On 1/11/21 4:21 PM, David Hildenbrand wrote: > On 17.12.20 16:28, Anshuman Khandual wrote: >> This introduces memhp_range_allowed() which can be called in various memory >> hotplug paths to prevalidate the address range which is being added, with >> the platform. Then memhp_range_allowed() calls memhp_get_pluggable_range() >> which provides applicable address range depending on whether linear mapping >> is required or not. For ranges that require linear mapping, it calls a new >> arch callback arch_get_mappable_range() which the platform can override. So >> the new callback, in turn provides the platform an opportunity to configure >> acceptable memory hotplug address ranges in case there are constraints. >> >> This mechanism will help prevent platform specific errors deep down during >> hotplug calls. This drops now redundant check_hotplug_memory_addressable() >> check in __add_pages() but instead adds a VM_BUG_ON() check which would >> ensure that the range has been validated with memhp_range_allowed() earlier >> in the call chain. Besides memhp_get_pluggable_range() also can be used by >> potential memory hotplug callers to avail the allowed physical range which >> would go through on a given platform. >> >> This does not really add any new range check in generic memory hotplug but >> instead compensates for lost checks in arch_add_memory() where applicable >> and check_hotplug_memory_addressable(), with unified memhp_range_allowed(). >> > > Subject s/mm\/hotplug/mm\/memory_hotplug/ Sure, will do. > > Everywhere in this patch: Use "true/false" for boolean values. Sure, will change. > >> Cc: David Hildenbrand <david@xxxxxxxxxx> >> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> >> Cc: linux-mm@xxxxxxxxx >> Cc: linux-kernel@xxxxxxxxxxxxxxx >> Suggested-by: David Hildenbrand <david@xxxxxxxxxx> >> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx> >> --- >> include/linux/memory_hotplug.h | 10 +++++ >> mm/memory_hotplug.c | 79 +++++++++++++++++++++++++--------- >> mm/memremap.c | 6 +++ >> 3 files changed, 75 insertions(+), 20 deletions(-) >> >> diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h >> index 551093b74596..8d72354758c8 100644 >> --- a/include/linux/memory_hotplug.h >> +++ b/include/linux/memory_hotplug.h >> @@ -70,6 +70,9 @@ typedef int __bitwise mhp_t; >> */ >> #define MEMHP_MERGE_RESOURCE ((__force mhp_t)BIT(0)) >> >> +bool memhp_range_allowed(u64 start, u64 size, bool need_mapping); >> +struct range memhp_get_pluggable_range(bool need_mapping); > > AFAIKs, all memhp_get_pluggable_range() users pass "1". Right. > > What about the "add_pages()-only" path? I had dropped memhp_range_allowed() changes for add_pages() in pagemap_range() because you had mentioned not to add any new checks in the generic code. Will add it back if that is preferred.
