Re: [PATCH -next v2 2/4] mm: page_table_check: add hooks to public helpers

[Tong Tiangen <tongtiangen@xxxxxxxxxx>]

在 2022/3/24 1:42, Pasha Tatashin 写道:
> On Tue, Mar 22, 2022 at 10:25 AM Tong Tiangen <tongtiangen@xxxxxxxxxx> 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@xxxxxxxxxx>
> > ---
> >   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
.