[PATCH OLK-6.6 0/3] A Solution to Re-enable hugetlb vmemmap optimize
HVO was previously disabled on arm64 [1] due to the lack of necessary BBM(break-before-make) logic when changing page tables. This set of patches fix this by adding necessary BBM sequence when changing page table, and supporting vmemmap page fault handling to fixup kernel address translation fault if vmemmap is concurrently accessed. I have tested this patch set with concurrently accessing the vmemmap address when do BBM and can recover by vmemmap fault handler. Also tested under the config of 2/3/4 pgtable levels with 4K/64K page size and all works well. [1] commit 060a2c92d1b6 ("arm64: mm: hugetlb: Disable HUGETLB_PAGE_OPTIMIZE_VMEMMAP") Nanyong Sun (3): mm: HVO: introduce helper function to update and flush pgtable arm64: mm: HVO: support BBM of vmemmap pgtable safely arm64: mm: Re-enable OPTIMIZE_HUGETLB_VMEMMAP arch/arm64/Kconfig | 1 + arch/arm64/include/asm/esr.h | 4 ++ arch/arm64/include/asm/pgtable.h | 7 +++ arch/arm64/include/asm/tlbflush.h | 16 ++++++ arch/arm64/mm/fault.c | 94 +++++++++++++++++++++++++++++-- arch/arm64/mm/mmu.c | 28 +++++++++ mm/hugetlb_vmemmap.c | 51 +++++++++++++---- 7 files changed, 186 insertions(+), 15 deletions(-) -- 2.25.1
hulk inclusion category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I9JCV4 --------------------------- Add pmd/pte update and tlb flush helper function to update page table. This refactoring patch is designed to facilitate each architecture to implement its own special logic in preparation for the arm64 architecture to follow the necessary break-before-make sequence when updating page tables. Signed-off-by: Nanyong Sun <sunnanyong@huawei.com> Reviewed-by: Muchun Song <songmuchun@bytedance.com> --- mm/hugetlb_vmemmap.c | 47 ++++++++++++++++++++++++++++++++++++-------- 1 file changed, 39 insertions(+), 8 deletions(-) diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c index beaae51033db..b9466c141bbf 100644 --- a/mm/hugetlb_vmemmap.c +++ b/mm/hugetlb_vmemmap.c @@ -37,6 +37,37 @@ struct vmemmap_remap_walk { struct list_head *vmemmap_pages; }; +#ifndef vmemmap_update_pmd +static inline void vmemmap_update_pmd(unsigned long addr, + pmd_t *pmdp, pte_t *ptep) +{ + pmd_populate_kernel(&init_mm, pmdp, ptep); +} +#endif + +#ifndef vmemmap_update_pte +static inline void vmemmap_update_pte(unsigned long addr, + pte_t *ptep, pte_t pte) +{ + set_pte_at(&init_mm, addr, ptep, pte); +} +#endif + +#ifndef vmemmap_flush_tlb_all +static inline void vmemmap_flush_tlb_all(void) +{ + flush_tlb_all(); +} +#endif + +#ifndef vmemmap_flush_tlb_range +static inline void vmemmap_flush_tlb_range(unsigned long start, + unsigned long end) +{ + flush_tlb_kernel_range(start, end); +} +#endif + static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start) { pmd_t __pmd; @@ -79,8 +110,8 @@ static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start) /* Make pte visible before pmd. See comment in pmd_install(). */ smp_wmb(); - pmd_populate_kernel(&init_mm, pmd, pgtable); - flush_tlb_kernel_range(start, start + PMD_SIZE); + vmemmap_update_pmd(start, pmd, pgtable); + vmemmap_flush_tlb_range(start, start + PMD_SIZE); } else { pte_free_kernel(&init_mm, pgtable); } @@ -198,7 +229,7 @@ static int vmemmap_remap_range(unsigned long start, unsigned long end, return ret; } while (pgd++, addr = next, addr != end); - flush_tlb_kernel_range(start, end); + vmemmap_flush_tlb_range(start, end); return 0; } @@ -244,15 +275,15 @@ static void vmemmap_remap_pte(pte_t *pte, unsigned long addr, /* * Makes sure that preceding stores to the page contents from - * vmemmap_remap_free() become visible before the set_pte_at() - * write. + * vmemmap_remap_free() become visible before the + * vmemmap_update_pte() write. */ smp_wmb(); } entry = mk_pte(walk->reuse_page, pgprot); list_add_tail(&page->lru, walk->vmemmap_pages); - set_pte_at(&init_mm, addr, pte, entry); + vmemmap_update_pte(addr, pte, entry); } /* @@ -291,10 +322,10 @@ static void vmemmap_restore_pte(pte_t *pte, unsigned long addr, /* * Makes sure that preceding stores to the page contents become visible - * before the set_pte_at() write. + * before the vmemmap_update_pte() write. */ smp_wmb(); - set_pte_at(&init_mm, addr, pte, mk_pte(page, pgprot)); + vmemmap_update_pte(addr, pte, mk_pte(page, pgprot)); } /** -- 2.25.1
hulk inclusion category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I9JCV4 --------------------------- Implement vmemmap_update_pmd and vmemmap_update_pte on arm64 to do BBM(break-before-make) logic when change the page table of vmemmap address, they will under the init_mm.page_table_lock. If a translation fault of vmemmap address concurrently happened after pte/pmd cleared, vmemmap page fault handler will acquire the init_mm.page_table_lock to wait for vmemmap update to complete, by then the virtual address is valid again, so PF can return and access can continue. In other case, do the traditional kernel fault. Implement vmemmap_flush_tlb_all/range on arm64 with nothing to do because tlb already flushed in every single BBM. Signed-off-by: Nanyong Sun <sunnanyong@huawei.com> --- arch/arm64/include/asm/esr.h | 4 ++ arch/arm64/include/asm/pgtable.h | 7 +++ arch/arm64/include/asm/tlbflush.h | 16 ++++++ arch/arm64/mm/fault.c | 94 +++++++++++++++++++++++++++++-- arch/arm64/mm/mmu.c | 28 +++++++++ mm/hugetlb_vmemmap.c | 4 +- 6 files changed, 146 insertions(+), 7 deletions(-) diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h index ae35939f395b..1c63256efd25 100644 --- a/arch/arm64/include/asm/esr.h +++ b/arch/arm64/include/asm/esr.h @@ -116,6 +116,10 @@ #define ESR_ELx_FSC_SERROR (0x11) #define ESR_ELx_FSC_ACCESS (0x08) #define ESR_ELx_FSC_FAULT (0x04) +#define ESR_ELx_FSC_FAULT_L0 (0x04) +#define ESR_ELx_FSC_FAULT_L1 (0x05) +#define ESR_ELx_FSC_FAULT_L2 (0x06) +#define ESR_ELx_FSC_FAULT_L3 (0x07) #define ESR_ELx_FSC_PERM (0x0C) #define ESR_ELx_FSC_SEA_TTW0 (0x14) #define ESR_ELx_FSC_SEA_TTW1 (0x15) diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h index 401087e8a43d..b72196ed5a76 100644 --- a/arch/arm64/include/asm/pgtable.h +++ b/arch/arm64/include/asm/pgtable.h @@ -1453,6 +1453,13 @@ static inline int ptep_set_access_flags(struct vm_area_struct *vma, #endif /* CONFIG_ARM64_CONTPTE */ +#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP +void vmemmap_update_pmd(unsigned long addr, pmd_t *pmdp, pte_t *ptep); +#define vmemmap_update_pmd vmemmap_update_pmd +void vmemmap_update_pte(unsigned long addr, pte_t *ptep, pte_t pte); +#define vmemmap_update_pte vmemmap_update_pte +#endif + #endif /* !