linux-kernel - Re: [PATCH -next v2 2/4] mm: page_table

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Message-ID: <0c95c24d-b980-a8b3-9c68-e10d16e05e10@huawei.com>
Date:   Thu, 24 Mar 2022 10:07:49 +0800
From:   Tong Tiangen <tongtiangen@...wei.com>
To:     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>
Subject: Re: [PATCH -next v2 2/4] mm: page_table_check: add hooks to public
 helpers



在 2022/3/24 1:42, Pasha Tatashin 写道:
> On Tue, Mar 22, 2022 at 10:25 AM Tong Tiangen <tongtiangen@...wei.com> wrote:
>>
>> Move ptep_clear() to the include/linux/pgtable.h and add page table check
>> relate hooks to some helpers, it's prepare for support page table check
>> feature on new architecture.
>>
>> Signed-off-by: Tong Tiangen <tongtiangen@...wei.com>
>> ---
>>   arch/x86/include/asm/pgtable.h | 10 ----------
>>   include/linux/pgtable.h        | 27 +++++++++++++++++++--------
>>   2 files changed, 19 insertions(+), 18 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
>> index 8cd6514e3052..8c85f2eabbaa 100644
>> --- a/arch/x86/include/asm/pgtable.h
>> +++ b/arch/x86/include/asm/pgtable.h
>> @@ -1077,16 +1077,6 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
>>          return pte;
>>   }
>>
>> -#define __HAVE_ARCH_PTEP_CLEAR
>> -static inline void ptep_clear(struct mm_struct *mm, unsigned long addr,
>> -                             pte_t *ptep)
>> -{
>> -       if (IS_ENABLED(CONFIG_PAGE_TABLE_CHECK))
>> -               ptep_get_and_clear(mm, addr, ptep);
>> -       else
>> -               pte_clear(mm, addr, ptep);
>> -}
>> -
>>   #define __HAVE_ARCH_PTEP_SET_WRPROTECT
>>   static inline void ptep_set_wrprotect(struct mm_struct *mm,
>>                                        unsigned long addr, pte_t *ptep)
>> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
>> index f4f4077b97aa..d27fd0ed84a9 100644
>> --- a/include/linux/pgtable.h
>> +++ b/include/linux/pgtable.h
>> @@ -12,6 +12,7 @@
>>   #include <linux/bug.h>
>>   #include <linux/errno.h>
>>   #include <asm-generic/pgtable_uffd.h>
>> +#include <linux/page_table_check.h>
>>
>>   #if 5 - defined(__PAGETABLE_P4D_FOLDED) - defined(__PAGETABLE_PUD_FOLDED) - \
>>          defined(__PAGETABLE_PMD_FOLDED) != CONFIG_PGTABLE_LEVELS
>> @@ -259,14 +260,6 @@ static inline int pmdp_clear_flush_young(struct vm_area_struct *vma,
>>   #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
>>   #endif
>>
>> -#ifndef __HAVE_ARCH_PTEP_CLEAR
>> -static inline void ptep_clear(struct mm_struct *mm, unsigned long addr,
>> -                             pte_t *ptep)
>> -{
>> -       pte_clear(mm, addr, ptep);
>> -}
>> -#endif
>> -
>>   #ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR
>>   static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
>>                                         unsigned long address,
>> @@ -274,10 +267,23 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
>>   {
>>          pte_t pte = *ptep;
>>          pte_clear(mm, address, ptep);
>> +       page_table_check_pte_clear(mm, address, pte);
>>          return pte;
>>   }
>>   #endif
>>
>> +#ifndef __HAVE_ARCH_PTEP_CLEAR
>> +static inline void ptep_clear(struct mm_struct *mm, unsigned long addr,
>> +                             pte_t *ptep)
>> +{
>> +#ifdef CONFIG_PAGE_TABLE_CHECK
>> +       ptep_get_and_clear(mm, addr, ptep);
>> +#else
>> +       pte_clear(mm, addr, ptep);
>> +#endif
> 
> I have a preference to use if (IS_ENABLED(CONFIG_PAGE_TABLE_CHECK))
> instead of #ifdef. The end result is the same. Otherwise it looks
> good.
> 
> Thanks,
> Pasha
> .

I have a little hesitation when making this change , in theory, add if 
here may affect the performance a little in some scenarios. However, the 
impact on the whole call path should be small.

I will send v3 using if (IS_ENABLED(CONFIG_PAGE_TABLE_CHECK)).

Thanks.
Tong
.