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Re: [libvirt] Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor device

From: Daniel P. Berrange
Subject: Re: [libvirt] Re: [Qemu-devel] [PATCH 1/6] Allow multiple monitor devices (v2)
Date: Tue, 14 Apr 2009 10:17:26 +0100
User-agent: Mutt/1.4.1i

On Tue, Apr 14, 2009 at 12:15:23PM +0300, Avi Kivity wrote:
> 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.

That is true, but we'd still be considering direct monitor access to
be a 'expert' user mode of use. If they wish to shoot themselves in
the foot by triggering a migration at same time they are hotplugging
I'm fine if their whole leg gets blown away.  

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