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

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Message-ID: <3ns36rp5-rp37-1nns-9q43-op05or6s26nq@vanv.qr>
Date: Sun, 21 Sep 2025 07:54:31 +0200 (CEST)
From: Jan Engelhardt <ej@...i.de>
To: Cong Wang <xiyou.wangcong@...il.com>
cc: linux-kernel@...r.kernel.org, pasha.tatashin@...een.com, 
    Cong Wang <cwang@...tikernel.io>, 
    Andrew Morton <akpm@...ux-foundation.org>, Baoquan He <bhe@...hat.com>, 
    Alexander Graf <graf@...zon.com>, Mike Rapoport <rppt@...nel.org>, 
    Changyuan Lyu <changyuanl@...gle.com>, kexec@...ts.infradead.org, 
    linux-mm@...ck.org
Subject: Re: [RFC Patch 0/7] kernel: Introduce multikernel architecture
 support

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).