Subject: Re: [net PATCH v3 3/5] virtio_net: factor out xdp handler for readability

From: John Fastabend <[email-masked]>
Date: Fri, 13 Jan 2017 11:56:57 -0800

On 17-01-12 11:40 PM, Jason Wang wrote:
> 
> 
> On 2017年01月13日 10:51, John Fastabend wrote:
>> At this point the do_xdp_prog is mostly if/else branches handling
>> the different modes of virtio_net. So remove it and handle running
>> the program in the per mode handlers.
>>
>> Signed-off-by: John Fastabend <[email-masked]>
>> ---
>>   drivers/net/virtio_net.c |   76 +++++++++++++++++-----------------------------
>>   1 file changed, 28 insertions(+), 48 deletions(-)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 43cb2e0..ec54644 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -388,49 +388,6 @@ static void virtnet_xdp_xmit(struct virtnet_info *vi,
>>       virtqueue_kick(sq->vq);
>>   }
>>   
> 
> [...]
> 
>>             /* This happens when rx buffer size is underestimated */
>> @@ -598,8 +570,10 @@ static struct sk_buff *receive_mergeable(struct
>> net_device *dev,
>>           if (unlikely(hdr->hdr.gso_type))
>>               goto err_xdp;
>>   -        act = do_xdp_prog(vi, rq, xdp_prog,
>> -                  page_address(xdp_page) + offset, len);
>> +        data = page_address(xdp_page) + offset;
>> +        xdp.data = data + desc_room;
>> +        xdp.data_end = xdp.data + (len - vi->hdr_len);
> 
> It looks desc_room is always vi->hdr_len.
> 

Seems to be the case I'll just use vi->hdr_len and remove the variable.

Thanks.

>> +        act = bpf_prog_run_xdp(xdp_prog, &xdp);
>>           switch (act) {
>>           case XDP_PASS:
>>               /* We can only create skb based on xdp_page. */
>> @@ -613,13 +587,19 @@ static struct sk_buff *receive_mergeable(struct
>> net_device *dev,
>>               }
>>               break;
>>           case XDP_TX:
>> +            qp = vi->curr_queue_pairs -
>> +                vi->xdp_queue_pairs +
>> +                smp_processor_id();
>> +            virtnet_xdp_xmit(vi, rq, &vi->sq[qp], &xdp, data);
>>               ewma_pkt_len_add(&rq->mrg_avg_pkt_len, len);
>>               if (unlikely(xdp_page != page))
>>                   goto err_xdp;
>>               rcu_read_unlock();
>>               goto xdp_xmit;
>> -        case XDP_DROP:
>>           default:
>> +            bpf_warn_invalid_xdp_action(act);
>> +        case XDP_ABORTED:
>> +        case XDP_DROP:
>>               if (unlikely(xdp_page != page))
>>                   __free_pages(xdp_page, 0);
>>               ewma_pkt_len_add(&rq->mrg_avg_pkt_len, len);
>>
>