netdev - RE: [PATCH v4 bpf-next 02/10] ice: allow toggling loopback mode via ndo_set

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Date:   Fri, 17 Jun 2022 18:57:41 -0700
From:   John Fastabend <john.fastabend@...il.com>
To:     Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        bpf@...r.kernel.org, ast@...nel.org, daniel@...earbox.net
Cc:     netdev@...r.kernel.org, magnus.karlsson@...el.com,
        bjorn@...nel.org, kuba@...nel.org,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        Alexandr Lobakin <alexandr.lobakin@...el.com>
Subject: RE: [PATCH v4 bpf-next 02/10] ice: allow toggling loopback mode via
 ndo_set_features callback

Maciej Fijalkowski wrote:
> Add support for NETIF_F_LOOPBACK. This feature can be set via:
> $ ethtool -K eth0 loopback <on|off>
> 
> Feature can be useful for local data path tests.
> 
> CC: Alexandr Lobakin <alexandr.lobakin@...el.com>
> Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> ---

Patch looks fine one question about that ice_set_features() function
though.

Acked-by: John Fastabend <john.fastabend@...il.com>

[...]

> +/**
> + * ice_set_loopback - turn on/off loopback mode on underlying PF
> + * @vsi: ptr to VSI
> + * @ena: flag to indicate the on/off setting
> + */
> +static int
> +ice_set_loopback(struct ice_vsi *vsi, bool ena)
> +{
> +	bool if_running = netif_running(vsi->netdev);
> +	int ret;
> +
> +	if (if_running && !test_and_set_bit(ICE_VSI_DOWN, vsi->state)) {
> +		ret = ice_down(vsi);
> +		if (ret) {
> +			netdev_err(vsi->netdev, "Preparing device to toggle loopback failed\n");
> +			return ret;
> +		}
> +	}
> +	ret = ice_aq_set_mac_loopback(&vsi->back->hw, ena, NULL);
> +	if (ret)
> +		netdev_err(vsi->netdev, "Failed to toggle loopback state\n");
> +	if (if_running)
> +		ret = ice_up(vsi);
> +
> +	return ret;
> +}
> +
>  /**
>   * ice_set_features - set the netdev feature flags
>   * @netdev: ptr to the netdev being adjusted
> @@ -5960,7 +5988,10 @@ ice_set_features(struct net_device *netdev, netdev_features_t features)
>  		      clear_bit(ICE_FLAG_CLS_FLOWER, pf->flags);
>  	}
>  
> -	return 0;
> +	if (changed & NETIF_F_LOOPBACK)
> +		ret = ice_set_loopback(vsi, !!(features & NETIF_F_LOOPBACK));
> +
> +	return ret;

Unrelated to your patch, but because you are messing with 'ret' here a bit,
how come you return 0 when ice_is_safe_mode() shouldn't you push that
error up so the user who is doing the setting knows it didn't actually
work?

>  }
>  
>  /**
> -- 
> 2.27.0
>