[libvirt-users] Prevent starting a guest concurrently on multiple hosts when using shared storage

Hi list, Scenario: Libvirt managing KVM-based guests on multiple physical virtualisation hosts. These hosts are attached to some kind of shared storage, be it NFS, GFS2 or whatever. Guest images live on the shared storage so that VMs can be migrated (live or not) between the physical hosts. Basically all Libvirt hosts have definitions of all guests. How can I prevent the same guest from being started on different hosts concurrently, either by accident or intentionally? As far as I can see there is no locking or similar mechanism that would indicate to the Libvirt daemon that a guest (and its VM image) is already running on/in use by another host. This might be a very basic question but I can't seem to find a satisfying answer. Is it even possible? Or does using a shared storage mean that one has to be really, really careful what to start, and where? Is this even something for which Libvirt should be responsible? Any insight is appreciated. Thanks, Andreas