From c035713998700e8843c7d087f55bce3c54c0e3ec Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Fri, 5 Nov 2021 10:19:05 -0400 Subject: mm: Add functions to zero portions of a folio These functions are wrappers around zero_user_segments(), which means that zero_user_segments() can now be called for compound pages even when CONFIG_TRANSPARENT_HUGEPAGE is disabled. Use 'xend' as the name of the parameter to indicate that this is an excluded end, not the more usual included end. Excluding the end makes more sense to the callers, but can cause confusion to readers who are more used to seeing included ends. Signed-off-by: Matthew Wilcox (Oracle) Reviewed-by: Christoph Hellwig Reviewed-by: Darrick J. Wong --- mm/highmem.c | 2 -- 1 file changed, 2 deletions(-) (limited to 'mm/highmem.c') diff --git a/mm/highmem.c b/mm/highmem.c index 88f65f155845..819d41140e5b 100644 --- a/mm/highmem.c +++ b/mm/highmem.c @@ -359,7 +359,6 @@ void kunmap_high(struct page *page) } EXPORT_SYMBOL(kunmap_high); -#ifdef CONFIG_TRANSPARENT_HUGEPAGE void zero_user_segments(struct page *page, unsigned start1, unsigned end1, unsigned start2, unsigned end2) { @@ -416,7 +415,6 @@ void zero_user_segments(struct page *page, unsigned start1, unsigned end1, BUG_ON((start1 | start2 | end1 | end2) != 0); } EXPORT_SYMBOL(zero_user_segments); -#endif /* CONFIG_TRANSPARENT_HUGEPAGE */ #endif /* CONFIG_HIGHMEM */ #ifdef CONFIG_KMAP_LOCAL -- cgit v1.2.3-58-ga151 From 825c43f50e3aa811a291ffcb40e02fbf6d91ba86 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Fri, 19 Nov 2021 16:43:55 -0800 Subject: kmap_local: don't assume kmap PTEs are linear arrays in memory The kmap_local conversion broke the ARM architecture, because the new code assumes that all PTEs used for creating kmaps form a linear array in memory, and uses array indexing to look up the kmap PTE belonging to a certain kmap index. On ARM, this cannot work, not only because the PTE pages may be non-adjacent in memory, but also because ARM/!LPAE interleaves hardware entries and extended entries (carrying software-only bits) in a way that is not compatible with array indexing. Fortunately, this only seems to affect configurations with more than 8 CPUs, due to the way the per-CPU kmap slots are organized in memory. Work around this by permitting an architecture to set a Kconfig symbol that signifies that the kmap PTEs do not form a lineary array in memory, and so the only way to locate the appropriate one is to walk the page tables. Link: https://lore.kernel.org/linux-arm-kernel/20211026131249.3731275-1-ardb@kernel.org/ Link: https://lkml.kernel.org/r/20211116094737.7391-1-ardb@kernel.org Fixes: 2a15ba82fa6c ("ARM: highmem: Switch to generic kmap atomic") Signed-off-by: Ard Biesheuvel Reported-by: Quanyang Wang Reviewed-by: Linus Walleij Acked-by: Russell King (Oracle) Cc: Thomas Gleixner Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/arm/Kconfig | 1 + mm/Kconfig | 3 +++ mm/highmem.c | 32 +++++++++++++++++++++----------- 3 files changed, 25 insertions(+), 11 deletions(-) (limited to 'mm/highmem.c') diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index f0f9e8bec83a..c2724d986fa0 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -1463,6 +1463,7 @@ config HIGHMEM bool "High Memory Support" depends on MMU select KMAP_LOCAL + select KMAP_LOCAL_NON_LINEAR_PTE_ARRAY help The address space of ARM processors is only 4 Gigabytes large and it has to accommodate user address space, kernel address diff --git a/mm/Kconfig b/mm/Kconfig index 