On 15/01/2024 15:14, Alexandre Ghiti wrote: > Hi Ryan, > > On 18/12/2023 11:50, Ryan Roberts wrote: >> With the ptep API sufficiently refactored, we can now introduce a new >> "contpte" API layer, which transparently manages the PTE_CONT bit for >> user mappings. Whenever it detects a set of PTEs that meet the >> requirements for a contiguous range, the PTEs are re-painted with the >> PTE_CONT bit. Use of contpte mappings is intended to be transparent to >> the core-mm, which continues to interact with individual ptes. >> >> Since a contpte block only has a single access and dirty bit, the >> semantic here changes slightly; when getting a pte (e.g. ptep_get()) >> that is part of a contpte mapping, the access and dirty information are >> pulled from the block (so all ptes in the block return the same >> access/dirty info). When changing the access/dirty info on a pte (e.g. >> ptep_set_access_flags()) that is part of a contpte mapping, this change >> will affect the whole contpte block. This is works fine in practice >> since we guarantee that only a single folio is mapped by a contpte >> block, and the core-mm tracks access/dirty information per folio. >> >> This initial change provides a baseline that can be optimized in future >> commits. That said, fold/unfold operations (which imply tlb >> invalidation) are avoided where possible with a few tricks for >> access/dirty bit management. Write-protect modifications for contpte >> mappings are currently non-optimal, and incure a regression in fork() >> performance. This will be addressed in follow-up changes. >> >> In order for the public functions, which used to be pure inline, to >> continue to be callable by modules, export all the contpte_* symbols >> that are now called by those public inline functions. >> >> The feature is enabled/disabled with the ARM64_CONTPTE Kconfig parameter >> at build time. It defaults to enabled as long as its dependency, >> TRANSPARENT_HUGEPAGE is also enabled. The core-mm depends upon >> TRANSPARENT_HUGEPAGE to be able to allocate large folios, so if its not >> enabled, then there is no chance of meeting the physical contiguity >> requirement for contpte mappings. >> >> Tested-by: John Hubbard <jhubbard@xxxxxxxxxx> >> Signed-off-by: Ryan Roberts <ryan.roberts@xxxxxxx> >> --- >> arch/arm64/Kconfig | 10 +- >> arch/arm64/include/asm/pgtable.h | 184 +++++++++++++++ >> arch/arm64/mm/Makefile | 1 + >> arch/arm64/mm/contpte.c | 388 +++++++++++++++++++++++++++++++ >> 4 files changed, 582 insertions(+), 1 deletion(-) >> create mode 100644 arch/arm64/mm/contpte.c >> >> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig >> index 7b071a00425d..de76e484ff3a 100644 >> --- a/arch/arm64/Kconfig >> +++ b/arch/arm64/Kconfig >> @@ -2209,6 +2209,15 @@ config UNWIND_PATCH_PAC_INTO_SCS >> select UNWIND_TABLES >> select DYNAMIC_SCS >> +config ARM64_CONTPTE >> + bool "Contiguous PTE mappings for user memory" if EXPERT >> + depends on TRANSPARENT_HUGEPAGE >> + default y >> + help >> + When enabled, user mappings are configured using the PTE contiguous >> + bit, for any mappings that meet the size and alignment requirements. >> + This reduces TLB pressure and improves performance. >> + >> endmenu # "Kernel Features" >> menu "Boot options" >> @@ -2318,4 +2327,3 @@ endmenu # "CPU Power Management" >> source "drivers/acpi/Kconfig" >> source "arch/arm64/kvm/Kconfig" >> - >> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h >> index 6930c14f062f..e64120452301 100644 >> --- a/arch/arm64/include/asm/pgtable.h >> +++ b/arch/arm64/include/asm/pgtable.h >> @@ -133,6 +133,10 @@ static inline pteval_t __phys_to_pte_val(phys_addr_t phys) >> */ >> #define pte_valid_not_user(pte) \ >> ((pte_val(pte) & (PTE_VALID | PTE_USER | PTE_UXN)) == (PTE_VALID | >> PTE_UXN)) >> +/* >> + * Returns true if the pte is valid and has the contiguous bit set. >> + */ >> +#define pte_valid_cont(pte) (pte_valid(pte) && pte_cont(pte)) >> /* >> * Could the pte be present in the TLB? We must check mm_tlb_flush_pending >> * so that we don't erroneously return false for pages that have been >> @@ -1116,6 +1120,184 @@ extern void ptep_modify_prot_commit(struct >> vm_area_struct *vma, >> unsigned long addr, pte_t *ptep, >> pte_t old_pte, pte_t new_pte); >> +#ifdef CONFIG_ARM64_CONTPTE >> + >> +/* >> + * The contpte APIs are used to transparently manage the contiguous bit in ptes >> + * where it is possible and makes sense to do so. The PTE_CONT bit is considered >> + * a private implementation detail of the public ptep API (see below). >> + */ >> +extern void __contpte_try_fold(struct mm_struct *mm, unsigned long addr, >> + pte_t *ptep, pte_t pte); >> +extern void __contpte_try_unfold(struct mm_struct *mm, unsigned long addr, >> + pte_t *ptep, pte_t pte); >> +extern pte_t contpte_ptep_get(pte_t *ptep, pte_t orig_pte); >> +extern pte_t contpte_ptep_get_lockless(pte_t *orig_ptep); >> +extern void contpte_set_ptes(struct mm_struct *mm, unsigned long addr, >> + pte_t *ptep, pte_t pte, unsigned int nr); >> +extern int contpte_ptep_test_and_clear_young(struct vm_area_struct *vma, >> + unsigned long addr, pte_t *ptep); >> +extern int contpte_ptep_clear_flush_young(struct vm_area_struct *vma, >> + unsigned long addr, pte_t *ptep); >> +extern int contpte_ptep_set_access_flags(struct vm_area_struct *vma, >> + unsigned long addr, pte_t *ptep, >> + pte_t entry, int dirty); >> + >> +static inline void contpte_try_fold(struct mm_struct *mm, unsigned long addr, >> + pte_t *ptep, pte_t pte) >> +{ >> + /* >> + * Only bother trying if both the virtual and physical addresses are >> + * aligned and correspond to the last entry in a contig range. The core >> + * code mostly modifies ranges from low to high, so this is the likely >> + * the last modification in the contig range, so a good time to fold. >> + * We can't fold special mappings, because there is no associated folio. >> + */ >> + >> + const unsigned long contmask = CONT_PTES - 1; >> + bool valign = (((unsigned long)ptep >> 3) & contmask) == contmask; >> + bool palign = (pte_pfn(pte) & contmask) == contmask; >> + >> + if (valign && palign && >> + pte_valid(pte) && !pte_cont(pte) && !pte_special(pte)) >> + __contpte_try_fold(mm, addr, ptep, pte); >> +} >> + >> +static inline void contpte_try_unfold(struct mm_struct *mm, unsigned long addr, >> + pte_t *ptep, pte_t pte) >> +{ >> + if (pte_valid_cont(pte)) >> + __contpte_try_unfold(mm, addr, ptep, pte); >> +} >> + >> +/* >> + * The below functions constitute the public API that arm64 presents to the >> + * core-mm to manipulate PTE entries within their page tables (or at least this >> + * is the subset of the API that arm64 needs to implement). These public >> + * versions will automatically and transparently apply the contiguous bit where >> + * it makes sense to do so. Therefore any users that are contig-aware (e.g. >> + * hugetlb, kernel mapper) should NOT use these APIs, but instead use the >> + * private versions, which are prefixed with double underscore. All of these >> + * APIs except for ptep_get_lockless() are expected to be called with the PTL >> + * held. >> + */ >> + >> +#define