linux-kernel - Re: [Patch v2] x86/head/64: remove redundant check on level2_kernel_pgt's _PAGE

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Message-ID: <20240523122604.2owqxj7fmgudewzk@master>
Date: Thu, 23 May 2024 12:26:04 +0000
From: Wei Yang <richard.weiyang@...il.com>
To: "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Cc: Wei Yang <richard.weiyang@...il.com>, tglx@...utronix.de,
	mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
	x86@...nel.org, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...nel.org>, Steve Wahl <steve.wahl@....com>
Subject: Re: [Patch v2] x86/head/64: remove redundant check on
 level2_kernel_pgt's _PAGE_PRESENT bit

Thanks for comment.

On Thu, May 23, 2024 at 01:33:28PM +0300, Kirill A . Shutemov wrote:
>On Thu, May 23, 2024 at 08:37:52AM +0000, Wei Yang wrote:
>> This patch tries to remove a redundant check on kernel code's PMD
>> _PAGE_PRESENT attribute before fix up.
>
>Tries? s/This patch tries to r/R/

Will use this one.

>
>> Current process looks like this:
>> 
>>     pmd in [0, _text)
>>         unset _PAGE_PRESENT
>>     pmd in [_text, _end]
>>         if (_PAGE_PRESENT)
>>             fix up delta
>>     pmd in (_end, 512)
>>         unset _PAGE_PRESENT
>> 
>> Since we have compiled in _PAGE_PRESENT in this page table, it is not
>> necessary to check _PAGE_PRESENT again before fixing up delta
>
>level2_kernel_pgt compiled with _PAGE_PRESENT set. The check is
>redundant.
>

Will use this one, thanks

>
>-- 
>  Kiryl Shutsemau / Kirill A. Shutemov

-- 
Wei Yang
Help you, Help me