Subject: Re: [PATCH net 9/9] virtio-net: XDP support for small buffers

From: John Fastabend <[email-masked]>
Date: Tue, 3 Jan 2017 08:40:40 -0800

On 17-01-02 10:16 PM, Jason Wang wrote:
> 
> 
> On 2017年01月03日 06:43, John Fastabend wrote:
>> On 16-12-23 06:37 AM, Jason Wang wrote:
>>> Commit f600b6905015 ("virtio_net: Add XDP support") leaves the case of
>>> small receive buffer untouched. This will confuse the user who want to
>>> set XDP but use small buffers. Other than forbid XDP in small buffer
>>> mode, let's make it work. XDP then can only work at skb->data since
>>> virtio-net create skbs during refill, this is sub optimal which could
>>> be optimized in the future.
>>>
>>> Cc: John Fastabend <[email-masked]>
>>> Signed-off-by: Jason Wang <[email-masked]>
>>> ---
>>>   drivers/net/virtio_net.c | 112 ++++++++++++++++++++++++++++++++++++-----------
>>>   1 file changed, 87 insertions(+), 25 deletions(-)
>>>
>> Hi Jason,
>>
>> I was doing some more testing on this what do you think about doing this
>> so that free_unused_bufs() handles the buffer free with dev_kfree_skb()
>> instead of put_page in small receive mode. Seems more correct to me.
>>
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index 783e842..27ff76c 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -1898,6 +1898,10 @@ static void free_receive_page_frags(struct virtnet_info
>> *vi)
>>
>>   static bool is_xdp_queue(struct virtnet_info *vi, int q)
>>   {
>> +       /* For small receive mode always use kfree_skb variants */
>> +       if (!vi->mergeable_rx_bufs)
>> +               return false;
>> +
>>          if (q < (vi->curr_queue_pairs - vi->xdp_queue_pairs))
>>                  return false;
>>          else if (q < vi->curr_queue_pairs)
>>
>>
>> patch is untested just spotted doing code review.
>>
>> Thanks,
>> John
> 
> We probably need a better name for this function.
> 
> Acked-by: Jason Wang <[email-masked]>
> 

How about is_xdp_raw_buffer_queue()?

I'll submit a proper patch today.
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