__ASSEMBLY__ */ #endif /* __ASM_PGTABLE_H */ diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h index 2e7a9b70ea6e..046bc64be6d0 100644 --- a/arch/arm64/include/asm/tlbflush.h +++ b/arch/arm64/include/asm/tlbflush.h @@ -488,6 +488,22 @@ static inline void __flush_tlb_kernel_pgtable(unsigned long kaddr) dsb(ish); isb(); } + +#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP +static inline void vmemmap_flush_tlb_all(void) +{ + /* do nothing, already flushed tlb in every single BBM */ +} +#define vmemmap_flush_tlb_all vmemmap_flush_tlb_all + +static inline void vmemmap_flush_tlb_range(unsigned long start, + unsigned long end) +{ + /* do nothing, already flushed tlb in every single BBM */ +} +#define vmemmap_flush_tlb_range vmemmap_flush_tlb_range +#endif + #endif #endif diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index 5d040bbfd247..4ea07caba71c 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -394,6 +394,85 @@ static bool is_el1_mte_sync_tag_check_fault(unsigned long esr) return false; } +#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP +static inline bool vmemmap_fault_may_fixup(unsigned long addr, + unsigned long esr) +{ + if (!static_branch_likely(&hugetlb_optimize_vmemmap_key)) + return false; + + if (addr < VMEMMAP_START || addr >= VMEMMAP_END) + return false; + + /* + * Only try to handle translation fault level 2 or level 3, + * because hugetlb vmemmap optimize only clear pmd or pte. + */ + switch (esr & ESR_ELx_FSC) { + case ESR_ELx_FSC_FAULT_L2: + case ESR_ELx_FSC_FAULT_L3: + return true; + default: + return false; + } +} + +/* + * PMD mapped vmemmap should has been split as PTE mapped + * by HVO now, here we only check this case, other cases + * should fail. + * Also should check the addr is healthy enough that will not cause + * a level2 or level3 translation fault again after page fault + * handled with success, so we need check both bits[1:0] of PMD and + * PTE as ARM Spec mentioned below: + * A Translation fault is generated if bits[1:0] of a translation + * table descriptor identify the descriptor as either a Fault + * encoding or a reserved encoding. + */ +static inline bool vmemmap_addr_healthy(unsigned long addr) +{ + pmd_t *pmdp, pmd; + pte_t *ptep, pte; + + pmdp = pmd_off_k(addr); + pmd = pmdp_get(pmdp); + if (!pmd_table(pmd)) + return false; + + ptep = pte_offset_kernel(pmdp, addr); + pte = ptep_get(ptep); + return (pte_val(pte) & PTE_TYPE_MASK) == PTE_TYPE_PAGE; +} + +static bool vmemmap_handle_page_fault(unsigned long addr, + unsigned long esr) +{ + bool ret; + unsigned long flags; + + if (likely(!vmemmap_fault_may_fixup(addr, esr))) + return false; + + spin_lock_irqsave(&init_mm.page_table_lock, flags); + ret = vmemmap_addr_healthy(addr); + spin_unlock_irqrestore(&init_mm.page_table_lock, flags); + + return ret; +} +#else +static inline bool vmemmap_fault_may_fixup(unsigned long addr, + unsigned long esr) +{ + return false; +} + +static inline bool vmemmap_handle_page_fault(unsigned long addr, + unsigned long esr) +{ + return false; +} +#endif /* CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP */ + static bool is_translation_fault(unsigned long esr) { return (esr & ESR_ELx_FSC_TYPE) == ESR_ELx_FSC_FAULT; @@ -411,9 +490,11 @@ static void __do_kernel_fault(unsigned long addr, unsigned long esr, if (!is_el1_instruction_abort(esr) && fixup_exception(regs)) return; - if (WARN_RATELIMIT(is_spurious_el1_translation_fault(addr, esr, regs), - "Ignoring spurious kernel translation fault at virtual address %016lx\n", addr)) + if (is_spurious_el1_translation_fault(addr, esr, regs)) { + WARN_RATELIMIT(!vmemmap_fault_may_fixup(addr, esr), + "Ignoring spurious kernel translation fault at virtual address %016lx\n", addr); return; + } if (is_el1_mte_sync_tag_check_fault(esr)) { do_tag_recovery(addr, esr, regs); @@ -431,9 +512,12 @@ static void __do_kernel_fault(unsigned long addr, unsigned long esr, } else if (addr < PAGE_SIZE) { msg = "NULL pointer dereference"; } else { - if (is_translation_fault(esr) && - kfence_handle_page_fault(addr, esr & ESR_ELx_WNR, regs)) - return; + if (is_translation_fault(esr)) { + if (kfence_handle_page_fault(addr, esr & ESR_ELx_WNR, regs)) + return; + if (vmemmap_handle_page_fault(addr, esr)) + return; + } msg = "paging request"; } diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 84fb680f69ce..4142a75a414e 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -1151,6 +1151,34 @@ int __meminit vmemmap_check_pmd(pmd_t *pmdp, int node, return 1; } +#ifdef CONFIG_HUGETLB_PAGE_OPTIMIZE_VMEMMAP +/* + * In the window between the page table entry is cleared and filled + * with a new value, other threads have the opportunity to concurrently + * access the vmemmap area then page translation fault occur. + * Therefore, we need to ensure that the init_mm.page_table_lock is held + * to synchronize the vmemmap page fault handling which will wait for + * this lock to be released to ensure that the page table entry has been + * refreshed with a new valid value. + */ +void vmemmap_update_pmd(unsigned long addr, pmd_t *pmdp, pte_t *ptep) +{ + lockdep_assert_held(&init_mm.page_table_lock); + pmd_clear(pmdp); + flush_tlb_kernel_range(addr, addr + PMD_SIZE); + pmd_populate_kernel(&init_mm, pmdp, ptep); +} + +void vmemmap_update_pte(unsigned long addr, pte_t *ptep, pte_t pte) +{ + spin_lock_irq(&init_mm.page_table_lock); + pte_clear(&init_mm, addr, ptep); + flush_tlb_kernel_range(addr, addr + PAGE_SIZE); + set_pte_at(&init_mm, addr, ptep, pte); + spin_unlock_irq(&init_mm.page_table_lock); +} +#endif + int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node, struct vmem_altmap *altmap) { diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c index b9466c141bbf..fb0b05d4659a 100644 --- a/mm/hugetlb_vmemmap.c +++ b/mm/hugetlb_vmemmap.c @@ -98,7 +98,7 @@ static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start) set_pte_at(&init_mm, addr, pte, entry); } - spin_lock(&init_mm.page_table_lock); + spin_lock_irq(&init_mm.page_table_lock); if (likely(pmd_leaf(*pmd))) { /* * Higher order allocations from buddy allocator must be able to @@ -115,7 +115,7 @@ static int split_vmemmap_huge_pmd(pmd_t *pmd, unsigned long start) } else { pte_free_kernel(&init_mm, pgtable); } - spin_unlock(&init_mm.page_table_lock); + spin_unlock_irq(&init_mm.page_table_lock); return 0; } -- 2.25.1
hulk inclusion category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I9JCV4 --------------------------- Now update of vmemmap page table can follow the rule of break-before-make safely for arm64 architecture, re-enable HVO on arm64. Signed-off-by: Nanyong Sun <sunnanyong@huawei.com> Reviewed-by: Muchun Song <songmuchun@bytedance.com> --- arch/arm64/Kconfig | 1 + 1 file changed, 1 insertion(+) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 890461d3f5e5..2712d3c73719 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -104,6 +104,7 @@ config ARM64 select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT select ARCH_WANT_FRAME_POINTERS select ARCH_WANT_HUGE_PMD_SHARE if ARM64_4K_PAGES || (ARM64_16K_PAGES && !ARM64_VA_BITS_36) + select ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP if !PREEMPT_RT select ARCH_WANT_LD_ORPHAN_WARN select ARCH_WANTS_NO_INSTR select ARCH_WANTS_THP_SWAP if ARM64_4K_PAGES -- 2.25.1
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