Platforms like arm and arm64 have redefined pfn_valid() because their early memory sections might have contained memmap holes after freeing parts of it during boot, which should be skipped while validating a pfn for struct page backing. This scenario on certain platforms where memmap is not continuous, could be captured with a new option CONFIG_HAVE_EARLY_SECTION_MEMMAP_HOLES. Then the generic pfn_valid() can be improved to accommodate such platforms. This reduces overall code footprint and also improves maintainability. free_unused_memmap() and pfn_to_online_page() have been updated to include such cases. This also exports memblock_is_memory() for all drivers that use pfn_valid() but lack required visibility. After the new config is in place, drop CONFIG_HAVE_ARCH_PFN_VALID from arm64 platforms. Cc: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Will Deacon <will@xxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Mike Rapoport <rppt@xxxxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Cc: linux-mm@xxxxxxxxx Suggested-by: David Hildenbrand <david@xxxxxxxxxx> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx> --- This patch applies on the latest mainline kernel after Mike's series regarding arm64 based pfn_valid(). https://lore.kernel.org/linux-mm/20210422061902.21614-1-rppt@xxxxxxxxxx/T/#t Changes in RFC V2: - Dropped support for arm (32 bit) - Replaced memblock_is_map_memory() check with memblock_is_memory() - MEMBLOCK_NOMAP memory are no longer skipped for pfn_valid() - Updated pfn_to_online_page() per David - Updated free_unused_memmap() to preserve existing semantics per Mike - Exported memblock_is_memory() instead of memblock_is_map_memory() Changes in RFC V1: - https://patchwork.kernel.org/project/linux-mm/patch/1615174073-10520-1-git-send-email-anshuman.khandual@xxxxxxx/ arch/arm64/Kconfig | 2 +- arch/arm64/include/asm/page.h | 1 - arch/arm64/mm/init.c | 41 ----------------------------------- include/linux/mmzone.h | 18 ++++++++++++++- mm/Kconfig | 9 ++++++++ mm/memblock.c | 8 +++++-- mm/memory_hotplug.c | 5 +++++ 7 files changed, 38 insertions(+), 46 deletions(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index b4a9b493ce72..4cdc3570ffa9 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -144,7 +144,6 @@ config ARM64 select HAVE_ARCH_KGDB select HAVE_ARCH_MMAP_RND_BITS select HAVE_ARCH_MMAP_RND_COMPAT_BITS if COMPAT - select HAVE_ARCH_PFN_VALID select HAVE_ARCH_PREL32_RELOCATIONS select HAVE_ARCH_SECCOMP_FILTER select HAVE_ARCH_STACKLEAK @@ -167,6 +166,7 @@ config ARM64 if $(cc-option,-fpatchable-function-entry=2) select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY \ if DYNAMIC_FTRACE_WITH_REGS + select HAVE_EARLY_SECTION_MEMMAP_HOLES select HAVE_EFFICIENT_UNALIGNED_ACCESS select HAVE_FAST_GUP select HAVE_FTRACE_MCOUNT_RECORD diff --git a/arch/arm64/include/asm/page.h b/arch/arm64/include/asm/page.h index 75ddfe671393..fcbef3eec4b2 100644 --- a/arch/arm64/include/asm/page.h +++ b/arch/arm64/include/asm/page.h @@ -37,7 +37,6 @@ void copy_highpage(struct page *to, struct page *from); typedef struct page *pgtable_t; -int pfn_valid(unsigned long pfn); int pfn_is_map_memory(unsigned long pfn); #include <asm/memory.h> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c index f431b38d0837..5731a11550d8 100644 --- a/arch/arm64/mm/init.c +++ b/arch/arm64/mm/init.c @@ -217,47 +217,6 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max) free_area_init(max_zone_pfns); } -int pfn_valid(unsigned long pfn) -{ - phys_addr_t addr = PFN_PHYS(pfn); - - /* - * Ensure the upper PAGE_SHIFT bits are clear in the - * pfn. Else it might lead to false positives when - * some of the upper bits are set, but the lower bits - * match a valid pfn. - */ - if (PHYS_PFN(addr) != pfn) - return 0; - -#ifdef CONFIG_SPARSEMEM -{ - struct mem_section *ms; - - if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS) - return 