Re: [PATCH 1/1] net: fec: add initial XDP support

Jesper Dangaard Brouer
2022-09-29T10:16:42Z

On 28/09/2022 17.25, Shenwei Wang wrote:
> This patch adds the initial XDP support to Freescale driver. It supports
> XDP_PASS, XDP_DROP and XDP_REDIRECT actions. Upcoming patches will add
> support for XDP_TX and Zero Copy features.
>
> This patch also optimizes the RX buffers by using the page pool, which
> uses one frame per page for easy management. In the future, it can be
> further improved to use two frames per page.
>
> This patch has been tested with the sample apps of "xdpsock" and "xdp2" in
> samples/bpf directory for both SKB and Native (XDP) mode. The following
> are the testing result comparing with the XDP skb-mode.
>
> # xdpsock -i eth0
> sock0@eth0:0 rxdrop xdp-drv
> pps pkts 1.00
> rx 198798 1040011
> tx 0 0
>
> # xdpsock -S -i eth0 // skb-mode
> sock0@eth0:0 rxdrop xdp-skb
> pps pkts 1.00
> rx 95638 717251
> tx 0 0
>
> # xdp2 eth0
> proto 0: 475362 pkt/s
> proto 0: 475549 pkt/s
> proto 0: 475480 pkt/s
> proto 0: 143258 pkt/s
>
> # xdp2 -S eth0 // skb-mode
> proto 17: 56468 pkt/s
> proto 17: 71999 pkt/s
> proto 17: 72000 pkt/s
> proto 17: 71988 pkt/s
>
> Signed-off-by: Shenwei Wang <shenwei.wang@nxp.com>
> ---
> drivers/net/ethernet/freescale/fec.h | 34 +-
> drivers/net/ethernet/freescale/fec_main.c | 414 +++++++++++++++++++---
> 2 files changed, 393 insertions(+), 55 deletions(-)
>
> diff --git a/drivers/net/ethernet/freescale/fec.h b/drivers/net/ethernet/freescale/fec.h
> index b0100fe3c9e4..f7531503aa95 100644
> --- a/drivers/net/ethernet/freescale/fec.h
> +++ b/drivers/net/ethernet/freescale/fec.h
> @@ -346,8 +346,10 @@ struct bufdesc_ex {
> * the skbuffer directly.
> */
>
> +#define FEC_ENET_XDP_HEADROOM (512) /* XDP_PACKET_HEADROOM + NET_IP_ALIGN) */

Why the large headroom?

> +
> #define FEC_ENET_RX_PAGES 256
> -#define FEC_ENET_RX_FRSIZE 2048
> +#define FEC_ENET_RX_FRSIZE (PAGE_SIZE - FEC_ENET_XDP_HEADROOM)

This FEC_ENET_RX_FRSIZE is likely wrong, because you also need to
reserve 320 bytes at the end for struct skb_shared_info.
(320 calculated as SKB_DATA_ALIGN(sizeof(struct skb_shared_info)))

> #define FEC_ENET_RX_FRPPG (PAGE_SIZE / FEC_ENET_RX_FRSIZE)
> #define RX_RING_SIZE (FEC_ENET_RX_FRPPG * FEC_ENET_RX_PAGES)
> #define FEC_ENET_TX_FRSIZE 2048
> @@ -517,6 +519,22 @@ struct bufdesc_prop {
[...]

> diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
> index 59921218a8a4..2e30182ed770 100644
> --- a/drivers/net/ethernet/freescale/fec_main.c
> +++ b/drivers/net/ethernet/freescale/fec_main.c
> @@ -66,6 +66,8 @@
> #include <linux/mfd/syscon.h>
> #include <linux/regmap.h>
> #include <soc/imx/cpuidle.h>
> +#include <linux/filter.h>
> +#include <linux/bpf.h>
>
> #include <asm/cacheflush.h>
>
> @@ -87,6 +89,11 @@ static const u16 fec_enet_vlan_pri_to_queue[8] = {0, 0, 1, 1, 1, 2, 2, 2};
> #define FEC_ENET_OPD_V 0xFFF0
> #define FEC_MDIO_PM_TIMEOUT 100 /* ms */
>
> +#define FEC_ENET_XDP_PASS 0
> +#define FEC_ENET_XDP_CONSUMED BIT(0)
> +#define FEC_ENET_XDP_TX BIT(1)
> +#define FEC_ENET_XDP_REDIR BIT(2)
> +
> struct fec_devinfo {
> u32 quirks;
> };
> @@ -422,6 +429,49 @@ fec_enet_clear_csum(struct sk_buff *skb, struct net_device *ndev)
> return 0;
> }
>
> +static int
> +fec_enet_create_page_pool(struct fec_enet_private *fep,
> + struct fec_enet_priv_rx_q *rxq, int size)
> +{
> + struct bpf_prog *xdp_prog = READ_ONCE(fep->xdp_prog);
> + struct page_pool_params pp_params = {
> + .order = 0,
> + .flags = PP_FLAG_DMA_MAP | PP_FLAG_DMA_SYNC_DEV,
> + .pool_size = size,
> + .nid = dev_to_node(&fep->pdev->dev),
> + .dev = &fep->pdev->dev,
> + .dma_dir = xdp_prog ? DMA_BIDIRECTIONAL : DMA_FROM_DEVICE,
> + .offset = FEC_ENET_XDP_HEADROOM,
> + .max_len = FEC_ENET_RX_FRSIZE,

XDP BPF-prog cannot access last 320 bytes, so FEC_ENET_RX_FRSIZE is
wrong here.

> + };
> + int err;
> +
> + rxq->page_pool = page_pool_create(&pp_params);
> + if (IS_ERR(rxq->page_pool)) {
> + err = PTR_ERR(rxq->page_pool);
> + rxq->page_pool = NULL;
> + return err;
> + }
> +
> + err = xdp_rxq_info_reg(&rxq->xdp_rxq, fep->netdev, rxq->id, 0);
> + if (err < 0)
> + goto err_free_pp;
> +
> + err = xdp_rxq_info_reg_mem_model(&rxq->xdp_rxq, MEM_TYPE_PAGE_POOL,
> + rxq->page_pool);
> + if (err)
> + goto err_unregister_rxq;
> +
> + return 0;
> +
> +err_unregister_rxq:
> + xdp_rxq_info_unreg(&rxq->xdp_rxq);
> +err_free_pp:
> + page_pool_destroy(rxq->page_pool);
> + rxq->page_pool = NULL;
> + return err;
> +}
> +
> static struct bufdesc *
> fec_enet_txq_submit_frag_skb(struct fec_enet_priv_tx_q *txq,
> struct sk_buff *skb,
> @@ -1285,7 +1335,6 @@ fec_stop(struct net_device *ndev)
