Bug in lifecycle management start wrt suspended VMs

["Daniel P. Berrange" <berrange@redhat.com>]

With the lifecycle patches that were recently added, XenD now keeps track
of suspended domains automatically. It does not, however, stop you from
shooting yourself in the foot. eg, if you suspend a domain 'foo', it'll
quite happily let you then start it, use it for a while, shut it down,
and then restore the original state file.  This will likely trash the
filesystem of the guest. What's worse is that 'xm list' does not provide
any visual distinction between shutoff & suspended guests, so you can't
tell if there's a suspended image lying around on disk.

In essence it was possible for me to do the following sequence:

    xm create demo
    xm start demo
    xm suspend demo
    xm start demo
    xm shutdown demo
    xm resume demo

I'd suggest that the 4th command 'xm start' should not be allowed to
succeed given that there is a saved VM image for demo there from step 3.

Of course we would still need a way to recover from situation where
a resume failed - some way to explicitly blow away the saved image
and start from fresh. Perhaps  'xm start --force demo' could be used
to get rid of any state file from a suspended VM in this case ?

Regards,
Dan.
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