Message-Id: <BC25CE95-75A1-48E7-86E7-4E5E933761B8@flygoat.com>
Date: Thu, 25 Sep 2025 23:47:43 +0800
From: Jiaxun Yang <jiaxun.yang@...goat.com>
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



> 2025年9月19日 06:25，Cong Wang <xiyou.wangcong@...il.com> 写道：
> 
> 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.

Hi Cong,

Sorry for chime in here, and thanks for brining replicated-kernel back to the life.

I have some experience on original Popcorn Linux [1] [2], which seems to be the
root of most code in this series, please see my comments below.

> 
> The multikernel architecture provides several key benefits:
> - Improved fault isolation between different workloads
> - Enhanced security through kernel-level separation

I’d agree with Stefen’s comments [3], an "isolation” solution is critical for adaptation
of multikernel OS, given that multi-tenant system is almost everywhere.

Also allowing other kernel to inject IPI without any restriction can impose DOS attack
risk.

> - Better resource utilization than traditional VM (KVM, Xen etc.)
> - Potential zero-down kernel update with KHO (Kernel Hand Over)
> 
> Architecture Overview:
> The implementation leverages kexec infrastructure to load and manage
> multiple kernel images, with each kernel instance assigned to specific
> CPU cores. Inter-kernel communication is facilitated through a dedicated
> IPI framework that allows kernels to coordinate and share information
> when necessary.
> 
> Key Components:
> 1. Enhanced kexec subsystem with dynamic kimage tracking
> 2. Generic IPI communication framework for inter-kernel messaging

I actually have concerns over inter-kernel communication. The origin Popcorn
IPI protocol, which seems to be inherited here, was designed as a prototype,
without much consideration on the ecosystem. It would be nice if we can reused
existing infra design for inter kernel communication.

I would suggest look into OpenAMP [4] and remoteproc subsystem in kernel. They
already have mature solutions on communication between different kernels over coherent
memory and mailboxes (rpmsg [5] co). They also defined ELF extensions to pass side band
information for other kernel images. 

Linaro folks are also working on a new VirtIO transport called virtio-msg [6], [7], which is designed
with Linux-Linux hardware partitioning scenario in mind.

> 3. Architecture-specific CPU bootstrap mechanisms (only x86 so far)
> 4. Proc interface for monitoring loaded kernel instances
> 
> 

[…]

Thanks
- Jiaxun

[1]: https://www.kernel.org/doc/ols/2014/ols2014-barbalace.pdf
[2]: https://sourceforge.net/projects/popcornlinux/
[3]: https://lore.kernel.org/all/CAM_iQpXnHr7WC6VN3WB-+=CZGF5pyfo9y9D4MCc_Wwgp29hBrw@mail.gmail.com/
[4]: https://www.openampproject.org/
[5]: https://docs.kernel.org/staging/rpmsg.html
[6]: https://linaro.atlassian.net/wiki/spaces/HVAC/overview
[7]: https://lwn.net/Articles/1031928/

> 
> 
> --
> 2.34.1

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