linux-kernel - Re: [PATCH] selftests/mm: remove virtual_address

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Message-ID: <53c0f278-6029-45f3-b3db-e2b70f323abe@lucifer.local>
Date: Mon, 19 Jan 2026 11:11:18 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Dev Jain <dev.jain@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...nel.org>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
        Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-kselftest@...r.kernel.org, Mark Brown <broonie@...nel.org>,
        aneesh.kumar@...nel.org, Anshuman Khandual <anshuman.khandual@....com>
Subject: Re: [PATCH] selftests/mm: remove virtual_address_range test

On Mon, Jan 19, 2026 at 08:59:01AM +0000, Lorenzo Stoakes wrote:
> Anyway.
>
> Practically speaking I think there are two ways forward here (not mutually
> exclusive):
>
> 1. Implement something in kunit or similar that explicitly tests
>    get_unmapped_area().
>
> 2. Add a _new_ selftest, named something sensible like mmap_hint.c or something,
>    that runs only on relevant arches, and does NOT try to do crazy stuff like
>    mapping the entire VA space, but instead simply tries some trial unhinted
>    mappings some hints in 48-bit space, and some hints in 52-bit space and
>    asserts things are as expected.
>
> If you do point 2, please please use a. use the kselftest_harness.h to write the
> tests in a nice way (see e.g. guard-regions.c for an example of how it's used)
> and b. use the procmap helpers in vm_util.h to check on VMA ranges, you can see
> how they're used in... the merge.c tests you so deride :)
>
> If you or others do both/either I promise to dedicate review resource to the
> series(es). That fair enough?
>
> Thanks, Lorenzo

It seems to me that the va_high_addr_switch test is already asserting all
we need unless I'm missing something, so unless I'm much mistaken I think
simply removing this test is the right way forward.

A kunit test for get_unmapped_area() (if possible, as not exported) would
still be useful, however.

Cheers, Lorenzo