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

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Message-ID: <87o6pzbbks.fsf@DESKTOP-5N7EMDA>
Date: Wed, 22 Oct 2025 16:11:15 +0800
From: "Huang, Ying" <ying.huang@...ux.alibaba.com>
To: Anshuman Khandual <anshuman.khandual@....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

Anshuman Khandual <anshuman.khandual@....com> writes:

> 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.

IIUC, pte_mkwrite() is a more formal interface.  pte_mkwrite_novma() is
used to implement pte_mkwrite().  So, IMHO, we should use the more
formal pte_mkwrite() interface if possible.

---
Best Regards,
Huang, Ying