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

[Avi Kivity <avi redhat com>]

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.