> }
> }
>
> -
> static void
> fec_timeout(struct net_device *ndev, unsigned int txqueue)
> {
> @@ -1450,7 +1499,7 @@ static void fec_enet_tx(struct net_device *ndev)
> fec_enet_tx_queue(ndev, i);
> }
>
> -static int
> +static int __maybe_unused
> fec_enet_new_rxbdp(struct net_device *ndev, struct bufdesc *bdp, struct sk_buff *skb)
> {
> struct fec_enet_private *fep = netdev_priv(ndev);
> @@ -1470,8 +1519,9 @@ fec_enet_new_rxbdp(struct net_device *ndev, struct bufdesc *bdp, struct sk_buff
> return 0;
> }
>
> -static bool fec_enet_copybreak(struct net_device *ndev, struct sk_buff **skb,
> - struct bufdesc *bdp, u32 length, bool swap)
> +static bool __maybe_unused
> +fec_enet_copybreak(struct net_device *ndev, struct sk_buff **skb,
> + struct bufdesc *bdp, u32 length, bool swap)
> {
> struct fec_enet_private *fep = netdev_priv(ndev);
> struct sk_buff *new_skb;
> @@ -1496,6 +1546,78 @@ static bool fec_enet_copybreak(struct net_device *ndev, struct sk_buff **skb,
> return true;
> }
>
> +static void fec_enet_update_cbd(struct fec_enet_priv_rx_q *rxq,
> + struct bufdesc *bdp, int index)
> +{
> + struct page *new_page;
> + dma_addr_t phys_addr;
> +
> + new_page = page_pool_dev_alloc_pages(rxq->page_pool);
> + WARN_ON(!new_page);
> + rxq->rx_skb_info[index].page = new_page;
> +
> + rxq->rx_skb_info[index].offset = FEC_ENET_XDP_HEADROOM;
> + phys_addr = page_pool_get_dma_addr(new_page) + FEC_ENET_XDP_HEADROOM;
> + bdp->cbd_bufaddr = cpu_to_fec32(phys_addr);
> +}
> +
> +static u32
> +fec_enet_run_xdp(struct fec_enet_private *fep, struct bpf_prog *prog,
> + struct xdp_buff *xdp, struct fec_enet_priv_rx_q *rxq, int index)
> +{
> + unsigned int sync, len = xdp->data_end - xdp->data;
> + u32 ret = FEC_ENET_XDP_PASS;
> + struct page *page;
> + int err;
> + u32 act;
> +
> + act = bpf_prog_run_xdp(prog, xdp);
> +
> + /* Due xdp_adjust_tail: DMA sync for_device cover max len CPU touch */
> + sync = xdp->data_end - xdp->data_hard_start - FEC_ENET_XDP_HEADROOM;
> + sync = max(sync, len);
> +
> + switch (act) {
> + case XDP_PASS:
> + rxq->stats.xdp_pass++;
> + ret = FEC_ENET_XDP_PASS;
> + break;
> +
> + case XDP_TX:
> + rxq->stats.xdp_tx++;
> + bpf_warn_invalid_xdp_action(fep->netdev, prog, act);
> + fallthrough;

