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SubjectRe: [PATCH v6 net-next 5/5] net: ethernet: ti: cpsw: add XDP support
On Thu, Jul 04, 2019 at 11:19:39AM +0200, Jesper Dangaard Brouer wrote:
>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.

It's problem of cpsw already and can be optimized locally by own
bulk queues for instance, if it will be simple if really needed ofc.

>
>
>> 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

--
Regards,
Ivan Khoronzhuk

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