Re: [virtio-dev] [PATCH v4] content: Introduce VIRTIO_NET_F_STANDBY feature

[Sameeh Jubran <sameeh@daynix.com>]

On Wed, Nov 21, 2018 at 8:41 PM Michael S. Tsirkin <mst@redhat.com> wrote:
>
> Great to see you making progress on this!
> Some comments below:
>
> On Wed, Nov 21, 2018 at 05:39:38PM +0200, Sameeh Jubran wrote:
> > I have created a setup which has two hosts (host A and host B) with X710 10G
> > cards connected back to back. On one host (I'll refer to this host as host A) I
> > have configured a bridge with the PF interface as well as vitio-net's interface
> > (standby) both attached to it.
>
> ...
>
> > The command line I used:
> >
> > /root/qemu/x86_64-softmmu/qemu-system-x86_64 \
> > -netdev tap,id=hostnet0,script=world_bridge_standalone.sh,downscript=no,ifname=
> > cc17 \
> > -device e1000,netdev=hostnet0,mac=56:cc:c1:01:cc:21,id=cc17 \
>
> What's e1000 doing here?
> Can this be reason you can not talk to host?
I don't think so, the e1000 is for enabling WAN connection on the
guest for downloading packages and ssh connection. It is connected to
a separate bridge which is connected to the external interface of the
host.
>
> > -netdev tap,vhost=on,id=hostnet1,script=test_bridge_standalone.sh,downscript=
> > no,ifname=cc1_72,queues=4 \
> > -device virtio-net,host_mtu=1500,netdev=hostnet1,mac=8a:f7:20:29:3b:cb,id=
> > cc1_72,vectors=10,mq=on,primary=cc1_71 \
> > -device vfio-pci,host=65:02.1,id=cc1_71,standby=cc1_72 \
> > -enable-kvm \
> > -name netkvm \
> > -m 3000M \
> > -drive file=/dev/shm/fedora_29.qcow2,if=ide,id=drivex \
> > -smp 4 \
> > -vga qxl \
> > -spice port=6110,disable-ticketing \
> > -device virtio-serial-pci,id=virtio-serial0,max_ports=16,bus=pci.0,addr=0x7 \
> > -chardev spicevmc,name=vdagent,id=vdagent \
> > -device virtserialport,nr=1,bus=virtio-serial0.0,chardev=vdagent,name=
> > com.redhat.spice.0 \
> > -chardev socket,path=/tmp/qga.sock,server,nowait,id=qga0 \
> > -device virtio-serial \
> > -device virtserialport,chardev=qga0,name=org.qemu.guest_agent.0 \
> > -monitor stdio
>
>
> ...
>
> > Since I couldn't ping from VM to host B, I did an iperf test between the VM and
> > host A with the feature enabled and during the test I have unplugged the sriov
> > device, the device was unplugged successfully and no drops where observed as
> > you can see in the results below:
> >
> > [root@dhcp156-44 ~]# ifconfig
>
> Well I suspect this won't tell you anything, this shows packet drops at
> the hardware level. When e.g. link is down linux won't send any packets
> out. The simplest test is to monitor latency and throughput and see that
> while it is lower for the duration of migration, there are no huge
> spikes around the switch.
Oh, okay will do that.

I have noticed some nasty lag when I tried to ssh to the VM using the
failover interface while I didn't experience that with the e1000.
Sridhar Any idea what might be the cause?
>
> --
> MST



-- 
Respectfully,
Sameeh Jubran
Linkedin
Software Engineer @ Daynix.