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

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Date:   Thu, 3 Mar 2022 14:46:08 -0700
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Gabriel Krisman Bertazi <krisman@...labora.com>
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,
        Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH V3] selftests: vm: Add test for Soft-Dirty PTE bit

On 3/3/22 11:39 AM, Gabriel Krisman Bertazi wrote:
> 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/
> 

Oops this one came in a few months ago and appears to have slipped
through and didn't get the right attention. Sorry about that.

Please resend the patch and cc all the everybody on this thread.

I would like to have your patch reviewed and looked at first. This
patch needs rework sine it has several comments to be addressed.

thanks,
-- Shuah