[libvirt] Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2)

Avi Kivity avi at redhat.com
Tue Apr 14 09:15:23 UTC 2009

Daniel P. Berrange wrote:
> Yes indeed its a little crazy :-)  As anthony mentioned if libvirt were 
> able to be notified of changes a user makes in the monitor, there's no 
> reason we could not allow end users to access the monitor of a VM 
> libvirt is managing. We just need to make sure libvirt doesn't miss
> changes like attaching or detaching block devices, etc, because that'll
> cause crash/data loss later when libvirt migrates or does save/restore,
> etc because it'll launch QEMU with wrong args

You still have an inherent race here.

user: plug in disk
libvirt: start migration, still without disk
qemu: libvirt, a disk has been plugged in.

>> I don't see how adding those low-level monitory things to libvirt is
>> an improvement - debugging and scripted keystrokes are not the sort of
>> functionality libvirt is for - or is it?
> I think it could probably be argued that sending fake keystrokes could
> be within scope. Random ad-hoc debugging probably out of scope.

That means that to debug a problem in the field you have to locate a 
guest's host, and follow it around as it migrates (or disable migration).

I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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