On 4/22/21 1:57 PM, Mike Rapoport wrote: > On Thu, Apr 22, 2021 at 01:20:23PM +0530, Anshuman Khandual wrote: >> 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; > > Nit: we already did > > addr = PFN_PHYS(pfn); > > a few lines above :) Yeah, will use the addr directly here. > >> + >> + 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); > > Please make it inside #ifdef CONFIG_ARCH_MEMBLOCK CONFIG_ARCH_KEEP_MEMBLOCK ? Wrap it around the EXPORT_SYMBOL() or the entire function 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; > > Can you please add a comment that says that architecture should provide a > way to detect holes in the memory map to be able to free its part? I did not get that completely. If CONFIG_HAVE_EARLY_SECTION_MEMMAP_HOLES is not subscribed, then the platform must provide a method that identifies these memmap holes and process them accordingly in pfn_valid() just to avoid null pointer dereference ? Also the comment should be placed after the second return statement, when its going to free unused memmap segments.
