2018-05-17 23:31 GMT+02:00 Jesper Dangaard Brouer <bro...@redhat.com>:
>
> On Tue, 15 May 2018 21:06:15 +0200 Björn Töpel <bjorn.to...@gmail.com> wrote:
>
>> From: Magnus Karlsson <magnus.karls...@intel.com>
>>
>> Here, the zero-copy ndo is implemented. As a shortcut, the existing
>> XDP Tx rings are used for zero-copy. This means that and XDP program
>> cannot redirect to an AF_XDP enabled XDP Tx ring.
>
> This "shortcut" is not acceptable, and completely broken. The
> XDP_REDIRECT queue_index is based on smp_processor_id(), and can easily
> clash with the configured XSK queue_index. Provided a bit more code
> context below...
>
Yes, and this is the reason we need to go for a solution with
dedicated Tx rings. Again, we chose not to, and simply drops
XDP_REDIRECT where the AF_XDP queue id clashes with the processor id.
The queue id hijacked by AF_XDP's egress side.
> On Tue, 15 May 2018 21:06:15 +0200
> Björn Töpel <bjorn.to...@gmail.com> wrote:
>
> int i40e_xdp_xmit(struct net_device *dev, struct xdp_frame *xdpf)
> {
> 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 -ENETDOWN;
>
>> @@ -4025,6 +4158,9 @@ int i40e_xdp_xmit(struct net_device *dev, struct
>> xdp_frame *xdpf)
>> if (!i40e_enabled_xdp_vsi(vsi) || queue_index >= vsi->num_queue_pairs)
>> return -ENXIO;
>>
>> + if (vsi->xdp_rings[queue_index]->xsk_umem)
>> + return -ENXIO;
>> +
>
> Using the sane errno makes this impossible to debug (via the tracepoints).
>
The rationale was that the situation was similar to an incorrectly
configured receiving (from an XDP_REDIRECT perspective) interface.
We'll rework this! Thanks for looking into this, Jesper!
Björn
>> err = i40e_xmit_xdp_ring(xdpf, vsi->xdp_rings[queue_index]);
>> if (err != I40E_XDP_TX)
>> return -ENOSPC;
>> @@ -4048,5 +4184,34 @@ void i40e_xdp_flush(struct net_device *dev)
>> if (!i40e_enabled_xdp_vsi(vsi) || queue_index >= vsi->num_queue_pairs)
>> return;
>>
>> + if (vsi->xdp_rings[queue_index]->xsk_umem)
>> + return;
>> +
>> i40e_xdp_ring_update_tail(vsi->xdp_rings[queue_index]);
>> }
>
>
>
> --
> Best regards,
> Jesper Dangaard Brouer
> MSc.CS, Principal Kernel Engineer at Red Hat
> LinkedIn: http://www.linkedin.com/in/brouer
