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

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Message-ID: <79d2636a-bb15-4c7f-a633-c4bf408a2bc8@lucifer.local>
Date: Mon, 19 Jan 2026 11:06:29 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: "David Hildenbrand (Red Hat)" <david@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.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>
Subject: Re: [PATCH] selftests/mm: remove virtual_address_range test

On Mon, Jan 19, 2026 at 11:39:51AM +0100, David Hildenbrand (Red Hat) wrote:
> On
>
> $ uname -r
> 6.18.4-200.fc43.x86_64
>
> I am getting
>
> $ ./va_high_addr_switch
> mmap(addr_switch_hint - pagesize, pagesize): 0x7fe7de6d7000 - OK
> mmap(addr_switch_hint - pagesize, (2 * pagesize)): 0x7fe7de6d6000 - OK
> mmap(addr_switch_hint, pagesize): 0x7fe7de6d7000 - OK
> mmap(addr_switch_hint, 2 * pagesize, MAP_FIXED): 0xffffffffffffffff - FAILED
> mmap(NULL): 0x7fe7de6d5000 - OK
> mmap(low_addr): 0x40000000 - OK
> mmap(high_addr): 0x7fe7de6d5000 - OK
> mmap(high_addr) again: 0x7fe7de6d3000 - OK
> mmap(high_addr, MAP_FIXED): 0xffffffffffffffff - FAILED
> mmap(-1): 0x7fe7de6d1000 - OK
> mmap(-1) again: 0x7fe7de6cf000 - OK
> mmap(addr_switch_hint - pagesize, pagesize): 0x7fe7de6d0000 - OK
> mmap(addr_switch_hint - pagesize, 2 * pagesize): 0x7fe7de6cf000 - OK
> mmap(addr_switch_hint - pagesize/2 , 2 * pagesize): 0x7fe7de6cd000 - OK
> mmap(addr_switch_hint, pagesize): 0x7fe7de6cc000 - OK
> mmap(addr_switch_hint, 2 * pagesize, MAP_FIXED): 0xffffffffffffffff - FAILED
>
>
> Are these the same issues you see?

No, that's entirely separate bug it seems :)

Seems to work locally for me on 6.18.3, and also in VM with tip mm-unstable,
strange.

The issue here is with virtual_address_space.c which seems to just to be
generally broken, I couldn't even bisect to a working one, and I really did
try.

Actually hang on, isn't va_high_addr_space already then testing what
virtual_address_space should be testing anyway if it were sensible??

That suggests then that just removing virtual_address_space without
replacement (since this already exists) is the right way (...!)

Thanks, Lorenzo