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

From: Jakub Kicinski <[email-masked]>
Date: Wed, 18 Dec 2024 18:25:47 -0800

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).

> +	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;
+	}

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

> +		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.