Subject: Re: [PATCH net] macvtap: unbreak receiving of gro skb with frag list

From: Jason Wang <[email-masked]>
Date: Mon, 26 Oct 2015 14:53:38 +0800

On 10/26/2015 02:09 PM, Michael S. Tsirkin wrote:
> On Mon, Oct 26, 2015 at 11:15:57AM +0800, Jason Wang wrote:
>>
>> On 10/23/2015 09:37 PM, Michael S. Tsirkin wrote:
>>> On Fri, Oct 23, 2015 at 12:57:05AM -0400, Jason Wang wrote:
>>>> We don't have fraglist support in TAP_FEATURES. This will lead
>>>> software segmentation of gro skb with frag list. Fixes by having
>>>> frag list support in TAP_FEATURES.
>>>>
>>>> With this patch single session of netperf receiving were restored from
>>>> about 5Gb/s to about 12Gb/s on mlx4.
>>>>
>>>> Fixes a567dd6252 ("macvtap: simplify usage of tap_features")
>>>> Cc: Vlad Yasevich <[email-masked]>
>>>> Cc: Michael S. Tsirkin <[email-masked]>
>>>> Signed-off-by: Jason Wang <[email-masked]>
>>> Thanks!
>>> Does this mean we should look at re-adding NETIF_F_FRAGLIST
>>> to virtio-net as well?
>> Not sure I get the point, but probably not. This is for receiving and
>> skb_copy_datagram_iter() can deal with frag list.
>
> Point is:
> - bridge within guest
> - assigned device creating gro skbs with frag list bridged to virtio

I see, but this problem looks not specific to virtio. Most cards does
not support frag list.