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 :) > + > + 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 > 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? > /* > 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 > -- Sincerely yours, Mike.
