[Libvir] RFC: requesting APIs for host physical resource discovery

[Daniel P. Berrange]

The current libvirt APIs allow the host's physical resources to be split up
and allocated to guest domains, however, there is no way to discover what
the available host resources actually are. Thus I would like to suggest the
inclusion of new APIs to enable host resource discovery. As a starting point
I'd like to be able to query the following information:

  * Number of physical CPUs - ability to enumerate the CPUs in the host,
    both those currently present, and theoretical maximum (to take account
    of hotplug). 
  * Amount of RAM  - actual physical RAM present, and that available for
    guest usage (eg discounting that reserved by a hypervisor or equiv)
  * CPU relationship - ie ability to distinguish between CPUs which
    are hyperthread siblings, on same core, or on separate sockets

Alonside these basic queries it would be desirable to add a further resource
resource management API to allow for setting of a guest domain's CPU affinity.
ie ability control what CPUs the VMM is allowed to schedule a domain on.

Once this first basic set of caapbilties for resource discovery are provided
for, then I believe it will be neccessary to provide some more advanced 
queries, in particular:

  * NUMA topology - ability to enumerate NUMA nodes, the CPUs associated
    with each node & the RAM range mapped to that node

Regards,
Dan.
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