One of the interesting architectural changes in Hyper-V 2012 Server is the boot order. In Windows Server 2008, first booted partition was the OS in parent partition. After booting partition it was launching Hypervisor using hvboot.sys.
hvboot.sys was performing following actions:
- Detects whether a hypervisor is already loaded or not
- Determines processor if it is Intel or AMD
- Loads hypervisor image
- Invokes hypervisor launch code
- virtual processor is created
In Windows Server 2012 and Windows 8, now it does early launch of hypervisor before OS and applies microcode updates needed. Therefore OS in the parent partition is booted on a Virtul Processor.
This change also allows you to be able to manage more than 64VPs.