linux-kernel - Re: [PATCH] x86/mm: Make pud_present() check _PAGE_PROTNONE and _PAGE

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Message-ID: <0a3ac234-303c-26b7-abb7-de42025b3e0d@arm.com>
Date:   Sun, 22 Mar 2020 06:30:35 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     John Hubbard <jhubbard@...dia.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>
Cc:     linux-mm@...ck.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org,
        Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH] x86/mm: Make pud_present() check _PAGE_PROTNONE and
 _PAGE_PSE as well



On 03/21/2020 01:20 AM, John Hubbard wrote:
> On 3/20/20 6:22 AM, Anshuman Khandual wrote:
> ...
>>>> +Cc: Kirill A. Shutemov <kirill@...temov.name>
>>>> +Cc: Dan Williams <dan.j.williams@...el.com>
>>>
>>> Or we can just drop the pud_mknotpresent(). There's no users AFAICS and
>>> only x86 provides it.
> 
> +1
> 
>>
>> Yes that will be an option but IMHO fixing pud_present() here might be
>> a better choice because,
>>
>> (1) pud_mknotpresent() with fixed pud_present() might be required later
> 
> 
> It might. Or it might not. Let's wait until it's actually used, and see.
> Dead code is an avoidable expense (adds size, space on the screen, email
> traffic and other wasted time), so let's avoid it here.


Sure, will resend with pud_mknotpresent() dropped.

> 
> 
>> (2) PMD & PUD will be exact same (THP is supported on either level)
>>
>> Nonetheless, I am happy to go either way.
>>
> 
> 
> thanks,