Re: [dpdk-dev] [PATCH] vhost: support UDP Fragmentation Offload

["Hu, Jiayu" <jiayu.hu@intel.com>]

Hi Stephen,

> -----Original Message-----
> From: Stephen Hemminger [mailto:stephen@networkplumber.org]
> Sent: Tuesday, November 21, 2017 3:13 PM
> To: Hu, Jiayu <jiayu.hu@intel.com>
> Cc: dev@dpdk.org; yliu@fridaylinux.org; Tan, Jianfeng
> <jianfeng.tan@intel.com>
> Subject: Re: [dpdk-dev] [PATCH] vhost: support UDP Fragmentation Offload
> 
> On Tue, 21 Nov 2017 14:56:52 +0800
> Jiayu Hu <jiayu.hu@intel.com> wrote:
> 
> > In virtio, UDP Fragmentation Offload (UFO) includes two parts: host UFO
> > and guest UFO. Guest UFO means the frontend can receive large UDP
> packets,
> > and host UFO means the backend can receive large UDP packets. This patch
> > supports host UFO and guest UFO for vhost-user.
> >
> > Signed-off-by: Jiayu Hu <jiayu.hu@intel.com>
> 
> This may no longer be a desirable feature to implement.
> UFO was just deprecated and removed from Linux.
> It had no useful benefit.

The main reason of supporting UFO is to make the backend live migration from
vhost-net to vhost-user possible. Host and guest UFO are default features for virtio-net,
and vhost-net supports both. But vhosy-user doesn't support them. If we want to
migrate from vhost-net to vhost-user, this features gap would cause live migration fail.

Thanks,
Jiayu