linux-kernel - Re: [PATCH V3] selftests: vm: Add test for Soft-Dirty PTE bit

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Date:   Thu, 03 Mar 2022 13:39:20 -0500
From:   Gabriel Krisman Bertazi <krisman@...labora.com>
To:     Shuah Khan <skhan@...uxfoundation.org>
Cc:     David Hildenbrand <david@...hat.com>,
        Muhammad Usama Anjum <usama.anjum@...labora.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shuah Khan <shuah@...nel.org>, kernel@...labora.com,
        kernelci@...ups.io, Will Deacon <will@...nel.org>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH V3] selftests: vm: Add test for Soft-Dirty PTE bit

Shuah Khan <skhan@...uxfoundation.org> writes:

> On 2/28/22 2:37 AM, David Hildenbrand wrote:
>> On 24.02.22 22:23, Muhammad Usama Anjum wrote:
>>> This introduces three tests:
>>> 1) Sanity check soft dirty basic semantics: allocate area, clean, dirty,
>>> check if the SD bit flipped.
>>> 2) Check VMA reuse: validate the VM_SOFTDIRTY usage
>>> 3) Check soft-dirty on huge pages
>>>
>>> This was motivated by Will Deacon's fix commit 912efa17e512 ("mm: proc:
>>> Invalidate TLB after clearing soft-dirty page state"). I was tracking the
>>> same issue that he fixed, and this test would have caught it.
>>>
>> A note that madv_populate.c already contains some SOFTDIRTY tests
>> regarding MADV_POPULATE. Eventually we want to factor out
>> softdirty/pagemap handling+checks for easier reuse.
>> 
>
> Is this patch unnecessary then?

It is not unnecessary since the madv test doesn't cover the bug tested
here, afaik.  But, as mentioned when I originally submitted this patch,
it should be merged into selftests/vm/madv_populate.c or, at least,
reuse that existing infrastructure.

https://lore.kernel.org/lkml/87lf553z5g.fsf@collabora.com/

-- 
Gabriel Krisman Bertazi