From 8f79a13045f06bbbee0eb2f6c4246ad13b1191b8 Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Fri, 14 Jun 2019 10:55:05 +0200 Subject: [PATCH] x86/mm: provide pmdp_establish() helper BugLink: https://bugs.launchpad.net/bugs/1830433 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 lose 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. [akpm@linux-foundation.org: add missing `do' to do-while loop] Link: http://lkml.kernel.org/r/20171213105756.69879-10-kirill.shutemov@linux.intel.com Signed-off-by: Kirill A. Shutemov Cc: Ingo Molnar Cc: H. Peter Anvin Cc: Thomas Gleixner Cc: Vlastimil Babka Cc: Andrea Arcangeli Cc: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds (cherry picked from commit 86fa949b050184ffc53688516a6a83ae5f98d08a) Tested-by: Connor Kuehl Signed-off-by: Andrea Righi Acked-by: Stefan Bader Acked-by: Thadeu Lima de Souza Cascardo Signed-off-by: Khalid Elmously --- 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 a18fa4eac97b..a564084c6141 100644 --- a/arch/x86/include/asm/pgtable-3level.h +++ b/arch/x86/include/asm/pgtable-3level.h @@ -161,7 +161,6 @@ 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; @@ -169,6 +168,8 @@ 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; @@ -184,6 +185,40 @@ 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; + } + + do { + 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 f3f8409f549c..c9f9d2334866 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -1177,6 +1177,21 @@ static inline int pud_write(pud_t pud) return pud_flags(pud) & _PAGE_RW; } +#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 + /* * Page table pages are page-aligned. The lower half of the top * level is used for userspace and the top half for the kernel. -- 2.39.2