linux-kernel - Re: [PATCH v3 2/4] selftests/mm: virtual_address

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Message-ID: <059fcb77-7eea-4e3d-9b70-d88975388d9b@redhat.com>
Date: Tue, 14 Jan 2025 14:11:58 +0100
From: David Hildenbrand <david@...hat.com>
To: Thomas Weißschuh <thomas.weissschuh@...utronix.de>,
 Andrew Morton <akpm@...ux-foundation.org>, Shuah Khan <shuah@...nel.org>,
 Dev Jain <dev.jain@....com>, Thomas Gleixner <tglx@...utronix.de>
Cc: linux-mm@...ck.org, linux-kselftest@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/4] selftests/mm: virtual_address_range: Unmap chunks
 after validation

On 13.01.25 14:15, Thomas Weißschuh wrote:
> For each accessed chunk a PTE is created.
> More than 1GiB of PTEs is used in this way.
> Remove each PTE after validating a chunk to reduce peak memory usage.
> 
> It is important to only unmap memory that previously mmap()ed,
> as unmapping other mappings like the stack, heap or executable mappings
> will crash the process.
> The mappings read from /proc/self/maps and the return values from mmap()
> don't allow a simple correlation due to merging and no guaranteed order.
> To correlate the pointers and mappings use prctl(PR_SET_VMA_ANON_NAME).
> While it introduces a test dependency, other alternatives would
> introduce runtime or development overhead.
> 
> Fixes: 010409649885 ("selftests/mm: confirm VA exhaustion without reliance on correctness of mmap()")
> Signed-off-by: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
> ---

Acked-by: David Hildenbrand <david@...hat.com>

-- 
Cheers,

David / dhildenb