linux-kernel - Re: [PATCH v4 7/7] selftests: prctl: introduce tests for disabling THPs except for madvise

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Message-ID: <47e98636-aace-4a42-b6a4-3c63880f394b@sirena.org.uk>
Date: Thu, 14 Aug 2025 13:09:26 +0100
From: Mark Brown <broonie@...nel.org>
To: David Hildenbrand <david@...hat.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
	Usama Arif <usamaarif642@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org, corbet@....net, rppt@...nel.org,
	surenb@...gle.com, mhocko@...e.com, hannes@...xchg.org,
	baohua@...nel.org, shakeel.butt@...ux.dev, riel@...riel.com,
	ziy@...dia.com, laoar.shao@...il.com, dev.jain@....com,
	baolin.wang@...ux.alibaba.com, npache@...hat.com,
	Liam.Howlett@...cle.com, ryan.roberts@....com, vbabka@...e.cz,
	jannh@...gle.com, Arnd Bergmann <arnd@...db.de>, sj@...nel.org,
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
	kernel-team@...a.com
Subject: Re: [PATCH v4 7/7] selftests: prctl: introduce tests for disabling
 THPs except for madvise

On Thu, Aug 14, 2025 at 02:00:27PM +0200, David Hildenbrand wrote:

> Some people (hello :) ) run tests against distro kernels ... shame that
> prctl just knows one sort of "EINVAL" so we cannot distinguish :(

> But yeah, maybe one has to be more careful of filtering these failures out
> then.

Perhaps this is something that needs considering in the ABI, so
userspace can reasonably figure out if it failed to configure whatever
is being configured due to a missing feature (in which case it should
fall back to not using that feature somehow) or due to it messing
something else up?  We might be happy with the tests being version
specific but general userspace should be able to be a bit more robust.

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