ptep_get ptep_get >> +static inline pte_t ptep_get(pte_t *ptep) >> +{ >> + pte_t pte = __ptep_get(ptep); >> + >> + if (!pte_valid_cont(pte)) >> + return pte; >> + >> + return contpte_ptep_get(ptep, pte); >> +} >> + >> +#define ptep_get_lockless ptep_get_lockless >> +static inline pte_t ptep_get_lockless(pte_t *ptep) >> +{ >> + pte_t pte = __ptep_get(ptep); >> + >> + if (!pte_valid_cont(pte)) >> + return pte; >> + >> + return contpte_ptep_get_lockless(ptep); >> +} >> + >> +static inline void set_pte(pte_t *ptep, pte_t pte) >> +{ >> + /* >> + * We don't have the mm or vaddr so cannot unfold or fold contig entries >> + * (since it requires tlb maintenance). set_pte() is not used in core >> + * code, so this should never even be called. Regardless do our best to >> + * service any call and emit a warning if there is any attempt to set a >> + * pte on top of an existing contig range. >> + */ >> + pte_t orig_pte = __ptep_get(ptep); >> + >> + WARN_ON_ONCE(pte_valid_cont(orig_pte)); >> + __set_pte(ptep, pte_mknoncont(pte)); >> +} >> + >> +#define set_ptes set_ptes >> +static inline void set_ptes(struct mm_struct *mm, unsigned long addr, >> + pte_t *ptep, pte_t pte, unsigned int nr) >> +{ >> + pte = pte_mknoncont(pte); >> + >> + if (nr == 1) { >> + contpte_try_unfold(mm, addr, ptep, __ptep_get(ptep)); >> + __set_ptes(mm, addr, ptep, pte, 1); >> + contpte_try_fold(mm, addr, ptep, pte); >> + } else >> + contpte_set_ptes(mm, addr, ptep, pte, nr); >> +} >> + >> +static inline void pte_clear(struct mm_struct *mm, >> + unsigned long addr, pte_t *ptep) >> +{ >> + contpte_try_unfold(mm, addr, ptep, __ptep_get(ptep)); >> + __pte_clear(mm, addr, ptep); >> +} >> + >> +#define __HAVE_ARCH_PTEP_GET_AND_CLEAR >> +static inline pte_t ptep_get_and_clear(struct mm_struct *mm, >> + unsigned long addr, pte_t *ptep) >> +{ >> + contpte_try_unfold(mm, addr, ptep, __ptep_get(ptep)); >> + return __ptep_get_and_clear(mm, addr, ptep); >> +} >> + >> +#define __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG >> +static inline int ptep_test_and_clear_young(struct vm_area_struct *vma, >> + unsigned long addr, pte_t *ptep) >> +{ >> + pte_t orig_pte = __ptep_get(ptep); >> + >> + if (!pte_valid_cont(orig_pte)) >> + return __ptep_test_and_clear_young(vma, addr, ptep); >> + >> + return contpte_ptep_test_and_clear_young(vma, addr, ptep); >> +} >> + >> +#define __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH >> +static inline int ptep_clear_flush_young(struct vm_area_struct *vma, >> + unsigned long addr, pte_t *ptep) >> +{ >> + pte_t orig_pte = __ptep_get(ptep); >> + >> + if (!pte_valid_cont(orig_pte)) >> + return __ptep_clear_flush_young(vma, addr, ptep); >> + >> + return contpte_ptep_clear_flush_young(vma, addr, ptep); >> +} >> + >> +#define __HAVE_ARCH_PTEP_SET_WRPROTECT >> +static inline void ptep_set_wrprotect(struct mm_struct *mm, >> + unsigned long addr, pte_t *ptep) >> +{ >> + contpte_try_unfold(mm, addr, ptep, __ptep_get(ptep)); >> + __ptep_set_wrprotect(mm, addr, ptep); >> + contpte_try_fold(mm, addr, ptep, __ptep_get(ptep)); >> +} >> + >> +#define __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS >> +static inline int ptep_set_access_flags(struct vm_area_struct *vma, >> + unsigned long addr, pte_t *ptep, >> + pte_t entry, int dirty) >> +{ >> + pte_t orig_pte = __ptep_get(ptep); >> + >> + entry = pte_mknoncont(entry); >> + >> + if (!pte_valid_cont(orig_pte)) >> + return __ptep_set_access_flags(vma, addr, ptep, entry, dirty); >> + >> + return contpte_ptep_set_access_flags(vma, addr, ptep, entry, dirty); >> +} >> + >> +#else /* CONFIG_ARM64_CONTPTE */ >> + >> #define ptep_get __ptep_get >> #define set_pte __set_pte >> #define set_ptes __set_ptes >> @@ -1131,6 +1313,8 @@ extern void ptep_modify_prot_commit(struct >> vm_area_struct *vma, >> #define __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS >> #define ptep_set_access_flags __ptep_set_access_flags >> +#endif /* CONFIG_ARM64_CONTPTE */ >> + >> #endif /* !