[Libvirt-cim] [RFC] override CreateSnapshot extrinsic

[Jim Fehlig]

Since the CreateSnapshot() extrinsic has 2 vendor defined values added 
for SnapshotType parameter, I think the method should be overridden to 
define these new values.  The attached patch does so by creating a new 
class Virt_VirtualSystemSnapshotService where CreateSnapshot is 
overridden.  The various virtualizer flavors then inherit from 
Virt_VirtualSystemSnapshotService instead of 
CIM_VirtualSystemSnapshotService directly.

Some tools will parse the class info and format gui based on qualifiers 
it finds.  In the case of CreateSnapshot, such tools will not display 
the vendor additions unless we override the method and describe the 
additions.

While on the subject, I would like to understand the usefulness of 
SnapshotType 32768.  This type will save the vm's memory state and 
subsequently restore the vm.  IMO applying this memory snapshot later 
would be quite dangerous.  The vm has since been running and the disk 
state will be quite different from when the memory snapshot was taken.  
Does this make sense or am I not thinking clearly :-)?

Finally, invoking CreateSnapshot with SnapshotType 32769 will save the 
vm and leave it powered off.  Querying EnabledState shows the vm 
'Enabled but Offline' (suspended).  According to System Virtualization 
Profile, one should be able to move a vm in this state to Enabled by 
invoking RSC(Enabled) but doing so results in "snapshot exists, apply 
snapshot" error.  So the behavior diverges from the spec IMO.  It seems 
the current behavior of SnapshotService should just be implemented via 
RSC.  CreateSnapshot -> RSC(Enabled but Offline), ApplySnapshot -> 
RSC(Enabled)

Regards,
Jim


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