Resend because I forgot the [nova] in subject.

        There are some discussion and disagreement on the requirement from 
flavor and image metadata at nova spec 
and I want to get more input from the community. 
        When launch a VM, some requirements may come from image metadata and 
flavor. There are a lot of such cases like serial_port_count, memory_pagesize, 
hw_numa_nodes, hw:cpu_max_sockets etc. Most of them are done in 

        Both the nova-spec and the current implementation seems agree that if 
flavor has the requirement, the image's metadata should not require more than 
the flavor requirement.

        However, the disagreement comes when no requirement from flavor, i.e. 
only image has the resource requirement. For example, for serial_port_count, 
"If flavor extra specs is not set, then any image meta value is permitted". For 
hw_mem_page_size, it's forbidden if only image request and no flavor request 
( ), 
and hw_numa_nodes will fail if both flavor and image metadata are specified 
( ). 

        As to this nova spec at , 
someone (Don, Malini) think if image requires some feature/resource that is not 
specified in flavor, it should be ok, while I think it should be forbidden.

        I discussed with Jay Pipe on IRC before and he thought if flavor has no 
requirement, image requirement should be failed, and I created a bug at at that time.  But according to 
the discussion on this BP, seems this is not always accepted by others.

        I hope to get feedback from the mailing list on the relationship of 
requirement from image/flavor. Possibly we should take different policy for 
different resource requirement, but some general rule and the reason for those 
rules will be helpful.


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