[libvirt] [PATCH] qemu: don't refuse to undefine a guest with NVRAM file

[Peter Krempa]

On Tue, Feb 24, 2015 at 15:54:24 +0000, Daniel Berrange wrote:
> On Tue, Feb 24, 2015 at 04:41:44PM +0100, Peter Krempa wrote:
> > On Tue, Feb 24, 2015 at 15:31:14 +0000, Daniel Berrange wrote:
> > > On Tue, Feb 24, 2015 at 04:23:41PM +0100, Peter Krempa wrote:
> > > > The original motivation is apparently that we should not allow anything
> > > > that would represent state of the deleted VM to be transferred
> > > > accidentaly to a new VM with same name. For the save image or snapshots
> > > > the risk of persisting any data is low as a save image would not
> > > > function without it's disk and still be somewhat secure as it would
> > > > contain the whole memory image including security. For the NVRAM though
> > > > it might uncover data stored there or even make the VM unbootable.
> > > >
> > > > I agree that the current state is not ideal as we basically force the
> > > > user to specify all the necessary flags. I think we can safely avoid
> > > > displaying the message in cases when it's not stored in the
> > > > libvirt-internal path but for the internal path I'm not convinced that
> > > > it would be a great idea to change the default.
> > > 
> > > This is the problem with trying to put this kind of policy into libvirt
> > > though. It is targetting one use case, but has forgotten other valid
> > > use cases. For example, consider if the NVRAM file or the managed save
> > > image were stored in a filesystem that was NFS. The application wishes
> > > to undefine the config on one host and define it on another host. Any
> > > checks of this kind will always be wrong for some portion of use cases.
> > 
> > The mgmt app has the option to use either non-managed save or store the
> > NVRAM in a non-default location for example ...
> 
> I remember that in the virDomainCreateFlags we have START_FORCE_BOOT
> which is defined to discard any existing managed save file.
> 
> Should we either extend that to also discard the NVRAM file, or alternatively
> add a START_RESET_NVRAM flag as a way to boot with clean BIOS ?

I'd vote for a new one. You might want to discard the save file and keep
nvram settings. The other combination will be invalid at least for qemu
as the NVRAM will be contained in the save image.

Peter
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