netdev - Re: [PATCH net 2/4] bnxt_en: Flush XDP for bnxt_poll

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Date: Fri, 8 Sep 2023 22:00:20 +0530
From: Pavan Chebbi <pavan.chebbi@...adcom.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: netdev@...r.kernel.org, bpf@...r.kernel.org, 
	"David S. Miller" <davem@...emloft.net>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Eric Dumazet <edumazet@...gle.com>, 
	Jakub Kicinski <kuba@...nel.org>, Jesper Dangaard Brouer <hawk@...nel.org>, 
	John Fastabend <john.fastabend@...il.com>, Paolo Abeni <pabeni@...hat.com>, 
	Thomas Gleixner <tglx@...utronix.de>, Michael Chan <michael.chan@...adcom.com>
Subject: Re: [PATCH net 2/4] bnxt_en: Flush XDP for bnxt_poll_nitroa0()'s NAPI

On Fri, Sep 8, 2023 at 7:29 PM Sebastian Andrzej Siewior
<bigeasy@...utronix.de> wrote:
>
> bnxt_poll_nitroa0() invokes bnxt_rx_pkt() which can run a XDP program
> which in turn can return XDP_REDIRECT. bnxt_rx_pkt() is also used by
> __bnxt_poll_work() which flushes (xdp_do_flush()) the packets after each
> round. bnxt_poll_nitroa0() lacks this feature.
> xdp_do_flush() should be invoked before leaving the NAPI callback.
>
> Invoke xdp_do_flush() after a redirect in bnxt_poll_nitroa0() NAPI.
>
> Cc: Michael Chan <michael.chan@...adcom.com>
> Fixes: f18c2b77b2e4e ("bnxt_en: optimized XDP_REDIRECT support")
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> ---
>  drivers/net/ethernet/broadcom/bnxt/bnxt.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> index 5cc0dbe121327..7551aa8068f8f 100644
> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
> @@ -2614,6 +2614,7 @@ static int bnxt_poll_nitroa0(struct napi_struct *napi, int budget)
>         struct rx_cmp_ext *rxcmp1;
>         u32 cp_cons, tmp_raw_cons;
>         u32 raw_cons = cpr->cp_raw_cons;
> +       bool flush_xdp = false;

Michael can confirm but I don't think we need this additional variable.
Since the event is always ORed, we could directly check if (event &
BNXT_REDIRECT_EVENT) just like is done in __bnxt_poll_work().

>         u32 rx_pkts = 0;
>         u8 event = 0;
>
> @@ -2648,6 +2649,8 @@ static int bnxt_poll_nitroa0(struct napi_struct *napi, int budget)
>                                 rx_pkts++;
>                         else if (rc == -EBUSY)  /* partial completion */
>                                 break;
> +                       if (event & BNXT_REDIRECT_EVENT)
> +                               flush_xdp = true;
>                 } else if (unlikely(TX_CMP_TYPE(txcmp) ==
>                                     CMPL_BASE_TYPE_HWRM_DONE)) {
>                         bnxt_hwrm_handler(bp, txcmp);
> @@ -2667,6 +2670,8 @@ static int bnxt_poll_nitroa0(struct napi_struct *napi, int budget)
>
>         if (event & BNXT_AGG_EVENT)
>                 bnxt_db_write(bp, &rxr->rx_agg_db, rxr->rx_agg_prod);
> +       if (flush_xdp)
> +               xdp_do_flush();
>
>         if (!bnxt_has_work(bp, cpr) && rx_pkts < budget) {
>                 napi_complete_done(napi, rx_pkts);
> --
> 2.40.1
>
>

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