[ovs-dev] [dpdk.org代发][dpdk-dev] Question about using virtio_user in OVS-DPDK

William Tu u9012063 at gmail.com
Thu Jan 2 20:01:55 UTC 2020

On Wed, Jan 1, 2020 at 5:05 PM Yi Yang (杨燚)-云服务集团 <yangyi01 at inspur.com> wrote:
> William, use the below option for your tap0
> sudo ovs-vsctl add-port br-int virtio_user0 -- set Interface virtio_user0 type=dpdk options:dpdk-devargs=net_virtio_user0,iface=tap0,path=/dev/vhost-net,queue_size=1024
> vistio_user also can create tap0 if it doesn't exist, you remove "iface=tap0" from option for that case.
> Maybe ovs port name can't be same as tap interface names, it is just my guess.

Hi Yi,

Thanks for your reply. I'm using this ovs command
ovs-vsctl add-port br0 virtio_user0 -- set Interface virtio_user0 type=dpdk \
    options:n_rxq=1 options:n_txq=1 \

I hit an error showing
'net_virtio_user0,iface=tap0,path=/dev/vhost-net, queues=1' attached
|00058|netdev_dpdk|DBG|Port virtio_user0: Requesting a mempool of
262144 mbufs of size 2176 on socket 0 for 1 Rx and 2 Tx queues, cache
line size of 64
00060|netdev_dpdk|WARN|Rx checksum offload is not supported on port 0
00061|dpdk|ERR|virtio_dev_configure(): Unsupported Rx multi queue mode 1
00062|dpdk|ERR|Port0 dev_configure = -22
00063|netdev_dpdk|WARN|Interface virtio_user0 eth_dev setup error
Invalid argument
00064|netdev_dpdk|ERR|Interface virtio_user0(rxq:1 txq:1 lsc interrupt
mode:false) configure error: Invalid argument

"Unsupported Rx multi queue mode 1" at virtio_dev_configure()
    if (rxmode->mq_mode != ETH_MQ_RX_NONE) {
            "Unsupported Rx multi queue mode %d",
//      return -EINVAL;
Based on DPDK master
commit 2e088e6f94b773233c06440763c1be43d0d705b3

Skipping it seems to work, but I don't understand how to set virtio_user
to disable mq_mode in virtio_dev.  For virtio user, there are these parameters:

    "path=<path> "
    "mac=<mac addr> "
    "cq=<int> "
    "queue_size=<int> "
    "queues=<int> "
    "iface=<string> "
    "server=<0|1> "
    "mrg_rxbuf=<0|1> "
    "in_order=<0|1> "


> -----邮件原件-----
> 发件人: dev [mailto:dev-bounces at dpdk.org] 代表 William Tu
> 发送时间: 2020年1月1日 6:19
> 收件人: <dev at openvswitch.org> <dev at openvswitch.org>; dev at dpdk.org
> 抄送: Jianfeng Tan <jianfeng.tan at linux.alibaba.com>
> 主题: [dpdk.org代发][dpdk-dev] Question about using virtio_user in OVS-DPDK
> Hi,
> I'm trying to find a faster way to communicate from userspace OVS to kernel. So I create a virtio_user port at OVS-DPDK, and send packets to kernel's tap device.
> packets in OVS userspace -> virtio-user port -> vhost-net (kernel) -> tap device (kernel) As described in paper[1], figure 1 for legacy applications.
> But there is no documentation about it. I tried:
> 1) load vhost-net
> # lsmod | grep vhost
> vhost_net              32768  0
> vhost                  57344  1 vhost_net
> tap                    28672  1 vhost_net
> tun                    57344  8 vhost_net
> 2) start OVS
> 3) create tap and attach to OVS
> ip tuntap add mode tap tap0
> ip link set dev tap0 up
> ovs-vsctl add-port br0 tap0 -- set interface tap0 type=dpdk \
>     options:dpdk-devargs=vdev:net_virtio_user1,iface=tap0,path=/dev/vhost-net
> So I thought this is a faster channel using virtio ring than readv/writev to the tap fd.
> But it doesn't work.
> 2019-12-31T22:06:39.956Z|00033|netdev|WARN|could not create netdev
> tap0 of unknown type dpdk
> 2019-12-31T22:06:39.956Z|00034|bridge|WARN|could not open network device tap0 (Address family not supported by protocol)
> Any suggestions? Or do I understand the concept of virtio_user correctly?
> [1] VIRTIO-USER: A New Versatile Channel for Kernel-Bypass Networks Thanks William

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