp_xmit(struct net_device *ndev, int n,
> + struct xdp_frame **frames, u32 flags)
> +{
> + struct cpsw_priv *priv = netdev_priv(ndev);
> + struct xdp_frame *xdpf;
> + int i, drops = 0;
> +
> + if (unlikely(flags & ~XDP_XMIT_FLAGS_MASK))
> + return -EINVAL;
> +
> + for (i = 0; i < n; i++) {
> + xdpf = frames[i];
> + if (xdpf->len < CPSW_MIN_PACKET_SIZE) {
> + xdp_return_frame_rx_napi(xdpf);
> + drops++;
> + continue;
> + }
> +
> + if (cpsw_xdp_tx_frame(priv, xdpf))
> + drops++;
> + }
> +
> + return n - drops;
> +}
> +
> static const struct net_device_ops cpsw_netdev_ops = {
> .ndo_open = cpsw_ndo_open,
> .ndo_stop = cpsw_ndo_stop,
> @@ -2700,6 +3022,8 @@ static const struct net_device_ops cpsw_netdev_ops = {
> .ndo_vlan_rx_add_vid = cpsw_ndo_vlan_rx_add_vid,
> .ndo_vlan_rx_kill_vid = cpsw_ndo_vlan_rx_kill_vid,
> .ndo_setup_tc = cpsw_ndo_setup_tc,
> + .ndo_bpf = cpsw_ndo_bpf,
> + .ndo_xdp_xmit = cpsw_ndo_xdp_xmit,
> };
>
> static int cpsw_get_regs_len(struct net_device *ndev)
> @@ -2920,6 +3244,57 @@ static int cpsw_check_ch_settings(struct cpsw_common *cpsw,
> return 0;
> }
>
> +static void cpsw_xdp_rxq_unreg(struct cpsw_common *cpsw, int ch)
> +{
> + struct cpsw_slave *slave;
> + struct cpsw_priv *priv;
> + int i;
> +
> + for (i = cpsw->data.slaves, slave = cpsw->slaves; i; i--, slave++) {
> + if (!slave->ndev)
> + continue;
> +
> + priv = netdev_priv(slave->ndev);
> + xdp_rxq_info_unreg(&priv->xdp_rxq[ch]);
> + }
> +}
> +
> +static int cpsw_xdp_rxq_reg(struct cpsw_common *cpsw, int ch)
> +{
> + struct cpsw_slave *slave;
> + struct cpsw_priv *priv;
> + int i, ret;
> +
> + /* As channels are common for both ports sharing same queues, xdp_rxq
> + * information also becomes shared and used by every packet on this
> + * channel. But exch xdp_rxq holds link on netdev, which by the theory
> + * can have different memory model and so, network device must hold it's
> + * own set of rxq and thus both netdevs should be prepared
> + */
> + for (i = cpsw->data.slaves, slave = cpsw->slaves; i; i--, slave++) {
> + if (!slave->ndev)
> + continue;
> +
> + priv = netdev_priv(slave->ndev);
> +
> + ret = xdp_rxq_info_reg(&priv->xdp_rxq[ch], priv->ndev, ch);
> + if (ret)
> + goto err;
> +
> + ret = xdp_rxq_info_reg_mem_model(&priv->xdp_rxq[ch],
> + MEM_TYPE_PAGE_POOL,
> + cpsw->rx_page_pool);
> + if (ret)
> + goto err;
> + }
> +
> + return ret;
> +
> +err:
> + cpsw_xdp_rxq_unreg(cpsw, ch);
> + return ret;
> +}
> +
> static int cpsw_update_channels_res(struct cpsw_priv *priv, int ch_num, int rx)
> {
> struct cpsw_common *cpsw = priv->cpsw;
> @@ -2950,6 +3325,11 @@ static int cpsw_update_channels_res(struct cpsw_priv *priv, int ch_num, int rx)
> if (!vec[*ch].ch)
> return -EINVAL;
>
> + if (rx && cpsw_xdp_rxq_reg(cpsw, *ch)) {
> + cpdma_chan_destroy(vec[*ch].ch);
> + return -EINVAL;
> + }
> +
> cpsw_info(priv, ifup, "created new %d %s channel\n", *ch,
> (rx ? "rx" : "tx"));
