linux-kernel - Re: [PATCH 0/3] cgroup/misc: Add hwcap masks to the misc controller

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Message-ID: <6dmgfe5vbbuqw7ycsm4l2ecpv4eppdsau4t22kitjcjglg2gna@dyjlwhfhviif>
Date: Mon, 8 Dec 2025 17:48:47 +0100
From: Michal Koutný <mkoutny@...e.com>
To: Andrei Vagin <avagin@...il.com>
Cc: Chen Ridong <chenridong@...weicloud.com>, 
	Andrei Vagin <avagin@...gle.com>, Kees Cook <kees@...nel.org>, linux-kernel@...r.kernel.org, 
	linux-fsdevel@...r.kernel.org, linux-mm@...ck.org, cgroups@...r.kernel.org, 
	criu@...ts.linux.dev, Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>, 
	Vipin Sharma <vipinsh@...gle.com>, Jonathan Corbet <corbet@....net>
Subject: Re: [PATCH 0/3] cgroup/misc: Add hwcap masks to the misc controller

Hello Andrei.

On Fri, Dec 05, 2025 at 12:19:04PM -0800, Andrei Vagin <avagin@...il.com> wrote:
> If we are talking about C/R use cases, it should be configured when
> container is started. It can be adjusted dynamically, but all changes
> will affect only new processes. The auxiliary vectors are set on execve.

The questions by Ridong are getting at the reasons why cgroup API
doesn't sound like a good match for these values.
I understand it's tempting to implement this by simply copying some
masks from the enclosing cgroup but since there's little to be done upon
(dynamic) change or a process migration it's overkill.

So I'd look at how other [1] adjustments between fork-exec are done and
fit it with them. I guess prctl would be an option as a substitute for
non-existent setauxval().

Thanks,
Michal

[1] Yes, I admit cgroup migration is among them too. Another one is
setns(2) which is IMO a closer concept for this modified view of HW, I'm
not sure whether hardware namespaces had been brought up (and rejected)
in the past.

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