linux-kernel - Re: [PATCH V2] mm/debug_vm_pgtable: Add [pte|pmd]_mkwrite

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Message-ID: <b5a1b52c-75ef-4915-a254-a502b9f78eeb@arm.com>
Date: Wed, 22 Oct 2025 13:28:43 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: "Huang, Ying" <ying.huang@...ux.alibaba.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
 David Hildenbrand <david@...hat.com>, linux-kernel@...r.kernel.org,
 Catalin Marinas <catalin.marinas@....com>
Subject: Re: [PATCH V2] mm/debug_vm_pgtable: Add [pte|pmd]_mkwrite_novma()
 tests

On 22/10/25 1:03 PM, Huang, Ying wrote:
> Anshuman Khandual <anshuman.khandual@....com> writes:
> 
>> Add some [pte|pmd]_mkwrite_novma() relevant tests.
>>
>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>> Cc: David Hildenbrand <david@...hat.com>
>> Cc: Huang Ying <ying.huang@...ux.alibaba.com>
>> Cc: linux-mm@...ck.org
>> Cc: linux-kernel@...r.kernel.org
>> Suggested-by: Catalin Marinas <catalin.marinas@....com>
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
>> ---
>> These tests clear on arm64 platform after the following recent patch.
>>
>> https://lore.kernel.org/all/20251015023712.46598-1-ying.huang@linux.alibaba.com/
>>
>> Changes in V2:
>>
>> - Added a new test combination per Huang
>>
>> Changes in V1:
>>
>> https://lore.kernel.org/all/20251021024424.2390325-1-anshuman.khandual@arm.com/
>>
>>  mm/debug_vm_pgtable.c | 12 ++++++++++++
>>  1 file changed, 12 insertions(+)
>>
>> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
>> index 830107b6dd08..def344bb4a32 100644
>> --- a/mm/debug_vm_pgtable.c
>> +++ b/mm/debug_vm_pgtable.c
>> @@ -102,6 +102,12 @@ static void __init pte_basic_tests(struct pgtable_debug_args *args, int idx)
>>  	WARN_ON(pte_write(pte_wrprotect(pte_mkwrite(pte, args->vma))));
>>  	WARN_ON(pte_dirty(pte_wrprotect(pte_mkclean(pte))));
>>  	WARN_ON(!pte_dirty(pte_wrprotect(pte_mkdirty(pte))));
>> +
>> +	WARN_ON(!pte_dirty(pte_mkwrite_novma(pte_mkdirty(pte))));
>> +	WARN_ON(pte_dirty(pte_mkwrite_novma(pte_mkclean(pte))));
>> +	WARN_ON(!pte_write(pte_mkdirty(pte_mkwrite_novma(pte))));
> 
> Why do you use
> 
> pte_mkwrite_novma(pte)
> 
> instead of
> 
> pte_mkwrite(pte, args->vma)
Just wanted to have more coverage for pte_mkwrite_novma() helper which was missing
till now in this test. But just wondering is there a specific reason for replacing
this with pte_mkwrite() helper instead here ? Also we could probably add tests for
both these helper variations if that is preferred.