netdev - Re: [PATCH net-next v6 3/9] bnxt_en: add support for tcp-data-split ethtool command

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Message-ID: <CAMArcTXAm9_zMN0g_2pECbz3855xN48wvkwrO0gnPovy92nt8g@mail.gmail.com>
Date: Thu, 19 Dec 2024 23:05:30 +0900
From: Taehee Yoo <ap420073@...il.com>
To: Jakub Kicinski <kuba@...nel.org>
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	Andy Gospodarek <gospo@...adcom.com>
Subject: Re: [PATCH net-next v6 3/9] bnxt_en: add support for tcp-data-split
 ethtool command

On Thu, Dec 19, 2024 at 11:25 AM Jakub Kicinski <kuba@...nel.org> wrote:
>
> On Wed, 18 Dec 2024 14:45:24 +0000 Taehee Yoo wrote:
> > +     if (tcp_data_split == ETHTOOL_TCP_DATA_SPLIT_DISABLED && hds_config_mod)
> > +             return -EOPNOTSUPP;
>
> I think ethtool ops generally return -EINVAL when param not supported.
> EOPNOTSUPP means entire op is not supported (again, that's just how
> ethtool ops generally work, not a kernel-wide rule).

Thanks! I will use -EINVAL instead of EOPNOTSUPP.

>
> > +     if (tcp_data_split == ETHTOOL_TCP_DATA_SPLIT_ENABLED &&
> > +         hds_config_mod && BNXT_RX_PAGE_MODE(bp)) {
>
> Looks like patch 4 adds this check in the core. I think adding the
> check in the core can be a separate patch. If you put it before this
> patch in the series this bnxt check can be removed?
>
> I mean this chunk in the core:
>
> +       hds_config_mod = old_hds_config != kernel_ringparam.tcp_data_split;
> +       if (kernel_ringparam.tcp_data_split == ETHTOOL_TCP_DATA_SPLIT_ENABLED &&
> +           hds_config_mod && dev_xdp_sb_prog_count(dev)) {
> +               NL_SET_ERR_MSG(info->extack,
> +                              "tcp-data-split can not be enabled with single buffer XDP");
> +               return -EINVAL;
> +       }
>

Right, The core checks single buffer XDP.
But there was a review that bnxt_en driver doesn't support both
single and multi buffer XDP if HDS is in use.
So, this is the reason why logic exists.

> It's currently in the hds-thresh patch but really it's unrelated
> to the threshold..

Thanks, I will move this code to a HDS related patch, not hds-threshold,
or create new patch for this.

>
> > +             NL_SET_ERR_MSG_MOD(extack, "tcp-data-split is disallowed when XDP is attached");
> > +             return -EOPNOTSUPP;
> > +     }
> > +
> >       if (netif_running(dev))
> >               bnxt_close_nic(bp, false, false);
> >
> > +     if (hds_config_mod) {
> > +             if (tcp_data_split == ETHTOOL_TCP_DATA_SPLIT_ENABLED)
> > +                     bp->flags |= BNXT_FLAG_HDS;
> > +             else if (tcp_data_split == ETHTOOL_TCP_DATA_SPLIT_UNKNOWN)
> > +                     bp->flags &= ~BNXT_FLAG_HDS;
> > +     }
> > +
> >       bp->rx_ring_size = ering->rx_pending;
> >       bp->tx_ring_size = ering->tx_pending;
> >       bnxt_set_ring_params(bp);
> > @@ -5354,6 +5374,7 @@ const struct ethtool_ops bnxt_ethtool_ops = {
> >                                    ETHTOOL_COALESCE_STATS_BLOCK_USECS |
> >                                    ETHTOOL_COALESCE_USE_ADAPTIVE_RX |
> >                                    ETHTOOL_COALESCE_USE_CQE,
> > +     .supported_ring_params  = ETHTOOL_RING_USE_TCP_DATA_SPLIT,
> >       .get_link_ksettings     = bnxt_get_link_ksettings,
> >       .set_link_ksettings     = bnxt_set_link_ksettings,
> >       .get_fec_stats          = bnxt_get_fec_stats,
> > diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c
> > index f88b641533fc..1bfff7f29310 100644
> > --- a/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c
> > +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_xdp.c
> > @@ -395,6 +395,10 @@ static int bnxt_xdp_set(struct bnxt *bp, struct bpf_prog *prog)
> >                           bp->dev->mtu, BNXT_MAX_PAGE_MODE_MTU);
> >               return -EOPNOTSUPP;
> >       }
> > +     if (prog && bp->flags & BNXT_FLAG_HDS) {
> > +             netdev_warn(dev, "XDP is disallowed when HDS is enabled.\n");
> > +             return -EOPNOTSUPP;
> > +     }
>
> And this check should also live in the core, now that core has access
> to dev->ethtool->hds_config ? I think you can add this check to the
> core in the same patch as the chunk referred to above.

The bnxt_en disallows setting up both single and multi buffer XDP, but core
checks only single buffer XDP. So, if multi buffer XDP is attaching to
the bnxt_en driver when HDS is enabled, the core can't filter it.

Thanks a lot!
Taehee Yoo