> (*ch)++;
> @@ -2958,6 +3338,9 @@ static int cpsw_update_channels_res(struct cpsw_priv *priv, int ch_num, int rx)
> while (*ch > ch_num) {
> (*ch)--;
>
> + if (rx)
> + cpsw_xdp_rxq_unreg(cpsw, *ch);
> +
> ret = cpdma_chan_destroy(vec[*ch].ch);
> if (ret)
> return ret;
> @@ -3446,6 +3829,15 @@ static int cpsw_probe_dual_emac(struct cpsw_priv *priv)
> ndev->netdev_ops = &cpsw_netdev_ops;
> ndev->ethtool_ops = &cpsw_ethtool_ops;
>
> + ret = xdp_rxq_info_reg(&priv_sl2->xdp_rxq[0], ndev, 0);
> + if (ret)
> + return ret;
> +
> + ret = xdp_rxq_info_reg_mem_model(&priv_sl2->xdp_rxq[0],
> + MEM_TYPE_PAGE_SHARED, NULL);
> + if (ret)
> + return ret;
> +
> /* register the network device */
> SET_NETDEV_DEV(ndev, cpsw->dev);
> ret = register_netdev(ndev);
> @@ -3517,6 +3909,12 @@ static int cpsw_probe(struct platform_device *pdev)
> goto clean_ndev_ret;
> }
>
> + cpsw->rx_page_pool = cpsw_create_rx_pool(cpsw);
> + if (IS_ERR(cpsw->rx_page_pool)) {
> + dev_err(&pdev->dev, "create rx page pool\n");
> + goto clean_ndev_ret;
> + }
> +
> /*
> * This may be required here for child devices.
> */
> @@ -3663,20 +4061,31 @@ static int cpsw_probe(struct platform_device *pdev)
> cpsw->quirk_irq = 1;
>
> ch = cpsw->quirk_irq ? 0 : 7;
> - cpsw->txv[0].ch = cpdma_chan_create(cpsw->dma, ch, cpsw_tx_handler, 0);
> + cpsw->txv[0].ch =
> + cpdma_chan_create(cpsw->dma, ch, cpsw_tx_handler, 0);
> if (IS_ERR(cpsw->txv[0].ch)) {
> dev_err(priv->dev, "error initializing tx dma channel\n");
> ret = PTR_ERR(cpsw->txv[0].ch);
> goto clean_dma_ret;
> }
>
> - cpsw->rxv[0].ch = cpdma_chan_create(cpsw->dma, 0, cpsw_rx_handler, 1);
> + cpsw->rxv[0].ch =
> + cpdma_chan_create(cpsw->dma, 0, cpsw_rx_handler, 1);
> if (IS_ERR(cpsw->rxv[0].ch)) {
> dev_err(priv->dev, "error initializing rx dma channel\n");
> ret = PTR_ERR(cpsw->rxv[0].ch);
> goto clean_dma_ret;
> }
>
> + ret = xdp_rxq_info_reg(&priv->xdp_rxq[0], ndev, 0);
> + if (ret)
> + goto clean_dma_ret;
> +
> + ret = xdp_rxq_info_reg_mem_model(&priv->xdp_rxq[0], MEM_TYPE_PAGE_POOL,
> + cpsw->rx_page_pool);
> + if (ret)
> + goto clean_dma_ret;
> +
> ale_params.dev = &pdev->dev;
> ale_params.ale_ageout = ale_ageout;
> ale_params.ale_entries = data->ale_entries;

I think you need to unreg the mem model somewhere on the failure path,
no?


> @@ -3786,6 +4195,7 @@ static int cpsw_probe(struct platform_device *pdev)
> pm_runtime_put_sync(&pdev->dev);
> clean_runtime_disable_ret:
> pm_runtime_disable(&pdev->dev);
> + page_pool_destroy(cpsw->rx_page_pool);
> clean_ndev_ret:
> free_netdev(priv->ndev);
> return ret;
> @@ -3809,6 +4219,7 @@ static int cpsw_remove(struct platform_device *pdev)
>
> cpts_release(cpsw->cpts);
> cpdma_ctlr_destroy(cpsw->dma);
> + page_pool_destroy(cpsw->rx_page_pool);
> cpsw_remove_dt(pdev);
> pm_runtime_put_sync(&pdev->dev);
> pm_runtime_disable(&pdev->dev);

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