__ASSEMBLY__ */ >> #endif /* __ASM_PGTABLE_H */ >> diff --git a/arch/arm64/mm/Makefile b/arch/arm64/mm/Makefile >> index dbd1bc95967d..60454256945b 100644 >> --- a/arch/arm64/mm/Makefile >> +++ b/arch/arm64/mm/Makefile >> @@ -3,6 +3,7 @@ obj-y := dma-mapping.o extable.o fault.o init.o \ >> cache.o copypage.o flush.o \ >> ioremap.o mmap.o pgd.o mmu.o \ >> context.o proc.o pageattr.o fixmap.o >> +obj-$(CONFIG_ARM64_CONTPTE) += contpte.o >> obj-$(CONFIG_HUGETLB_PAGE) += hugetlbpage.o >> obj-$(CONFIG_PTDUMP_CORE) += ptdump.o >> obj-$(CONFIG_PTDUMP_DEBUGFS) += ptdump_debugfs.o >> diff --git a/arch/arm64/mm/contpte.c b/arch/arm64/mm/contpte.c >> new file mode 100644 >> index 000000000000..69c36749dd98 >> --- /dev/null >> +++ b/arch/arm64/mm/contpte.c >> @@ -0,0 +1,388 @@ >> +// SPDX-License-Identifier: GPL-2.0-only >> +/* >> + * Copyright (C) 2023 ARM Ltd. >> + */ >> + >> +#include <linux/mm.h> >> +#include <linux/export.h> >> +#include <asm/tlbflush.h> >> + >> +static inline bool mm_is_user(struct mm_struct *mm) >> +{ >> + /* >> + * Don't attempt to apply the contig bit to kernel mappings, because >> + * dynamically adding/removing the contig bit can cause page faults. >> + * These racing faults are ok for user space, since they get serialized >> + * on the PTL. But kernel mappings can't tolerate faults. >> + */ >> + return mm != &init_mm; >> +} >> + >> +static inline pte_t *contpte_align_down(pte_t *ptep) >> +{ >> + return (pte_t *)(ALIGN_DOWN((unsigned long)ptep >> 3, CONT_PTES) << 3); >> +} >> + >> +static void ptep_clear_flush_range(struct mm_struct *mm, unsigned long addr, >> + pte_t *ptep, int nr) >> +{ >> + struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0); >> + unsigned long start_addr = addr; >> + int i; >> + >> + for (i = 0; i < nr; i++, ptep++, addr += PAGE_SIZE) >> + __pte_clear(mm, addr, ptep); >> + >> + __flush_tlb_range(&vma, start_addr, addr, PAGE_SIZE, true, 3); >> +} >> + >> +static bool ptep_any_valid(pte_t *ptep, int nr) >> +{ >> + int i; >> + >> + for (i = 0; i < nr; i++, ptep++) { >> + if (pte_valid(__ptep_get(ptep))) >> + return true; >> + } >> + >> + return false; >> +} >> + >> +static void contpte_convert(struct mm_struct *mm, unsigned long addr, >> + pte_t *ptep, pte_t pte) >> +{ >> + struct vm_area_struct vma = TLB_FLUSH_VMA(mm, 0); >> + unsigned long start_addr; >> + pte_t *start_ptep; >> + int i; >> + >> + start_ptep = ptep = contpte_align_down(ptep); >> + start_addr = addr = ALIGN_DOWN(addr, CONT_PTE_SIZE); >> + pte = pfn_pte(ALIGN_DOWN(pte_pfn(pte), CONT_PTES), pte_pgprot(pte)); >> + >> + for (i = 0; i < CONT_PTES; i++, ptep++, addr += PAGE_SIZE) { >> + pte_t ptent = __ptep_get_and_clear(mm, addr, ptep); >> + >> + if (pte_dirty(ptent)) >> + pte = pte_mkdirty(pte); >> + >> + if (pte_young(ptent)) >> + pte = pte_mkyoung(pte); >> + } >> + >> + __flush_tlb_range(&vma, start_addr, addr, PAGE_SIZE, true, 3); >> + >> + __set_ptes(mm, start_addr, start_ptep, pte, CONT_PTES); >> +} >> + >> +void __contpte_try_fold(struct mm_struct *mm, unsigned long addr, >> + pte_t *ptep, pte_t pte) >> +{ >> + /* >> + * We have already checked that the virtual and pysical addresses are >> + * correctly aligned for a contpte mapping in contpte_try_fold() so the >> + * remaining checks are to ensure that the contpte range is fully >> + * covered by a single folio, and ensure that all the ptes are valid >> + * with contiguous PFNs and matching prots. We ignore the state of the >> + * access and dirty bits for the purpose of deciding if its a contiguous >> + * range; the folding process will generate a single contpte entry which >> + * has a single access and dirty bit. Those 2 bits are the logical OR of >> + * their respective bits in the constituent pte entries. In order to >> + * ensure the contpte range is covered by a single folio, we must >> + * recover the folio from the pfn, but special mappings don't have a >> + * folio backing them. Fortunately contpte_try_fold() already checked >> + * that the pte is not special - we never try to fold special mappings. >> + * Note we can't use vm_normal_page() for this since we don't have the >> + * vma. >> + */ >> + >> + unsigned long folio_saddr; >> + unsigned long folio_eaddr; >> + unsigned long cont_saddr; >> + unsigned long cont_eaddr; >> + struct folio *folio; >> + struct page *page; >> + unsigned long pfn; >> + pte_t *orig_ptep; >> + pgprot_t prot; >> + pte_t subpte; >> + int i; >> + >> + if (!mm_is_user(mm)) >> + return; >> + >> + page = pte_page(pte); >> + folio = page_folio(page); >> + folio_saddr = addr - (page - &folio->page) * PAGE_SIZE; >> + folio_eaddr = folio_saddr + folio_nr_pages(folio) * PAGE_SIZE; >> + cont_saddr = ALIGN_DOWN(addr, CONT_PTE_SIZE); >> + cont_eaddr = cont_saddr + CONT_PTE_SIZE; >> + >> + if (folio_saddr > cont_saddr || folio_eaddr < cont_eaddr) >> + return; >> + >> + pfn = pte_pfn(pte) - ((addr - cont_saddr) >> PAGE_SHIFT); >> + prot = pte_pgprot(pte_mkold(pte_mkclean(pte))); >> + orig_ptep = ptep; >> + ptep = contpte_align_down(ptep); >> + >> + for (i = 0; i < CONT_PTES; i++, ptep++, pfn++) { >> + subpte = __ptep_get(ptep); >> + subpte = pte_mkold(pte_mkclean(subpte)); >> + >> + if (!pte_valid(subpte) || >> + pte_pfn(subpte) != pfn || >> + pgprot_val(pte_pgprot(subpte)) != pgprot_val(prot)) >> + return; >> + } >> + >> + pte = pte_mkcont(pte); >> + contpte_convert(mm, addr, orig_ptep, pte); >> +} >> +EXPORT_SYMBOL(__contpte_try_fold); >> + >> +void __contpte_try_unfold(struct mm_struct *mm, unsigned long addr, >> + pte_t *ptep, pte_t pte) >> +{ >> + /* >> + * We have already checked that the ptes are contiguous in >> + * contpte_try_unfold(), so just check that the mm is user space. >> + */ >> + >> + if (!mm_is_user(mm)) >> + return; >> + >> + pte = pte_mknoncont(pte); >> + contpte_convert(mm, addr, ptep, pte); >> +} >> +EXPORT_SYMBOL(__contpte_try_unfold); >> + >> +pte_t contpte_ptep_get(pte_t *ptep, pte_t orig_pte) >> +{ >> + /* >> + * Gather access/dirty bits, which may be populated in any of the ptes >> + * of the contig range. We are guarranteed to be holding the PTL, so any >> + * contiguous range cannot be unfolded or otherwise modified under our >> + * feet. >> + */ >> + >> + pte_t pte; >> + int i; >> + >> + ptep = contpte_align_down(ptep); >> + >> + for (i = 0; i < CONT_PTES; i++, ptep++) { >> + pte = __ptep_get(ptep); >> + >> + if (pte_dirty(pte)) >> + orig_pte = pte_mkdirty(orig_pte); >> + >> + if (pte_young(pte)) >> + orig_pte = pte_mkyoung(orig_pte); >> + } >> + >> + return orig_pte; >> +} >> +EXPORT_SYMBOL(contpte_ptep_get); >> + >> +pte_t contpte_ptep_get_lockless(pte_t *orig_ptep) >> +{ >> + /* >> + * Gather access/dirty bits, which may be populated in any of the ptes >> + * of the contig range. We