From 394290cba9664ed3ab80d0e247402102a9b7287a Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Fri, 26 Jul 2024 17:07:26 +0200 Subject: [PATCH] mm: turn USE_SPLIT_PTE_PTLOCKS / USE_SPLIT_PTE_PTLOCKS into Kconfig options Patch series "mm: split PTE/PMD PT table Kconfig cleanups+clarifications". This series is a follow up to the fixes: "[PATCH v1 0/2] mm/hugetlb: fix hugetlb vs. core-mm PT locking" When working on the fixes, I wondered why 8xx is fine (-> never uses split PT locks) and how PT locking even works properly with PMD page table sharing (-> always requires split PMD PT locks). Let's improve the split PT lock detection, make hugetlb properly depend on it and make 8xx bail out if it would ever get enabled by accident. As an alternative to patch #3 we could extend the Kconfig SPLIT_PTE_PTLOCKS option from patch #2 -- but enforcing it closer to the code that actually implements it feels a bit nicer for documentation purposes, and there is no need to actually disable it because it should always be disabled (!SMP). Did a bunch of cross-compilations to make sure that split PTE/PMD PT locks are still getting used where we would expect them. [1] https://lkml.kernel.org/r/20240725183955.2268884-1-david@redhat.com This patch (of 3): Let's clean that up a bit and prepare for depending on CONFIG_SPLIT_PMD_PTLOCKS in other Kconfig options. More cleanups would be reasonable (like the arch-specific "depends on" for CONFIG_SPLIT_PTE_PTLOCKS), but we'll leave that for another day. Link: https://lkml.kernel.org/r/20240726150728.3159964-1-david@redhat.com Link: https://lkml.kernel.org/r/20240726150728.3159964-2-david@redhat.com Signed-off-by: David Hildenbrand Acked-by: Mike Rapoport (Microsoft) Reviewed-by: Russell King (Oracle) Reviewed-by: Qi Zheng Cc: Alexander Viro Cc: Borislav Petkov Cc: Boris Ostrovsky Cc: Christian Brauner Cc: Christophe Leroy Cc: Dave Hansen Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: Juergen Gross Cc: Michael Ellerman Cc: Muchun Song Cc: "Naveen N. Rao" Cc: Nicholas Piggin Cc: Oscar Salvador Cc: Peter Xu Cc: Thomas Gleixner Signed-off-by: Andrew Morton --- arch/arm/mm/fault-armv.c | 6 +++--- arch/x86/xen/mmu_pv.c | 7 ++++--- include/linux/mm.h | 8 ++++---- include/linux/mm_types.h | 2 +- include/linux/mm_types_task.h | 3 --- kernel/fork.c | 4 ++-- mm/Kconfig | 18 +++++++++++------- mm/memory.c | 2 +- 8 files changed, 26 insertions(+), 24 deletions(-) diff --git a/arch/arm/mm/fault-armv.c b/arch/arm/mm/fault-armv.c index 2286c2ea60ec..831793cd6ff9 100644 --- a/arch/arm/mm/fault-armv.c +++ b/arch/arm/mm/fault-armv.c @@ -61,7 +61,7 @@ static int do_adjust_pte(struct vm_area_struct *vma, unsigned long address, return ret; } -#if USE_SPLIT_PTE_PTLOCKS +#if defined(CONFIG_SPLIT_PTE_PTLOCKS) /* * If we are using split PTE locks, then we need to take the page * lock here. Otherwise we are using shared mm->page_table_lock @@ -80,10 +80,10 @@ static inline void do_pte_unlock(spinlock_t *ptl) { spin_unlock(ptl); } -#else /* !USE_SPLIT_PTE_PTLOCKS */ +#else /* !defined(CONFIG_SPLIT_PTE_PTLOCKS) */ static inline void do_pte_lock(spinlock_t *ptl) {} static inline void do_pte_unlock(spinlock_t *ptl) {} -#endif /* USE_SPLIT_PTE_PTLOCKS */ +#endif /* defined(CONFIG_SPLIT_PTE_PTLOCKS) */ static int adjust_pte(struct vm_area_struct *vma, unsigned long address, unsigned long pfn) diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c index f1ce39d6d32c..f4a316894bbb 100644 --- a/arch/x86/xen/mmu_pv.c +++ b/arch/x86/xen/mmu_pv.c @@ -665,7 +665,7 @@ static spinlock_t *xen_pte_lock(struct page *page, struct mm_struct *mm) { spinlock_t *ptl = NULL; -#if USE_SPLIT_PTE_PTLOCKS +#if defined(CONFIG_SPLIT_PTE_PTLOCKS) ptl = ptlock_ptr(page_ptdesc(page)); spin_lock_nest_lock(ptl, &mm->page_table_lock); #endif @@ -1553,7 +1553,8 @@ static inline void xen_alloc_ptpage(struct mm_struct *mm, unsigned long pfn, __set_pfn_prot(pfn, PAGE_KERNEL_RO); - if (level == PT_PTE && USE_SPLIT_PTE_PTLOCKS && !pinned) + if (level == PT_PTE && IS_ENABLED(CONFIG_SPLIT_PTE_PTLOCKS) && + !pinned) __pin_pagetable_pfn(MMUEXT_PIN_L1_TABLE, pfn); xen_mc_issue(XEN_LAZY_MMU); @@ -1581,7 +1582,7 @@ static inline void xen_release_ptpage(unsigned long pfn, unsigned level) if (pinned) { xen_mc_batch(); - if (level == PT_PTE && USE_SPLIT_PTE_PTLOCKS) + if (level == PT_PTE && IS_ENABLED(CONFIG_SPLIT_PTE_PTLOCKS)) __pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, pfn); __set_pfn_prot(pfn, PAGE_KERNEL); diff --git a/include/linux/mm.h b/include/linux/mm.h index 6c2078ca3391..b7000fa300f3 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2891,7 +2891,7 @@ static inline void pagetable_free(struct ptdesc *pt) __free_pages(page, compound_order(page)); } -#if USE_SPLIT_PTE_PTLOCKS +#if defined(CONFIG_SPLIT_PTE_PTLOCKS) #if ALLOC_SPLIT_PTLOCKS void __init ptlock_cache_init(void); bool ptlock_alloc(struct ptdesc *ptdesc); @@ -2949,7 +2949,7 @@ static inline bool ptlock_init(struct ptdesc *ptdesc) return true; } -#else /* !USE_SPLIT_PTE_PTLOCKS */ +#else /* !defined(CONFIG_SPLIT_PTE_PTLOCKS) */ /* * We use mm->page_table_lock to guard all pagetable pages of the mm. */ @@ -2964,7 +2964,7 @@ static inline spinlock_t *ptep_lockptr(struct mm_struct *mm, pte_t *pte) static inline void ptlock_cache_init(void) {} static inline bool ptlock_init(struct ptdesc *ptdesc) { return true; } static inline void ptlock_free(struct ptdesc *ptdesc) {} -#endif /* USE_SPLIT_PTE_PTLOCKS */ +#endif /* defined(CONFIG_SPLIT_PTE_PTLOCKS) */ static inline bool pagetable_pte_ctor(struct ptdesc *ptdesc) { @@ -3024,7 +3024,7 @@ pte_t *pte_offset_map_nolock(struct mm_struct *mm, pmd_t *pmd, ((unlikely(pmd_none(*(pmd))) && __pte_alloc_kernel(pmd))? \ NULL: pte_offset_kernel(pmd, address)) -#if USE_SPLIT_PMD_PTLOCKS +#if defined(CONFIG_SPLIT_PMD_PTLOCKS) static inline struct page *pmd_pgtable_page(pmd_t *pmd) { diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 485424979254..165c58b12ccc 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -947,7 +947,7 @@ struct mm_struct { #ifdef CONFIG_MMU_NOTIFIER struct mmu_notifier_subscriptions *notifier_subscriptions; #endif -#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !defined(CONFIG_SPLIT_PMD_PTLOCKS) pgtable_t pmd_huge_pte; /* protected by page_table_lock */ #endif #ifdef CONFIG_NUMA_BALANCING diff --git a/include/linux/mm_types_task.h b/include/linux/mm_types_task.h index a2f6179b672b..bff5706b76e1 100644 --- a/include/linux/mm_types_task.h +++ b/include/linux/mm_types_task.h @@ -16,9 +16,6 @@ #include #endif -#define USE_SPLIT_PTE_PTLOCKS (NR_CPUS >= CONFIG_SPLIT_PTLOCK_CPUS) -#define USE_SPLIT_PMD_PTLOCKS (USE_SPLIT_PTE_PTLOCKS && \ - IS_ENABLED(CONFIG_ARCH_ENABLE_SPLIT_PMD_PTLOCK)) #define ALLOC_SPLIT_PTLOCKS (SPINLOCK_SIZE > BITS_PER_LONG/8) /* diff --git a/kernel/fork.c b/kernel/fork.c index cc760491f201..3d590e51ce84 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -832,7 +832,7 @@ static void check_mm(struct mm_struct *mm) pr_alert("BUG: non-zero pgtables_bytes on freeing mm: %ld\n", mm_pgtables_bytes(mm)); -#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !defined(CONFIG_SPLIT_PMD_PTLOCKS) VM_BUG_ON_MM(mm->pmd_huge_pte, mm); #endif } @@ -1276,7 +1276,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p, RCU_INIT_POINTER(mm->exe_file, NULL); mmu_notifier_subscriptions_init(mm); init_tlb_flush_pending(mm); -#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !USE_SPLIT_PMD_PTLOCKS +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && !defined(CONFIG_SPLIT_PMD_PTLOCKS) mm->pmd_huge_pte = NULL; #endif mm_init_uprobes_state(mm); diff --git a/mm/Kconfig b/mm/Kconfig index b72e7d040f78..7b716ac80272 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -585,17 +585,21 @@ config ARCH_MHP_MEMMAP_ON_MEMORY_ENABLE # at the same time (e.g. copy_page_range()). # DEBUG_SPINLOCK and DEBUG_LOCK_ALLOC spinlock_t also enlarge struct page. # -config SPLIT_PTLOCK_CPUS - int - default "999999" if !MMU - default "999999" if ARM && !CPU_CACHE_VIPT - default "999999" if PARISC && !PA20 - default "999999" if SPARC32 - default "4" +config SPLIT_PTE_PTLOCKS + def_bool y + depends on MMU + depends on NR_CPUS >= 4 + depends on !ARM || CPU_CACHE_VIPT + depends on !PARISC || PA20 + depends on !SPARC32 config ARCH_ENABLE_SPLIT_PMD_PTLOCK bool +config SPLIT_PMD_PTLOCKS + def_bool y + depends on SPLIT_PTE_PTLOCKS && ARCH_ENABLE_SPLIT_PMD_PTLOCK + # # support for memory balloon config MEMORY_BALLOON diff --git a/mm/memory.c b/mm/memory.c index a3d955098a19..71236ae6fd14 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -6571,7 +6571,7 @@ long copy_folio_from_user(struct folio *dst_folio, } #endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */ -#if USE_SPLIT_PTE_PTLOCKS && ALLOC_SPLIT_PTLOCKS +#if defined(CONFIG_SPLIT_PTE_PTLOCKS) && ALLOC_SPLIT_PTLOCKS static struct kmem_cache *page_ptl_cachep;