mhp_supports_memmap_on_memory is meant to be used by the caller prior to hot-adding memory in order to figure out whether it can enable MHP_MEMMAP_ON_MEMORY or not.
Enabling MHP_MEMMAP_ON_MEMORY requires: - memmap_on_memory_enabled is set (by mhp_memmap_on_memory kernel boot option) - CONFIG_SPARSEMEM_VMEMMAP - architecture support for altmap - hot-added range spans a single memory block Note that mhp_memmap_on_memory kernel boot option will be added in a coming patch. At the moment, only three architectures support passing altmap when building the page tables: x86, POWERPC and ARM. Define an arch_support_memmap_on_memory function on those architectures that returns true, and define a __weak variant of it that will be used on the others. Signed-off-by: Oscar Salvador <[email protected]> --- arch/arm64/mm/mmu.c | 5 +++++ arch/powerpc/mm/mem.c | 5 +++++ arch/x86/mm/init_64.c | 5 +++++ include/linux/memory_hotplug.h | 10 ++++++++++ mm/memory_hotplug.c | 24 ++++++++++++++++++++++++ 5 files changed, 49 insertions(+) diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 30c6dd02e706..8a33ac97dcbb 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -1454,6 +1454,11 @@ static bool inside_linear_region(u64 start, u64 size) (start + size - 1) <= __pa(PAGE_END - 1); } +bool arch_support_memmap_on_memory(void) +{ + return true; +} + int arch_add_memory(int nid, u64 start, u64 size, struct mhp_params *params) { diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c index 0694bdcce653..c5ef015c3189 100644 --- a/arch/powerpc/mm/mem.c +++ b/arch/powerpc/mm/mem.c @@ -181,6 +181,11 @@ void __ref arch_remove_memory(int nid, u64 start, u64 size, __remove_pages(start_pfn, nr_pages, altmap); arch_remove_linear_mapping(start, size); } + +bool arch_support_memmap_on_memory(void) +{ + return true; +} #endif #ifndef CONFIG_NEED_MULTIPLE_NODES diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index b5a3fa4033d3..ffb9d87c77e8 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -860,6 +860,11 @@ int add_pages(int nid, unsigned long start_pfn, unsigned long nr_pages, return ret; } +bool arch_support_memmap_on_memory(void) +{ + return true; +} + int arch_add_memory(int nid, u64 start, u64 size, struct mhp_params *params) { diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h index 15acce5ab106..a54310abee79 100644 --- a/include/linux/memory_hotplug.h +++ b/include/linux/memory_hotplug.h @@ -70,6 +70,14 @@ typedef int __bitwise mhp_t; */ #define MEMHP_MERGE_RESOURCE ((__force mhp_t)BIT(0)) +/* + * We want memmap (struct page array) to be self contained. + * To do so, we will use the beginning of the hot-added range to build + * the page tables for the memmap array that describes the entire range. + * Only selected architectures support it with SPARSE_VMEMMAP. + */ +#define MHP_MEMMAP_ON_MEMORY ((__force mhp_t)BIT(1)) + /* * Extended parameters for memory hotplug: * altmap: alternative allocator for memmap array (optional) @@ -129,6 +137,7 @@ extern int try_online_node(int nid); extern int arch_add_memory(int nid, u64 start, u64 size, struct mhp_params *params); +extern bool arch_support_memmap_on_memory(void); extern u64 max_mem_size; extern int memhp_online_type_from_str(const char *str); @@ -361,6 +370,7 @@ extern struct page *sparse_decode_mem_map(unsigned long coded_mem_map, unsigned long pnum); extern struct zone *zone_for_pfn_range(int online_type, int nid, unsigned start_pfn, unsigned long nr_pages); +extern bool mhp_supports_memmap_on_memory(unsigned long size); extern int arch_create_linear_mapping(int nid, u64 start, u64 size, struct mhp_params *params); void arch_remove_linear_mapping(u64 start, u64 size); diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index a8cef4955907..e3c310225a60 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1011,6 +1011,20 @@ static int online_memory_block(struct memory_block *mem, void *arg) return device_online(&mem->dev); } +bool __weak arch_support_memmap_on_memory(void) +{ + return false; +} + +bool mhp_supports_memmap_on_memory(unsigned long size) +{ + if (!arch_support_memmap_on_memory() || + !IS_ENABLED(CONFIG_SPARSEMEM_VMEMMAP) || + size > memory_block_size_bytes()) + return false; + return true; +} + /* * NOTE: The caller must call lock_device_hotplug() to serialize hotplug * and online/offline operations (triggered e.g. by sysfs). @@ -1046,6 +1060,16 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) goto error; new_node = ret; + /* + * Return -EINVAL if caller specified MHP_MEMMAP_ON_MEMORY and we do + * not support it. + */ + if ((mhp_flags & MHP_MEMMAP_ON_MEMORY) && + !mhp_supports_memmap_on_memory(size)) { + ret = -EINVAL; + goto error; + } + /* call arch's memory hotadd */ ret = arch_add_memory(nid, start, size, ¶ms); if (ret < 0) -- 2.26.2
