Kernel: Introduce Multikernel Architecture Support

Sounds similar to CoLinux where you could run a "cooperative Linux" alongside Windows http://www.colinux.org/

This was underrated!

HP printers are similar. They run Linux on two cores and an RTOS on the other.

IIRC, colinux is similar to user mode Linux, which boots a kernel in userland. That is, the kernel runs under windows as an application rather than alongside it.

Relatively common in more powerful embedded systems. See for example https://www.openampproject.org/ which is a framework for running multiple cores of Linux, baremtal, or an RTOS together.

It says on the web page I linked that:

Unlike in other Linux virtualization solutions such as User Mode Linux (or the forementioned VMware), special driver software on the host operating system is used to execute the coLinux kernel in a privileged mode (known as ring 0 or supervisor mode).

By constantly switching the machine's state between the host OS state and and the coLinux kernel state, coLinux is given full control of the physical machine's MMU (i.e, paging and protection) in its own specially allocated address space, and is able to act just like a native kernel, achieving almost the same performance and functionality that can be expected from a regular Linux which could have ran on the same machine standalone.

So my understanding is that it's a Windows driver which contains a full Linux kernel and does some (scary sounding!) time sharing with the Windows kernel running at the same CPL.