[dpdk-dev] KNI as kernel vHost backend failing

[Xie, Huawei]

On 1/1/2015 5:02 PM, sai kiran wrote:
> Hi,
>
>
>
> We are trying to experiment with DPDK’s KNI application, with KNI working
> as Kernel vHost backend.
>
>
> 1.  After starting the KNI application, KNI application has detected link
> up.
>
>
> *[root at localhost kni]# ./build/app/kni -c 0xf0 -n 4 -- -p 0x3 -P
> --config="(0,4,6),(1,5,7)"*
>
>
> APP: Initialising port 0 ...
>
> KNI: pci: 10:00:01       8086:10fb
>
> APP: Initialising port 1 ...
>
> PMD: To improve 1G driver performance, consider setting the TX WTHRESH
> value to 4, 8, or 16.
>
> KNI: pci: 16:00:01       8086:10e7
>
> Checking link status
>
> .................................done
>
> Port 0 Link Up - speed 10000 Mbps - full-duplex
>
> Port 1 Link Up - speed 1000 Mbps - full-duplex
>
> APP: Lcore 5 is reading from port 1
>
> APP: Lcore 7 is writing to port 1
>
> APP: Lcore 6 is writing to port 0
>
> APP: Lcore 4 is reading from port 0
>
>
> 2. As mentioned in Programming guide, *sock_en* variable in sysfs is
> enabled and a fd is generated
>
> [root at localhost dpdk-1.7.1]# cat /sys/class/net/vEth0/sock_en
> 1
> [root at localhost dpdk-1.7.1]# cat /sys/class/net/vEth1/sock_en
> 1
> [root at localhost dpdk-1.7.1]# cat /sys/class/net/vEth0/sock_fd
> 11
> [root at localhost dpdk-1.7.1]# cat /sys/class/net/vEth1/sock_fd
> 12
>
> 3. But when a VM is launched with this file-descriptor as the
> vhost-backend, the qemu-kvm is throwing an ioctl-failure error. This
> ioctl
> is making the vhost-backend fallback to virtio-userspace.
>
>
>
> [root at localhost qemu-kvm-1.2.0]# /usr/bin/qemu-kvm -m 2048 -enable-kvm
> -cpu
> host -smp 2 -name VSK1 -drive file=/root/SAI/NSVPX-KVM-11.0-28.1_nc.raw
> -netdev tap,fd=12,id=mynet_kni,vhost=on -device
> virtio-net-pci,netdev=mynet_kni,bus=pci.0,addr=0x4,ioeventfd=on
>
> qemu-kvm: -netdev tap,fd=12,id=mynet_kni,vhost=on: TUNGETIFF ioctl()
> failed: Bad file descriptor
>
> TUNSETOFFLOAD ioctl() failed: Bad file descriptor
>
> qemu-kvm: unable to start vhost net: 88: falling back on userspace virtio
>
> qemu-kvm: unable to start vhost net: 88: falling back on userspace virtio
>
> qemu-kvm: unable to start vhost net: 88: falling back on userspace virtio
>
> With this failure, the traffic from VM is not flowing through KNI
> interface.
>
>
>
> The above mentioned ioctl failure does NOT happen consistently. During
> the
> instances when failure is not seen, traffic flows successfully through
> the
> KNI interfaces.
>
>
>
> Can someone please shed some light as to what is happening in this case.
> Are we missing something here? Is there a known issue?
>
>
Hi Kiran:
Is it possible you switch to user space vhost?
>
> Thanks,
>
> Kiran
>
>
>