[pve-devel] livemigration problem with usb-tablet (crashs)

Alexandre DERUMIER aderumier at odiso.com
Tue Feb 28 11:47:14 CET 2012

Hi Dietmar,

User reports some problem with live migration when usb tablet is present.


I have tested it myself, depend of the guest os, you can have crash of the vm if you move mouse after live migration.

I see some users reports on qemu mailing list, I have send mail to redhat developper which maintain the usb, but don't have receive response yet.
I think the usb part of qemu is a little broken for the moment ;)

I have a workaround for it:

1) unplug usb tablet before migration

2) then re-add it after the migration.

What do you think about it ?

1) is easy, just a qm monitor before doing migration on the source host.

2) not so easy, I'll try to readd device in at the end of vm_start, but it's not working.(too early, I think the target vm is not yet migrate).
   So I have read the code, I think It could be done at migration phase3,from the host,so we are sure that migration is done.
   But I need to send a qemu monitor command from source host to target host. (And I don't know....)

   Other possiblity, is to plug the tablet when connecting to console for the first time.
   But I need also to send qemu monitor command to a remote host, if the vm is not on the same server that the pve-manager.

   Can I use something like 'ssh targethost -> qm monitor XXX sendmonitorcommand" ?

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