linux-kernel - Re: [RFC 0/5] parker: PARtitioned KERnel

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Message-ID: <40419dea-666e-4a8d-97a7-fa571d7122f4@intel.com>
Date: Wed, 24 Sep 2025 08:22:54 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Fam Zheng <fam.zheng@...edance.com>, linux-kernel@...r.kernel.org
Cc: Lukasz Luba <lukasz.luba@....com>, linyongting@...edance.com,
 songmuchun@...edance.com, satish.kumar@...edance.com,
 Borislav Petkov <bp@...en8.de>, Thomas Gleixner <tglx@...utronix.de>,
 yuanzhu@...edance.com, Ingo Molnar <mingo@...hat.com>,
 Daniel Lezcano <daniel.lezcano@...aro.org>, Zhang Rui <rui.zhang@...el.com>,
 fam@...hon.net, "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
 liangma@...edance.com, Dave Hansen <dave.hansen@...ux.intel.com>,
 "Rafael J. Wysocki" <rafael@...nel.org>, guojinhui.liam@...edance.com,
 linux-pm@...r.kernel.org, Thom Hughes <thom.hughes@...edance.com>
Subject: Re: [RFC 0/5] parker: PARtitioned KERnel

On 9/23/25 08:31, Fam Zheng wrote:
> In terms of fault isolation or security, all kernel instances share
> the same domain, as there is no supervising mechanism. A kernel bug
> in any partition can cause problems for the whole physical machine.
> This is a tradeoff for low-overhead / low-complexity, but hope in
> the future we can take advantage of some hardware mechanism to
> introduce some isolation.
I just don't think this is approach is viable. The buck needs to stop
_somewhere_. You can't just have a bunch of different kernels, with
nothing in charge of the system as a whole.

Just think of bus locks. They affect the whole system. What if one
kernel turns off split lock detection? Or has a different rate limit
than the others? What if one kernel is a big fan of WBINVD? How about
when they use resctrl to partition an L3 cache? How about microcode updates?

I'd just guess that there are a few hundred problems like that. Maybe more.

I'm not saying this won't be useful for a handful of folks in a tightly
controlled environment. But I just don't think it has a place in
mainline where it needs to work for everyone.