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Date:   Mon, 11 Dec 2023 10:46:23 -0800
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Subject: Re: [PATCH v6 5/5] selftests/mm: add UFFDIO_MOVE ioctl test
To:     David Hildenbrand <david@redhat.com>,
        Suren Baghdasaryan <surenb@google.com>,
        Mark Brown <broonie@kernel.org>
Cc:     akpm@linux-foundation.org, viro@zeniv.linux.org.uk,
        brauner@kernel.org, shuah@kernel.org, aarcange@redhat.com,
        lokeshgidra@google.com, peterx@redhat.com, ryan.roberts@arm.com,
        hughd@google.com, mhocko@suse.com, axelrasmussen@google.com,
        rppt@kernel.org, willy@infradead.org, Liam.Howlett@oracle.com,
        jannh@google.com, zhangpeng362@huawei.com, bgeffon@google.com,
        kaleshsingh@google.com, ngeoffray@google.com, jdduke@google.com,
        linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org,
        kernel-team@android.com, Peter Zijlstra <peterz@infradead.org>
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From:   John Hubbard <jhubbard@nvidia.com>
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On 12/11/23 08:32, David Hildenbrand wrote:
...
> That's an open question: do we want to be able to build selftests 
> against any host headers, and not the in-tree headers that have to be 
> manually installed and dirty the git tree?
> 
> One obvious drawbacks is that we'll have to deal with all that using a 
> bunch of #ifdef, and the tests that will be built+run will depend on the 
> host headers.
> 
> Especially the letter is relevant I think: Our upstream testing won't be 
> able to build+run tests that rely on new upstream features. But that's 
> what some key benefit of these selftests, and being able to run them 
> automatically on a bunch of different combinations upstream.
> 
> Further, the tests are closely related to the given kernel version, they 
> are not some completely separate tests.
> 
> 
> Moving the the (MM?) selftests to a separate repository would make the 
> decision easier: just like in QEMU etc, we'd simply pull in a headers 
> update and only build against these archived headers.
> 
> So I see the options:
> 
> (1) Rely on installing the proper in-tree headers. Build will fail if
>      that is not happening.
> 
> (2) Make the tests build with any host headers.
> 
> (3) Regularly archive the required headers in the selftest directory
>      like external projects like QEMU do.

Or (4) Hack in little ifdef snippets, into the selftests, like we used
to do. Peter Zijlstra seems to be asking for this, if I understand his
(much) earlier comments about this.


thanks,
-- 
John Hubbard
NVIDIA