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


From: Marcel Apfelbaum
Subject: Re: [Qemu-devel] [RFC 0/1] Add live migration support to the PVRDMA device
Date: Tue, 25 Jun 2019 11:49:33 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1

Hi Dmitry,

On 6/25/19 11:39 AM, Dmitry Fleytman wrote:

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?

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


[...]




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