netdev - Re: [PATCH v2 2/2] i40e: add support for XDP

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Date:   Thu, 22 Mar 2018 13:20:21 +0100
From:   Björn Töpel <bjorn.topel@...il.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        intel-wired-lan <intel-wired-lan@...ts.osuosl.org>,
        Björn Töpel <bjorn.topel@...el.com>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        Netdev <netdev@...r.kernel.org>,
        "Duyck, Alexander H" <alexander.h.duyck@...el.com>,
        Alexander Duyck <alexander.duyck@...il.com>
Subject: Re: [PATCH v2 2/2] i40e: add support for XDP_REDIRECT

2018-03-22 12:58 GMT+01:00 Jesper Dangaard Brouer <brouer@...hat.com>:
>
> On Thu, 22 Mar 2018 10:03:07 +0100 Björn Töpel <bjorn.topel@...il.com> wrote:
>
>> +/**
>> + * i40e_xdp_xmit - Implements ndo_xdp_xmit
>> + * @dev: netdev
>> + * @xdp: XDP buffer
>> + *
>> + * Returns Zero if sent, else an error code
>> + **/
>> +int i40e_xdp_xmit(struct net_device *dev, struct xdp_buff *xdp)
>> +{
>
> The return code is used by the XDP redirect tracepoint... this is the
> only way we have to debug/troubleshoot runtime issues with XDP. Thus,
> these need to be consistent across drives and distinguishable.
>

Thanks for pointing this out! I'll address all your comments and do a
respin (but I'll wait for Alex' comments, if any).


Björn

>> +     struct i40e_netdev_priv *np = netdev_priv(dev);
>> +     unsigned int queue_index = smp_processor_id();
>> +     struct i40e_vsi *vsi = np->vsi;
>> +     int err;
>> +
>> +     if (test_bit(__I40E_VSI_DOWN, vsi->state))
>> +             return -EINVAL;
>
> Should be: -ENETDOWN
>
>> +
>> +     if (!i40e_enabled_xdp_vsi(vsi) || queue_index >= vsi->num_queue_pairs)
>> +             return -EINVAL;
>
> Should be: -ENXIO
>
>> +     err = i40e_xmit_xdp_ring(xdp, vsi->xdp_rings[queue_index]);
>> +     if (err != I40E_XDP_TX)
>> +             return -ENOMEM;
>
> Should be: -ENOSPC
>
> The ENOSPC return code is important, as this can be used as a feedback
> to a XDP_REDIRECT load-balancer facility.
>
> --
> Best regards,
>   Jesper Dangaard Brouer
>   MSc.CS, Principal Kernel Engineer at Red Hat
>   LinkedIn: http://www.linkedin.com/in/brouer