linux-kernel - Re: [PATCH -next v4 1/4] mm: page_table_check: move pxx_user_accessible

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Date:   Thu, 21 Apr 2022 09:14:54 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Tong Tiangen <tongtiangen@...wei.com>,
        Pasha Tatashin <pasha.tatashin@...een.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-mm <linux-mm@...ck.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        linux-riscv@...ts.infradead.org,
        Kefeng Wang <wangkefeng.wang@...wei.com>,
        Guohanjun <guohanjun@...wei.com>
Subject: Re: [PATCH -next v4 1/4] mm: page_table_check: move
 pxx_user_accessible_page into x86



On 4/21/22 08:35, Tong Tiangen wrote:
> 
> 
> 在 2022/4/21 0:44, Pasha Tatashin 写道:
>> On Wed, Apr 20, 2022 at 2:45 AM Tong Tiangen <tongtiangen@...wei.com> wrote:
>>>
>>>
>>>
>>> 在 2022/4/19 17:29, Anshuman Khandual 写道:
>>>>
>>>>
>>>> On 4/18/22 09:14, Tong Tiangen wrote:
>>>>> --- a/mm/page_table_check.c
>>>>> +++ b/mm/page_table_check.c
>>>>> @@ -10,6 +10,14 @@
>>>>>    #undef pr_fmt
>>>>>    #define pr_fmt(fmt)        "page_table_check: " fmt
>>>>>
>>>>> +#ifndef PMD_PAGE_SIZE
>>>>> +#define PMD_PAGE_SIZE       PMD_SIZE
>>>>> +#endif
>>>>> +
>>>>> +#ifndef PUD_PAGE_SIZE
>>>>> +#define PUD_PAGE_SIZE       PUD_SIZE
>>>>> +#endif
>>>>
>>>> Why cannot PMD_SIZE/PUD_SIZE be used on every platform instead ? What is the
>>>> need for using PUD_PAGE_SIZE/PMD_PAGE_SIZE ? Are they different on x86 ?
>>>> .
>>>
>>> Hi, Pasha：
>>> I checked the definitions of PMD_SIZE/PUD_SIZE and
>>> PUD_PAGE_SIZE/PMD_PAGE_SIZE in x86 architecture and their use outside
>>> the architecture(eg: in mm/, all used PMD_SIZE/PUD_SIZE), Would it be
>>> better to use a unified PMD_SIZE/PUD_SIZE here?
>>
>> Hi Tong,
>>
>> Yes, it makes sense to use PMD_SIZE/PUD_SIZE instead of
>> PUD_PAGE_SIZE/PMD_PAGE_SIZE in page_table_check to be inline with the
>> rest of the mm/
>>
>> Pasha
>>
> Hi Pasha and Anshuman:
> 
> OK, Functional correctness is not affected here, i plan to optimize this point after this patchset is merged.

As page table check is now being proposed to be supported on multiple platforms i.e
arm64, riscv besides just x86, it should not have any architecture specific macros
or functions. Hence please do generalize these PMD/PUD sizes in this series itself.