From c5f1e2d1890935a734c302b9b8579748222b8e1e Mon Sep 17 00:00:00 2001 From: Sumanth Korikkar Date: Mon, 8 Jan 2024 14:27:43 +0100 Subject: mm/memory_hotplug: introduce MEM_PREPARE_ONLINE/MEM_FINISH_OFFLINE notifiers Patch series "implement "memmap on memory" feature on s390". This series provides "memmap on memory" support on s390 platform. "memmap on memory" allows struct pages array to be allocated from the hotplugged memory range instead of allocating it from main system memory. s390 currently preallocates struct pages array for all potentially possible memory, which ensures memory onlining always succeeds, but with the cost of significant memory consumption from the available system memory during boottime. In certain extreme configuration, this could lead to ipl failure. "memmap on memory" ensures struct pages array are populated from self contained hotplugged memory range instead of depleting the available system memory and this could eliminate ipl failure on s390 platform. On other platforms, system might go OOM when the physically hotplugged memory depletes the available memory before it is onlined. Hence, "memmap on memory" feature was introduced as described in commit a08a2ae34613 ("mm,memory_hotplug: allocate memmap from the added memory range"). Unlike other architectures, s390 memory blocks are not physically accessible until it is online. To make it physically accessible two new memory notifiers MEM_PREPARE_ONLINE / MEM_FINISH_OFFLINE are added and this notifier lets the hypervisor inform that the memory should be made physically accessible. This allows for "memmap on memory" initialization during memory hotplug onlining phase, which is performed before calling MEM_GOING_ONLINE notifier. Patch 1 introduces MEM_PREPARE_ONLINE/MEM_FINISH_OFFLINE memory notifiers to prepare the transition of memory to and from a physically accessible state. New mhp_flag MHP_OFFLINE_INACCESSIBLE is introduced to ensure altmap cannot be written when adding memory - before it is set online. This enhancement is crucial for implementing the "memmap on memory" feature for s390 in a subsequent patch. Patches 2 allocates vmemmap pages from self-contained memory range for s390. It allocates memory map (struct pages array) from the hotplugged memory range, rather than using system memory by passing altmap to vmemmap functions. Patch 3 removes unhandled memory notifier types on s390. Patch 4 implements MEM_PREPARE_ONLINE/MEM_FINISH_OFFLINE memory notifiers on s390. MEM_PREPARE_ONLINE memory notifier makes memory block physical accessible via sclp assign command. The notifier ensures self-contained memory maps are accessible and hence enabling the "memmap on memory" on s390. MEM_FINISH_OFFLINE memory notifier shifts the memory block to an inaccessible state via sclp unassign command. Patch 5 finally enables MHP_MEMMAP_ON_MEMORY on s390. This patch (of 5): Introduce MEM_PREPARE_ONLINE/MEM_FINISH_OFFLINE memory notifiers to prepare the transition of memory to and from a physically accessible state. This enhancement is crucial for implementing the "memmap on memory" feature for s390 in a subsequent patch. Platforms such as x86 can support physical memory hotplug via ACPI. When there is physical memory hotplug, ACPI event leads to the memory addition with the following callchain: acpi_memory_device_add() -> acpi_memory_enable_device() -> __add_memory() After this, the hotplugged memory is physically accessible, and altmap support prepared, before the "memmap on memory" initialization in memory_block_online() is called. On s390, memory hotplug works in a different way. The available hotplug memory has to be defined upfront in the hypervisor, but it is made physically accessible only when the user sets it online via sysfs, currently in the MEM_GOING_ONLINE notifier. This is too late and "memmap on memory" initialization is performed before calling MEM_GOING_ONLINE notifier. During the memory hotplug addition phase, altmap support is prepared and during the memory onlining phase s390 requires memory to be physically accessible and then subsequently initiate