Microsoft engineer Wei Liu sent out a series of kernel patches to Linux’s Hyper-V code. The new “request for comment” (RFC) patches aims to make Linux run as a root partition (like Xen’s Dom0) on Microsoft Hypervisor (Hyper-V).
For those who don’t know, Hyper-V is a very well-known virtualization technology by Microsoft that specifically provides hardware virtualization. Hyper-V not only lets you create virtual hard drives and network switches but also runs multiple virtual operating systems on the Windows platform.
Even Linux already supports Hyper-V and half or more virtual machines on Microsoft’s Azure cloud platform are Linux-based. However, the current mainline Linux kernel does not allow it to run as the root partition on the Microsoft Hypervisor.
Hence, Microsoft now wants to create a complete virtualization stack with Linux by introducing Linux root partition support for its Hyper-V.
As Microsoft’s Hyper-V architecture documentation describes that the root partition owns and has direct access to physical I/O devices, the virtualization stack in the root partition provides a memory manager for virtual machines, management APIs, and virtualized I/O devices.
Wei Liu also added that the root partition for Microsoft Hypervisor is inspired by Domain 0 (Dom0) of open source and type-1 hypervisor, Xen, which contains the toolstack and drivers for the hardware to control virtual machines.
Additionally, Microsoft engineers have also ported open source Virtual Machine Monitor (VMM) Cloud Hypervisor, which is already being tested by them to boot a Linux guest with Virtio devices.
As of now, the patch series only implements absolutely necessary components to get things running. Therefore, more subsequent codes are yet to come that will provide a device node (/dev/mshv) such that userspace programs can create and run virtual machines.