We need an atomic way to setup pmd page table entry, avoiding races with CPU setting dirty/accessed bits. This is required to implement pmdp_invalidate() that doesn't loose these bits.
On PAE we can avoid expensive cmpxchg8b for cases when new page table entry is not present. If it's present, fallback to cpmxchg loop. Signed-off-by: Kirill A. Shutemov <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Thomas Gleixner <[email protected]> --- arch/x86/include/asm/pgtable-3level.h | 37 ++++++++++++++++++++++++++++++++++- arch/x86/include/asm/pgtable.h | 15 ++++++++++++++ 2 files changed, 51 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/pgtable-3level.h b/arch/x86/include/asm/pgtable-3level.h index c8821bab938f..cd73be22be1d 100644 --- a/arch/x86/include/asm/pgtable-3level.h +++ b/arch/x86/include/asm/pgtable-3level.h @@ -157,7 +157,6 @@ static inline pte_t native_ptep_get_and_clear(pte_t *ptep) #define native_ptep_get_and_clear(xp) native_local_ptep_get_and_clear(xp) #endif -#ifdef CONFIG_SMP union split_pmd { struct { u32 pmd_low; @@ -165,6 +164,8 @@ union split_pmd { }; pmd_t pmd; }; + +#ifdef CONFIG_SMP static inline pmd_t native_pmdp_get_and_clear(pmd_t *pmdp) { union split_pmd res, *orig = (union split_pmd *)pmdp; @@ -180,6 +181,40 @@ static inline pmd_t native_pmdp_get_and_clear(pmd_t *pmdp) #define native_pmdp_get_and_clear(xp) native_local_pmdp_get_and_clear(xp) #endif +#ifndef pmdp_establish +#define pmdp_establish pmdp_establish +static inline pmd_t pmdp_establish(struct vm_area_struct *vma, + unsigned long address, pmd_t *pmdp, pmd_t pmd) +{ + pmd_t old; + + /* + * If pmd has present bit cleared we can get away without expensive + * cmpxchg64: we can update pmdp half-by-half without racing with + * anybody. + */ + if (!(pmd_val(pmd) & _PAGE_PRESENT)) { + union split_pmd old, new, *ptr; + + ptr = (union split_pmd *)pmdp; + + new.pmd = pmd; + + /* xchg acts as a barrier before setting of the high bits */ + old.pmd_low = xchg(&ptr->pmd_low, new.pmd_low); + old.pmd_high = ptr->pmd_high; + ptr->pmd_high = new.pmd_high; + return old.pmd; + } + + { + old = *pmdp; + } while (cmpxchg64(&pmdp->pmd, old.pmd, pmd.pmd) != old.pmd); + + return old; +} +#endif + #ifdef CONFIG_SMP union split_pud { struct { diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index 5b4c44d419c5..ff19dbd6c93d 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -1111,6 +1111,21 @@ static inline void pmdp_set_wrprotect(struct mm_struct *mm, clear_bit(_PAGE_BIT_RW, (unsigned long *)pmdp); } +#ifndef pmdp_establish +#define pmdp_establish pmdp_establish +static inline pmd_t pmdp_establish(struct vm_area_struct *vma, + unsigned long address, pmd_t *pmdp, pmd_t pmd) +{ + if (IS_ENABLED(CONFIG_SMP)) { + return xchg(pmdp, pmd); + } else { + pmd_t old = *pmdp; + *pmdp = pmd; + return old; + } +} +#endif + /* * clone_pgd_range(pgd_t *dst, pgd_t *src, int count); * -- 2.14.1
