"Currently the mainline Linux kernel doesn't allow serving as the root partition on the Microsoft Hypervisor, but that is what Microsoft is wanting to change.
The virtualization stack in the root partition provides a memory manager for virtual machines, management APIs, and virtualized I/O devices.
Microsoft's Hyper-V architecture documentation describes the root partition concept as "the hypervisor virtualizes processors and memory and provides mechanisms for the virtualization stack in the root partition to manage child partitions (virtual machines) and expose services such as I/O devices to the virtual machines.
While Linux already supports Hyper-V and in fact 50% or more of the VMs on Azure are Linux-based , what Microsoft is working on now is looking to add Linux root partition support with the Microsoft Hypervisor.The root partition in the context of the Microsoft Hypervisor is similar to Xeon's Dom0 that is used for starting and managing the unprivileged domains in turn.
Microsoft engineers are sending out new kernel patches in looking to expand the Linux support around the Microsoft Hypervisor (Hyper-V).