Messages in this thread | | | Date | Thu, 24 Mar 2022 10:44:25 +0800 | Subject | Re: [PATCH -next v2 2/4] mm: page_table_check: add hooks to public helpers | From | Tong Tiangen <> |
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在 2022/3/24 10:12, Pasha Tatashin 写道: > On Wed, Mar 23, 2022 at 10:07 PM Tong Tiangen <tongtiangen@huawei.com> wrote: >> >> >> >> 在 2022/3/24 1:42, Pasha Tatashin 写道: >>> On Tue, Mar 22, 2022 at 10:25 AM Tong Tiangen <tongtiangen@huawei.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@huawei.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 do not think so, the compiler should optimize out IS_ENABLED() when > not enabled, no? >
You are right.
https://www.kernel.org/doc/Documentation/process/coding-style.rst
The compiler will constant-fold the conditional away, and include or exclude the block of code just as with an #ifdef, so this will **not add any runtime overhead**.
Thanks :)
>> >> I will send v3 using if (IS_ENABLED(CONFIG_PAGE_TABLE_CHECK)). >> >> Thanks. >> Tong >> . > .
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