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

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Date:   Wed, 23 Mar 2022 13:42:16 -0400
From:   Pasha Tatashin <pasha.tatashin@...een.com>
To:     Tong Tiangen <tongtiangen@...wei.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

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