[dpdk-dev] Why the offloads of the guest's virtio-net network adapter are disabled when vhost-user is used?

[Liu, Jijiang]

> -----Original Message-----
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Tetsuya Mukawa
> Sent: Tuesday, August 25, 2015 11:23 AM
> To: leo zhu; dev at dpdk.org
> Subject: Re: [dpdk-dev] Why the offloads of the guest's virtio-net network
> adapter are disabled when vhost-user is used?
> 
> On 2015/08/24 22:09, leo zhu wrote:
> > Hi all,
> >
> > I am running the vhost sample application on my server.
> >
> > According to the dpdk-sample-applications-user-guide.pdf, I run the
> > Virtual Machine with vhost-user enabled.
> > Following is the command that is used to run the virtual machine.
> >
> >
> >
> >
> >
> >
> > *qemu-system-x86_64 /root/leo/ubuntu-1.img -enable-kvm -m 1024 -
> vnc :5
> > -chardev
> > \socket,id=char1,path=/root/leo/dpdk-2.0.0/examples/vhost/usvhost
> > -netdev type=vhost-user, \id=mynet1,chardev=char1,vhostforce -device
> > virtio-net-pci,mac=00:00:00:00:00:01,netdev=mynet1 \-object
> > memory-backend-file,id=mem,size=1024M,mem-
> path=/dev/hugepages,share=on
> > -numa node,memdev=mem -mem-prealloc*
> >
> > After the Virtual Machine is started, I found the offloads of the
> > Virtual Machine's virtio-net network adapter are all disabled*.* The
> > offloads status is checked with command* ethtool -k eth0*. I try to
> > enables the offloads with ethtool command, but it does not work.
> >
> > My questions are:
> >
> > 1. Can the offloads of the guest's virtio-net network adapter be
> > enabled when vhost-user is used?
> 
> Hi Leo,
> 
> I guess we need additional implementations in librte_vhost to enable
> offloads.
> 
> 
> > 2. If the offloads can't be enabled when vhost-user is used, what is the
> reason?
> 
> Features are negotiated not olny between virtio-net driver on guest and
> virtio-net device in QEMU, but also virtio-net device in QEMU and vhost-user
> backend in librte_vhost.
> As a result, if vhost-user backend doesn't support some features, virtio-net
> driver on guest also cannot use them.
> 
> Please see "lib/librte_vhost/virtio-net.c"
Yes, you are correct.

I'm working on the vhost TSO offload,  the offload set in struct 'virtio_net_hdr' need to be considered in both virtio-net and vhost side. 

> /* Features supported by this lib. */
> #define VHOST_SUPPORTED_FEATURES ((1ULL <<
> VIRTIO_NET_F_MRG_RXBUF) | \
>                                 (1ULL << VIRTIO_NET_F_CTRL_VQ) | \
>                                 (1ULL << VIRTIO_NET_F_CTRL_RX) | \
>                                 (1ULL << VHOST_F_LOG_ALL))
> 
> This is all current librte_vhost supports.
> 
> Thanks,
> Tetsuya
> 
> > It will be great if someone from the forum could give the answers and clues.
> >
> > Thanks.
> > Leo