Re: [Qemu-devel] [RFC 0/1] Add live migration support to the PVRDMA device

[Marcel Apfelbaum <marcel.apfelbaum@gmail.com>]

Hi Dmitry,

On 6/25/19 11:39 AM, Dmitry Fleytman wrote:
>
>> On 25 Jun 2019, at 11:14, Marcel Apfelbaum <marcel.apfelbaum@gmail.com> wrote:
>>
>> Hi Sukrit
>>
>> On 6/21/19 5:45 PM, Sukrit Bhatnagar wrote:
>>> Hi,
>> [...]
>>> This RFC is meant to request suggestions on the things which are
>>> working and for help on the things which are not.
>>>
>> [...]
>>> What is not working:
>>>
>> [...]
>>> * It seems that vmxnet3 migration itself is not working properly, at least
>>>    for me. The pvrdma device depends on it, vmxnet3 is function 0 and pvrdma
>>>    is function 1. This is happening even for a build of unmodified code from
>>>    the master branch.
>>>    After migration, the network connectivity is lost at destination.
>>>    Things are fine at the source before migration.
>>>    This is the command I am using at src:
>>>
>>>    sudo /home/skrtbhtngr/qemu/build/x86_64-softmmu/qemu-system-x86_64 \
>>>      -enable-kvm \
>>>      -m 2G -smp cpus=2 \
>>>      -hda /home/skrtbhtngr/fedora.img \
>>>      -netdev tap,id=hostnet0 \
>>>      -device vmxnet3,netdev=hostnet0,id=net0,mac=52:54:00:99:ff:bc \
>>>      -monitor telnet:127.0.0.1:4444,server,nowait \
>>>      -trace events=/home/skrtbhtngr/trace-events \
>>>      -vnc 0.0.0.0:0
>>>
>>>    Similar command is used for the dest. Currently, I am trying
>>>    same-host migration for testing purpose, without the pvrdma device.
>>>    Two tap interfaces, for src and dest were created successfully at
>>>    the host. Kernel logs:
>>>    ...
>>>    br0: port 2(tap0) entered forwarding state
>>>    ...
>>>    br0: port 3(tap1) entered forwarding state
>>>
>>>    tcpdump at the dest reports only outgoing ARP packets, which ask
>>>    for gateway: "ARP, Request who-has _gateway tell guest1".
>>>
>>>    Tried using user (slirp) as the network backend, but no luck.
>>>       Also tried git bisect to find the issue using a working commit (given
>>>    by Marcel), but it turns out that it is very old and I faced build
>>>    errors one after another.
>>>
>>>    Please note that e1000 live migration is working fine in the same setup.
>>>
>> I tried to git bisect , but I couldn't find a working version of vmxnet supporting live migration ....
>> I tried even a commit from December 2014 and it didn't work.
>>
>> What is strange (to me) is that the networking packets can't be sent from the guest (after migration)
>> even after rebooting the guest.
> This makes me think that some network offload configuration wasn’t properly migrated or applied.
> What network backend are you using?

Suktrit tried with tap device, I tried with slirp.
If you can point me to the property that disables all the offloads it 
will really help.

> Do you see any outgoing packets in the sniffer?

I didn't use the sniffer, I checked dmesg in guest, there was a line 
complaining that it can't send packets.

Thanks,
Marcel

>> Any help or pointer would be greatly appreciated.
>> Thanks,
>> Marcel
>>
>>
>> [...]