the "memmap on memory" initialization process. The memory provider will handle new MEM_PREPARE_ONLINE / MEM_FINISH_OFFLINE notifications and make the memory accessible. The mhp_flag MHP_OFFLINE_INACCESSIBLE is introduced and is relevant when used along with MHP_MEMMAP_ON_MEMORY, because the altmap cannot be written (e.g., poisoned) when adding memory -- before it is set online. This allows for adding memory with an altmap that is not currently made available by a hypervisor. When onlining that memory, the hypervisor can be instructed to make that memory accessible via the new notifiers and the onlining phase will not require any memory allocations, which is helpful in low-memory situations. All architectures ignore unknown memory notifiers. Therefore, the introduction of these new notifiers does not result in any functional modifications across architectures. Link: https://lkml.kernel.org/r/20240108132747.3238763-1-sumanthk@linux.ibm.com Link: https://lkml.kernel.org/r/20240108132747.3238763-2-sumanthk@linux.ibm.com Signed-off-by: Sumanth Korikkar Suggested-by: Gerald Schaefer Suggested-by: David Hildenbrand Acked-by: David Hildenbrand Cc: Alexander Gordeev Cc: Aneesh Kumar K.V Cc: Anshuman Khandual Cc: Heiko Carstens Cc: Michal Hocko Cc: Oscar Salvador Cc: Vasily Gorbik Signed-off-by: Andrew Morton --- include/linux/memory.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'include/linux/memory.h') diff --git a/include/linux/memory.h b/include/linux/memory.h index f53cfdaaaa41..939a16bd5cea 100644 --- a/include/linux/memory.h +++ b/include/linux/memory.h @@ -96,8 +96,17 @@ int set_memory_block_size_order(unsigned int order); #define MEM_GOING_ONLINE (1<<3) #define MEM_CANCEL_ONLINE (1<<4) #define MEM_CANCEL_OFFLINE (1<<5) +#define MEM_PREPARE_ONLINE (1<<6) +#define MEM_FINISH_OFFLINE (1<<7) struct memory_notify { + /* + * The altmap_start_pfn and altmap_nr_pages fields are designated for + * specifying the altmap range and are exclusively intended for use in + * MEM_PREPARE_ONLINE/MEM_FINISH_OFFLINE notifiers. + */ + unsigned long altmap_start_pfn; + unsigned long altmap_nr_pages; unsigned long start_pfn; unsigned long nr_pages; int status_change_nid_normal; -- cgit v1.2.3 From 067353a46d8ccdac279ebab97c038c3658e97541 Mon Sep 17 00:00:00 2001 From: Dave Jiang Date: Fri, 8 Mar 2024 14:59:30 -0700 Subject: cxl/region: Add memory hotplug notifier for cxl region When the CXL region is formed, the driver computes the performance data for the region. However this data is not available at the node data collection that has been populated by the HMAT during kernel initialization. Add a memory hotplug notifier to update the access coordinates to the 'struct memory_target' context kept by the HMAT_REPORTING code. Add CXL_CALLBACK_PRI for a memory hotplug callback priority. Set the priority number to be called before HMAT_CALLBACK_PRI. The CXL update must happen before hmat_callback(). A new HMAT_REPORTING helper hmat_update_target_coordinates() is added in order to allow CXL to update the memory_target access coordinates. A new ext_updated member is added to the memory_target to indicate that the access coordinates within the memory_target has been updated by an external agent such as CXL. This prevents data being overwritten by the hmat_update_target_attrs() triggered by hmat_callback(). Cc: Andrew Morton Cc: Rafael J. Wysocki Reviewed-by: Huang, Ying Reviewed-by: Jonathan Cameron Tested-by: Jonathan Cameron Signed-off-by: Dave Jiang Link: https://lore.kernel.org/r/20240308220055.2172956-12-dave.jiang@intel.com Signed-off-by: Dan Williams --- include/linux/memory.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/memory.h') diff --git a/include/linux/memory.h b/include/linux/memory.h index f53cfdaaaa41..d8588256578a 100644 --- a/include/linux/memory.h +++ b/include/linux/memory.h @@ -114,6 +114,7 @@ struct mem_section; #define DEFAULT_CALLBACK_PRI 0 #define SLAB_CALLBACK_PRI 1 #define HMAT_CALLBACK_PRI 2 +#define CXL_CALLBACK_PRI 5 #define MM_COMPUTE_BATCH_PRI 10 #define CPUSET_CALLBACK_PRI 10 #define MEMTIER_HOTPLUG_PRI 100 -- cgit v1.2.3