Scheduling with Device Capabilities

In order to be able to schedule an instance with specific resources
AND capabilities, the info about the available resources and
capabilities needs to be available to the Nova scheduler.

The resource provider blueprint[2] provides the framework for handling
quantitative resources in the request spec and facilitates the
optimization of the overall scheduling process by allowing for a rough
initial filtering. However, today, there is no clear guidelines as to
where to store qualitative capabilities. Current status is that Nova
keeps CPU info under cpu_info column, but other compute related
resource such as the PCI devices and their capabilities (such as
device type, vendor ID, product ID) are kept in a separate table
(pci_devices table).

This make it very hard to add additional device and capabilities.

This blueprint address the qualitative (i.e capabilities) part of the request
spec and how to easily extend nova for adding new device with capabilities.