may not be holding the PTL, so any contiguous >> + * range may be unfolded/modified/refolded under our feet. Therefore we >> + * ensure we read a _consistent_ contpte range by checking that all ptes >> + * in the range are valid and have CONT_PTE set, that all pfns are >> + * contiguous and that all pgprots are the same (ignoring access/dirty). >> + * If we find a pte that is not consistent, then we must be racing with >> + * an update so start again. If the target pte does not have CONT_PTE >> + * set then that is considered consistent on its own because it is not >> + * part of a contpte range. >> + */ >> + >> + pgprot_t orig_prot; >> + unsigned long pfn; >> + pte_t orig_pte; >> + pgprot_t prot; >> + pte_t *ptep; >> + pte_t pte; >> + int i; >> + >> +retry: >> + orig_pte = __ptep_get(orig_ptep); >> + >> + if (!pte_valid_cont(orig_pte)) >> + return orig_pte; >> + >> + orig_prot = pte_pgprot(pte_mkold(pte_mkclean(orig_pte))); >> + ptep = contpte_align_down(orig_ptep); >> + pfn = pte_pfn(orig_pte) - (orig_ptep - ptep); >> + >> + for (i = 0; i < CONT_PTES; i++, ptep++, pfn++) { >> + pte = __ptep_get(ptep); >> + prot = pte_pgprot(pte_mkold(pte_mkclean(pte))); >> + >> + if (!pte_valid_cont(pte) || >> + pte_pfn(pte) != pfn || >> + pgprot_val(prot) != pgprot_val(orig_prot)) >> + goto retry; >> + >> + if (pte_dirty(pte)) >> + orig_pte = pte_mkdirty(orig_pte); >> + >> + if (pte_young(pte)) >> + orig_pte = pte_mkyoung(orig_pte); >> + } >> + >> + return orig_pte; >> +} >> +EXPORT_SYMBOL(contpte_ptep_get_lockless); >> + >> +void contpte_set_ptes(struct mm_struct *mm, unsigned long addr, >> + pte_t *ptep, pte_t pte, unsigned int nr) >> +{ >> + unsigned long next; >> + unsigned long end; >> + unsigned long pfn; >> + pgprot_t prot; >> + pte_t orig_pte; >> + >> + if (!mm_is_user(mm)) >> + return __set_ptes(mm, addr, ptep, pte, nr); >> + >> + end = addr + (nr << PAGE_SHIFT); >> + pfn = pte_pfn(pte); >> + prot = pte_pgprot(pte); >> + >> + do { >> + next = pte_cont_addr_end(addr, end); >> + nr = (next - addr) >> PAGE_SHIFT; >> + pte = pfn_pte(pfn, prot); >> + >> + if (((addr | next | (pfn << PAGE_SHIFT)) & ~CONT_PTE_MASK) == 0) >> + pte = pte_mkcont(pte); >> + else >> + pte = pte_mknoncont(pte); >> + >> + /* >> + * If operating on a partial contiguous range then we must first >> + * unfold the contiguous range if it was previously folded. >> + * Otherwise we could end up with overlapping tlb entries. >> + */ >> + if (nr != CONT_PTES) >> + contpte_try_unfold(mm, addr, ptep, __ptep_get(ptep)); >> + >> + /* >> + * If we are replacing ptes that were contiguous or if the new >> + * ptes are contiguous and any of the ptes being replaced are >> + * valid, we need to clear and flush the range to prevent >> + * overlapping tlb entries. >> + */ >> + orig_pte = __ptep_get(ptep); >> + if (pte_valid_cont(orig_pte) || >> + (pte_cont(pte) && ptep_any_valid(ptep, nr))) >> + ptep_clear_flush_range(mm, addr, ptep, nr); >> + >> + __set_ptes(mm, addr, ptep, pte, nr); >> + >> + addr = next; >> + ptep += nr; >> + pfn += nr; >> + >> + } while (addr != end); >> +} >> +EXPORT_SYMBOL(contpte_set_ptes); >> + >> +int contpte_ptep_test_and_clear_young(struct vm_area_struct *vma, >> + unsigned long addr, pte_t *ptep) >> +{ >> + /* >> + * ptep_clear_flush_young() technically requires us to clear the access >> + * flag for a _single_ pte. However, the core-mm code actually tracks >> + * access/dirty per folio, not per page. And since we only create a >> + * contig range when the range is covered by a single folio, we can get >> + * away with