Re: [RFC Patch 0/7] kernel: Introduce multikernel architecture support

[Jan Engelhardt <ej@inai.de>]

On Friday 2025-09-19 00:25, Cong Wang wrote:

>This patch series introduces multikernel architecture support, enabling
>multiple independent kernel instances to coexist and communicate on a
>single physical machine.
>
>Each kernel instance can run on dedicated CPU
>cores while sharing the underlying hardware resources.

I initially read it in such a way that that kernels run without
supervisor, and thus necessarily cooperatively, on a system.

But then I looked at
<https://multikernel.io/assets/images/comparison-architecture-diagrams.svg>,
saw that there is a kernel on top of a kernel, to which my reactive
thought was: "well, that has been done before", e.g. User Mode Linux.
While UML does not technically talk to hardware directly, continuing
the thought "what's stopping a willing developer from giving /dev/mem
to the subordinate kernel".

On second thought, a hypervisor is just some kind of "miniature
kernel" too (if generalizing very hard).