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SubjectRe: [PATCH v6 net-next 5/5] net: ethernet: ti: cpsw: add XDP support
On Wed,  3 Jul 2019 13:19:03 +0300
Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org> wrote:

> Add XDP support based on rx page_pool allocator, one frame per page.
> 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. Thus XDP works for both
> interfaces, that allows to test xdp redirect between two interfaces
> easily. Aslo, each rx queue have own page pools, but common for both
> netdevs.
>
> XDP prog is common for all channels till appropriate changes are added
> in XDP infrastructure. Also, once page_pool recycling becomes part of
> skb netstack some simplifications can be added, like removing
> page_pool_release_page() before skb receive.
>
> In order to keep rx_dev while redirect, that can be somehow used in
> future, do flush in rx_handler, that allows to keep rx dev the same
> while reidrect. It allows to conform with tracing rx_dev pointed
> by Jesper.

So, you simply call xdp_do_flush_map() after each xdp_do_redirect().
It will kill RX-bulk and performance, but I guess it will work.

I guess, we can optimized it later, by e.g. in function calling
cpsw_run_xdp() have a variable that detect if net_device changed
(priv->ndev) and then call xdp_do_flush_map() when needed.


> Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
> ---
> drivers/net/ethernet/ti/Kconfig | 1 +
> drivers/net/ethernet/ti/cpsw.c | 485 ++++++++++++++++++++++---
> drivers/net/ethernet/ti/cpsw_ethtool.c | 66 +++-
> drivers/net/ethernet/ti/cpsw_priv.h | 7 +
> 4 files changed, 502 insertions(+), 57 deletions(-)
>
[...]
> +static int cpsw_run_xdp(struct cpsw_priv *priv, int ch, struct xdp_buff *xdp,
> + struct page *page)
> +{
> + struct cpsw_common *cpsw = priv->cpsw;
> + struct net_device *ndev = priv->ndev;
> + int ret = CPSW_XDP_CONSUMED;
> + struct xdp_frame *xdpf;
> + struct bpf_prog *prog;
> + u32 act;
> +
> + rcu_read_lock();
> +
> + prog = READ_ONCE(priv->xdp_prog);
> + if (!prog) {
> + ret = CPSW_XDP_PASS;
> + goto out;
> + }
> +
> + act = bpf_prog_run_xdp(prog, xdp);
> + switch (act) {
> + case XDP_PASS:
> + ret = CPSW_XDP_PASS;
> + break;
> + case XDP_TX:
> + xdpf = convert_to_xdp_frame(xdp);
> + if (unlikely(!xdpf))
> + goto drop;
> +
> + cpsw_xdp_tx_frame(priv, xdpf, page);
> + break;
> + case XDP_REDIRECT:
> + if (xdp_do_redirect(ndev, xdp, prog))
> + goto drop;
> +
> + /* as flush requires rx_dev to be per NAPI handle and there
> + * is can be two devices putting packets on bulk queue,
> + * do flush here avoid this just for sure.
> + */
> + xdp_do_flush_map();

> + break;
> + default:
> + bpf_warn_invalid_xdp_action(act);
> + /* fall through */
> + case XDP_ABORTED:
> + trace_xdp_exception(ndev, prog, act);
> + /* fall through -- handle aborts by dropping packet */
> + case XDP_DROP:
> + goto drop;
> + }
> +out:
> + rcu_read_unlock();
> + return ret;
> +drop:
> + rcu_read_unlock();
> + page_pool_recycle_direct(cpsw->page_pool[ch], page);
> + return ret;
> +}

--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer

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