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

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Message-ID: <a6479b82-a68c-49f5-8631-b3f536059352@kernel.org>
Date: Mon, 19 Jan 2026 12:11:39 +0100
From: "David Hildenbrand (Red Hat)" <david@...nel.org>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
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 1/19/26 12:06, Lorenzo Stoakes wrote:
> 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 :)
> 

Oh, lol, I ran the wrong test.

Yes, on Fedora config I just get

  $ ./virtual_address_range
TAP version 13
1..1
ok 1 # SKIP prctl(PR_SET_VMA_ANON_NAME) not supported
# 1 skipped test(s) detected. Consider enabling relevant config options 
to improve coverage.
# Totals: pass:0 fail:0 xfail:0 xpass:0 skip:1 error:0

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

Maybe a hardware thing (notebook not supporting 5 level page tables, maybe?)

> 
> 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 (...!)

I cannot really judge, I would have to decipher the details of the tests ...

-- 
Cheers

David