clearing young for the whole contig range here, so we avoid >> + * having to unfold. >> + */ >> + >> + int young = 0; >> + int i; >> + >> + ptep = contpte_align_down(ptep); >> + addr = ALIGN_DOWN(addr, CONT_PTE_SIZE); >> + >> + for (i = 0; i < CONT_PTES; i++, ptep++, addr += PAGE_SIZE) >> + young |= __ptep_test_and_clear_young(vma, addr, ptep); >> + >> + return young; >> +} >> +EXPORT_SYMBOL(contpte_ptep_test_and_clear_young); >> + >> +int contpte_ptep_clear_flush_young(struct vm_area_struct *vma, >> + unsigned long addr, pte_t *ptep) >> +{ >> + int young; >> + >> + young = contpte_ptep_test_and_clear_young(vma, addr, ptep); >> + >> + if (young) { >> + /* >> + * See comment in __ptep_clear_flush_young(); same rationale for >> + * eliding the trailing DSB applies here. >> + */ >> + addr = ALIGN_DOWN(addr, CONT_PTE_SIZE); >> + __flush_tlb_range_nosync(vma, addr, addr + CONT_PTE_SIZE, >> + PAGE_SIZE, true, 3); >> + } >> + >> + return young; >> +} >> +EXPORT_SYMBOL(contpte_ptep_clear_flush_young); >> + >> +int contpte_ptep_set_access_flags(struct vm_area_struct *vma, >> + unsigned long addr, pte_t *ptep, >> + pte_t entry, int dirty) >> +{ >> + unsigned long start_addr; >> + pte_t orig_pte; >> + int i; >> + >> + /* >> + * Gather the access/dirty bits for the contiguous range. If nothing has >> + * changed, its a noop. >> + */ >> + orig_pte = pte_mknoncont(ptep_get(ptep)); >> + if (pte_val(orig_pte) == pte_val(entry)) >> + return 0; >> + >> + /* >> + * We can fix up access/dirty bits without having to unfold/fold the >> + * contig range. But if the write bit is changing, we need to go through >> + * the full unfold/fold cycle. >> + */ >> + if (pte_write(orig_pte) == pte_write(entry)) { >> + /* >> + * For HW access management, we technically only need to update >> + * the flag on a single pte in the range. But for SW access >> + * management, we need to update all the ptes to prevent extra >> + * faults. Avoid per-page tlb flush in __ptep_set_access_flags() >> + * and instead flush the whole range at the end. >> + */ >> + ptep = contpte_align_down(ptep); >> + start_addr = addr = ALIGN_DOWN(addr, CONT_PTE_SIZE); >> + >> + for (i = 0; i < CONT_PTES; i++, ptep++, addr += PAGE_SIZE) >> + __ptep_set_access_flags(vma, addr, ptep, entry, 0); > > > entry was pte_mknoncont() in ptep_set_access_flags() so here you lose the > contpte range, is that intentional? Or am I mistaken? entry doesn't have PTE_CONT bit set, that's correct. I intentionally strip that bit at the interface boundary, because it is the implementation's job to decide whether its a contpte block, not the caller's. But there are situations where the caller can end up with a pte that has PTE_CONT set (by having done a previous ptep_get() for example) and then it forwards the pte to a setter. So stripping it is required; It would probably be cleaner to strip it before returning it from ptep_get(), but that would be problematic for pte_leaf_size() which is called from perf_get_pgtable_size(). In this particular case, __ptep_set_access_flags() only modifies the PTE's access flags, so CONT_PTE will remain as it is in the page table. The fact that entry has it cleared is not a problem. Thanks, Ryan > > >> + >> + if (dirty) >> + __flush_tlb_range(vma, start_addr, addr, >> + PAGE_SIZE, true, 3); >> + } else { >> + __contpte_try_unfold(vma->vm_mm, addr, ptep, orig_pte); >> + __ptep_set_access_flags(vma, addr, ptep, entry, dirty); >> + contpte_try_fold(vma->vm_mm, addr, ptep, entry); >> + } >> + >> + return 1; >> +} >> +EXPORT_SYMBOL(contpte_ptep_set_access_flags);