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

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Message-ID: <1387eeb8-fc61-4894-b12f-6cae3ad920bd@redhat.com>
Date: Thu, 14 Aug 2025 14:59:13 +0200
From: David Hildenbrand <david@...hat.com>
To: Mark Brown <broonie@...nel.org>
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 14.08.25 14:09, Mark Brown wrote:
> 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.

Yeah, the whole prctl() ship has sailed, unfortunately :(

-- 
Cheers

David / dhildenb