This fallthrough looks wrong. The next xdp_do_redirect() call will
pickup left-overs in per CPU bpf_redirect_info.

> +
> + case XDP_REDIRECT:
> + err = xdp_do_redirect(fep->netdev, xdp, prog);
> + rxq->stats.xdp_redirect++;
> + if (!err) {
> + ret = FEC_ENET_XDP_REDIR;
> + } else {
> + ret = FEC_ENET_XDP_CONSUMED;
> + page = virt_to_head_page(xdp->data);
> + page_pool_put_page(rxq->page_pool, page, sync, true);
> + }
> + break;
> +
> + default:
> + bpf_warn_invalid_xdp_action(fep->netdev, prog, act);
> + fallthrough;
> +
> + case XDP_ABORTED:
> + fallthrough; /* handle aborts by dropping packet */
> +
> + case XDP_DROP:
> + rxq->stats.xdp_drop++;
> + ret = FEC_ENET_XDP_CONSUMED;
> + page = virt_to_head_page(xdp->data);
> + page_pool_put_page(rxq->page_pool, page, sync, true);
> + break;
> + }
> +
> + return ret;
> +}
> +
> /* During a receive, the bd_rx.cur points to the current incoming buffer.
> * When we update through the ring, if the next incoming buffer has
> * not been given to the system, we just set the empty indicator,
> @@ -1508,7 +1630,6 @@ fec_enet_rx_queue(struct net_device *ndev, int budget, u16 queue_id)
> struct fec_enet_priv_rx_q *rxq;
> struct bufdesc *bdp;
> unsigned short status;
> - struct sk_buff *skb_new = NULL;
> struct sk_buff *skb;
> ushort pkt_len;
> __u8 *data;
> @@ -1517,8 +1638,12 @@ fec_enet_rx_queue(struct net_device *ndev, int budget, u16 queue_id)
> bool vlan_packet_rcvd = false;
> u16 vlan_tag;
> int index = 0;
> - bool is_copybreak;
> bool need_swap = fep->quirks & FEC_QUIRK_SWAP_FRAME;
> + struct page *page;
> + struct xdp_buff xdp;
> + u32 ret, xdp_result = FEC_ENET_XDP_PASS;
> +
> + struct bpf_prog *xdp_prog = READ_ONCE(fep->xdp_prog);
>
> #ifdef CONFIG_M532x
> flush_cache_all();
> @@ -1529,6 +1654,7 @@ fec_enet_rx_queue(struct net_device *ndev, int budget, u16 queue_id)
> * These get messed up if we get called due to a busy condition.
> */
> bdp = rxq->bd.cur;
> + xdp_init_buff(&xdp, PAGE_SIZE, &rxq->xdp_rxq);
>
> while (!((status = fec16_to_cpu(bdp->cbd_sc)) & BD_ENET_RX_EMPTY)) {
>
> @@ -1570,31 +1696,37 @@ fec_enet_rx_queue(struct net_device *ndev, int budget, u16 queue_id)
> ndev->stats.rx_bytes += pkt_len;
>
> index = fec_enet_get_bd_index(bdp, &rxq->bd);
> - skb = rxq->rx_skbuff[index];
> + page = rxq->rx_skb_info[index].page;
> +
> + dma_sync_single_for_cpu(&fep->pdev->dev,
> + fec32_to_cpu(bdp->cbd_bufaddr),
> + pkt_len,
> + DMA_FROM_DEVICE);
> +
> + prefetch(page_address(page));
> + fec_enet_update_cbd(rxq, bdp, index);
> +
> + if (xdp_prog) {
> + xdp_prepare_buff(&xdp, page_address(page),
> + FEC_ENET_XDP_HEADROOM, pkt_len, false);
> +
> + ret = fec_enet_run_xdp(fep, xdp_prog, &xdp, rxq, index);
> + xdp_result |= ret;
> + if (ret != FEC_ENET_XDP_PASS)
> + goto rx_processing_done;
> + }
>
> /* The packet length includes FCS, but we don't want to
> * include that when passing upstream as it messes up
> * bridging applications.
> */
> - is_copybreak = fec_enet_copybreak(ndev, &skb, bdp, pkt_len - 4,
> - need_swap);
> - if (!is_copybreak) {
> - skb_new = netdev_alloc_skb(ndev, FEC_ENET_RX_FRSIZE);
> - if (unlikely(!skb_new)) {
> - ndev->stats.rx_dropped++;
> - goto rx_processing_done;
> - }
> - dma_unmap_single(&fep->pdev->dev,
> - fec32_to_cpu(bdp->cbd_bufaddr),
> - FEC_ENET_RX_FRSIZE - fep->rx_align,
> - DMA_FROM_DEVICE);
> - }
> -
> - prefetch(skb->data - NET_IP_ALIGN);
> + skb = build_skb(page_address(page), FEC_ENET_RX_FRSIZE);

This looks wrong, I think FEC_ENET_RX_FRSIZE should be replaced by
PAGE_SIZE.
As build_skb() does:

size -= SKB_DATA_ALIGN(sizeof(struct skb_shared_info));

> + skb_reserve(skb, FEC_ENET_XDP_HEADROOM);

The skb_reserve looks correct.

> skb_put(skb, pkt_len - 4);
> data = skb->data;
> + page_pool_release_page(rxq->page_pool, page);

Today page_pool have SKB recycle support (you might have looked at
drivers that didn't utilize this yet), thus you don't need to release
the page (page_pool_release_page) here. Instead you could simply mark
the SKB for recycling, unless driver does some page refcnt tricks I
didn't notice.

skb_mark_for_recycle(skb);

> - if (!is_copybreak && need_swap)
> + if (need_swap)
> swap_buffer(data, pkt_len);
>
> #if !defined(CONFIG_M5272)
> @@ -1649,16 +1781,6 @@ fec_enet_rx_queue(struct net_device *ndev, int budget, u16 queue_id) …