[Xen-devel] Reverse migration breaks/freezes VM

["Rustedt, Florian" <Florian.Rustedt@xxxxxxxxxxx>]

Hello list,

I've got strange phenomenons with migrations. I think it's a bug, but am not 
sure, so i am asking for your help to find this ou, please ;)

First the construct:
Two HP DL180G5(xen0,xen1) with dual-quadcore each, 8G RAM.

On each a dom0 with selfcompiled(because of network drivers) 
gentoo-sources-xen-2.6.27_amd64 and Xen 3.3.0. The installation is completely 
the same (rsynct), only different in ip and hostname.

Both share a drbd0(v8.3.0) device. On it an lvm with one lv per vm.

Now what's the problem:

If i migrate a running vm(mx1-smartnet-de) from xen0 to xen1, it seems to work.
I could do a "xm migrate mx1-smartnet-de xen1" without any interuption while 
having a ssh-connection to the vm and downloading a kernel-source in it.

Then i did a "xm migrate mx1-smartnet-de xen0" on xen1 to move it back again. 
After that, the vm freezes at 100%CPU and that's it! Can't connect to it any 
more, whether via ssh nor via vnc/fb or console. Only "xm destroy" could help, 
"xm shutdown" has no impact.

For debugging, i added the concerning parts of the xend.log from each and the 
kernel-configs, so that you could try to help me find the prob perhaps in the 
logs?

Just after having started the vm: 
xen0_after_start_of_vm.log

Then after the first migration:
xen0_after_migrate_to_xen1_of_vm.log
xen1_after_migrate_to_xen1_of_vm.log

And last, after the reverse:
xen0_after_migrate_back_from_xen1_of_vm.log
xen1_after_migrate_back_from_xen1_of_vm.log

I don't believe it is a drbd/lvm problem, because drbd keeps in "0: 
cs:Connected ro:Primary/Primary ds:UpToDate/UpToDate C r---" and there are no 
lv-concerning log-entries in syslog.

There are of course errors concerning "retry suspend domain failed", but 
there's no hint, WHY this has got failed?

Kind regards, Florian
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Attachment: xen1_after_migrate_to_xen1_of_vm.log
Description: xen1_after_migrate_to_xen1_of_vm.log

Attachment: xen0_after_migrate_back_from_xen1_of_vm.log
Description: xen0_after_migrate_back_from_xen1_of_vm.log

Attachment: xen0_after_migrate_to_xen1_of_vm.log
Description: xen0_after_migrate_to_xen1_of_vm.log

Attachment: xen0_after_start_of_vm.log
Description: xen0_after_start_of_vm.log

Attachment: xen1_after_migrate_back_from_xen1_of_vm.log
Description: xen1_after_migrate_back_from_xen1_of_vm.log

Attachment: config-2.6.27-xen-r5_DOMU
Description: config-2.6.27-xen-r5_DOMU

Attachment: config-2.6.27-xen-r5_DOM0
Description: config-2.6.27-xen-r5_DOM0

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