0; - - ms = __pfn_to_section(pfn); - if (!valid_section(ms)) - return 0; - - /* - * ZONE_DEVICE memory does not have the memblock entries. - * memblock_is_memory() check for ZONE_DEVICE based - * addresses will always fail. Even the normal hotplugged - * memory will never have MEMBLOCK_NOMAP flag set in their - * memblock entries. Skip memblock search for all non early - * memory sections covering all of hotplug memory including - * both normal and ZONE_DEVICE based. - */ - if (!early_section(ms)) - return pfn_section_valid(ms, pfn); -} -#endif - return memblock_is_memory(addr); -} -EXPORT_SYMBOL(pfn_valid); - int pfn_is_map_memory(unsigned long pfn) { phys_addr_t addr = PFN_PHYS(pfn); diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 961f0eeefb62..18bf71665211 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -1421,10 +1421,22 @@ static inline int pfn_section_valid(struct mem_section *ms, unsigned long pfn) * * Return: 1 for PFNs that have memory map entries and 0 otherwise */ +bool memblock_is_memory(phys_addr_t addr); + static inline int pfn_valid(unsigned long pfn) { + phys_addr_t addr = PFN_PHYS(pfn); struct mem_section *ms; + /* + * Ensure the upper PAGE_SHIFT bits are clear in the + * pfn. Else it might lead to false positives when + * some of the upper bits are set, but the lower bits + * match a valid pfn. + */ + if (PHYS_PFN(addr) != pfn) + return 0; + if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS) return 0; ms = __nr_to_section(pfn_to_section_nr(pfn)); @@ -1434,7 +1446,11 @@ static inline int pfn_valid(unsigned long pfn) * Traditionally early sections always returned pfn_valid() for * the entire section-sized span. */ - return early_section(ms) || pfn_section_valid(ms, pfn); + if (early_section(ms)) + return IS_ENABLED(CONFIG_HAVE_EARLY_SECTION_MEMMAP_HOLES) ? + memblock_is_memory(pfn << PAGE_SHIFT) : 1; + + return pfn_section_valid(ms, pfn); } #endif diff --git a/mm/Kconfig b/mm/Kconfig index 24c045b24b95..db7128111874 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -135,6 +135,15 @@ config HAVE_FAST_GUP config ARCH_KEEP_MEMBLOCK bool +config HAVE_EARLY_SECTION_MEMMAP_HOLES + depends on ARCH_KEEP_MEMBLOCK && SPARSEMEM_VMEMMAP + def_bool n + help + Early sections on certain platforms might have some memory ranges that + are not backed with struct page mappings. When subscribed, this option + enables special handling for those memory ranges in certain situations + such as pfn_valid(). + # Keep arch NUMA mapping infrastructure post-init. config NUMA_KEEP_MEMINFO bool diff --git a/mm/memblock.c b/mm/memblock.c index 3abf2c3fea7f..93f8a9c8428d 100644 --- a/mm/memblock.c +++ b/mm/memblock.c @@ -1740,6 +1740,7 @@ bool __init_memblock memblock_is_memory(phys_addr_t addr) { return memblock_search(&memblock.memory, addr) != -1; } +EXPORT_SYMBOL(memblock_is_memory); bool __init_memblock memblock_is_map_memory(phys_addr_t addr) { @@ -1931,8 +1932,11 @@ static void __init free_unused_memmap(void) unsigned long start, end, prev_end = 0; int i; - if (!IS_ENABLED(CONFIG_HAVE_ARCH_PFN_VALID) || - IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP)) + if (IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP)) + return; + + if (!IS_ENABLED(CONFIG_HAVE_EARLY_SECTION_MEMMAP_HOLES) && + !IS_ENABLED(CONFIG_HAVE_ARCH_PFN_VALID)) return; /* diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 0cdbbfbc5757..8c78b6a3d888 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -309,6 +309,11 @@ struct page *pfn_to_online_page(unsigned long pfn) * Save some code text when online_section() + * pfn_section_valid() are sufficient. */ + if (IS_ENABLED(CONFIG_HAVE_EARLY_SECTION_MEMMAP_HOLES)) { + if (early_section(ms) && !memblock_is_memory(PFN_PHYS(pfn))) + return NULL; + } + if (IS_ENABLED(CONFIG_HAVE_ARCH_PFN_VALID) && !pfn_valid(pfn)) return NULL; -- 2.20.1