068ce591a13a..28edafc820ad 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -890,6 +890,9 @@ config MAPPING_DIRTY_HELPERS config KMAP_LOCAL bool +config KMAP_LOCAL_NON_LINEAR_PTE_ARRAY + bool + # struct io_mapping based helper. Selected by drivers that need them config IO_MAPPING bool diff --git a/mm/highmem.c b/mm/highmem.c index 88f65f155845..ca9fa8c92593 100644 --- a/mm/highmem.c +++ b/mm/highmem.c @@ -503,16 +503,22 @@ static inline int kmap_local_calc_idx(int idx) static pte_t *__kmap_pte; -static pte_t *kmap_get_pte(void) +static pte_t *kmap_get_pte(unsigned long vaddr, int idx) { + if (IS_ENABLED(CONFIG_KMAP_LOCAL_NON_LINEAR_PTE_ARRAY)) + /* + * Set by the arch if __kmap_pte[-idx] does not produce + * the correct entry. + */ + return virt_to_kpte(vaddr); if (!__kmap_pte) __kmap_pte = virt_to_kpte(__fix_to_virt(FIX_KMAP_BEGIN)); - return __kmap_pte; + return &__kmap_pte[-idx]; } void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot) { - pte_t pteval, *kmap_pte = kmap_get_pte(); + pte_t pteval, *kmap_pte; unsigned long vaddr; int idx; @@ -524,9 +530,10 @@ void *__kmap_local_pfn_prot(unsigned long pfn, pgprot_t prot) preempt_disable(); idx = arch_kmap_local_map_idx(kmap_local_idx_push(), pfn); vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx); - BUG_ON(!pte_none(*(kmap_pte - idx))); + kmap_pte = kmap_get_pte(vaddr, idx); + BUG_ON(!pte_none(*kmap_pte)); pteval = pfn_pte(pfn, prot); - arch_kmap_local_set_pte(&init_mm, vaddr, kmap_pte - idx, pteval); + arch_kmap_local_set_pte(&init_mm, vaddr, kmap_pte, pteval); arch_kmap_local_post_map(vaddr, pteval); current->kmap_ctrl.pteval[kmap_local_idx()] = pteval; preempt_enable(); @@ -559,7 +566,7 @@ EXPORT_SYMBOL(__kmap_local_page_prot); void kunmap_local_indexed(void *vaddr) { unsigned long addr = (unsigned long) vaddr & PAGE_MASK; - pte_t *kmap_pte = kmap_get_pte(); + pte_t *kmap_pte; int idx; if (addr < __fix_to_virt(FIX_KMAP_END) || @@ -584,8 +591,9 @@ void kunmap_local_indexed(void *vaddr) idx = arch_kmap_local_unmap_idx(kmap_local_idx(), addr); WARN_ON_ONCE(addr != __fix_to_virt(FIX_KMAP_BEGIN + idx)); + kmap_pte = kmap_get_pte(addr, idx); arch_kmap_local_pre_unmap(addr); - pte_clear(&init_mm, addr, kmap_pte - idx); + pte_clear(&init_mm, addr, kmap_pte); arch_kmap_local_post_unmap(addr); current->kmap_ctrl.pteval[kmap_local_idx()] = __pte(0); kmap_local_idx_pop(); @@ -607,7 +615,7 @@ EXPORT_SYMBOL(kunmap_local_indexed); void __kmap_local_sched_out(void) { struct task_struct *tsk = current; - pte_t *kmap_pte = kmap_get_pte(); + pte_t *kmap_pte; int i; /* Clear kmaps */ @@ -634,8 +642,9 @@ void __kmap_local_sched_out(void) idx = arch_kmap_local_map_idx(i, pte_pfn(pteval)); addr = __fix_to_virt(FIX_KMAP_BEGIN + idx); + kmap_pte = kmap_get_pte(addr, idx); arch_kmap_local_pre_unmap(addr); - pte_clear(&init_mm, addr, kmap_pte - idx); + pte_clear(&init_mm, addr, kmap_pte); arch_kmap_local_post_unmap(addr); } } @@ -643,7 +652,7 @@ void __kmap_local_sched_out(void) void __kmap_local_sched_in(void) { struct task_struct *tsk = current; - pte_t *kmap_pte = kmap_get_pte(); + pte_t *kmap_pte; int i; /* Restore kmaps */ @@ -663,7 +672,8 @@ void __kmap_local_sched_in(void) /* See comment in __kmap_local_sched_out() */ idx = arch_kmap_local_map_idx(i, pte_pfn(pteval)); addr = __fix_to_virt(FIX_KMAP_BEGIN + idx); - set_pte_at(&init_mm, addr, kmap_pte - idx, pteval); + kmap_pte = kmap_get_pte(addr, idx); + set_pte_at(&init_mm, addr, kmap_pte, pteval); arch_kmap_local_post_map(addr, pteval); } } -- cgit v1.2.3-58-ga151