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

[Dmitry Fleytman]

> On 25 Jun 2019, at 11:14, Marcel Apfelbaum <address@hidden> 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?

Do you see any outgoing packets in the sniffer?

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