From 2b047c8a8c2769319a6ed17c47773c285b047080 Mon Sep 17 00:00:00 2001 From: Gregory Price Date: Sun, 12 Jul 2026 11:44:59 -0400 Subject: [PATCH] mm/memory_hotplug: add __add_memory_driver_managed() with online_type arg Existing callers of add_memory_driver_managed cannot select the preferred online type (ZONE_NORMAL vs ZONE_MOVABLE), requiring it to hot-add memory as offline blocks, and then follow up by onlining each memory block individually. Most drivers prefer the system default, but the CXL driver wants to plumb a preferred policy through the dax kmem driver. Refactor APIs to add a new interface which allows the dax kmem module to select a preferred policy. Overriding the configured auto-online policy is only safe for known in-tree modules, where we know the override reflects a different, user-requested policy. We do not want arbitrary out-of-tree drivers silently overriding the system-wide onlining policy, so restrict the new interface to the kmem module using EXPORT_SYMBOL_FOR_MODULES() rather than a plain EXPORT_SYMBOL_GPL(). Other in-tree modules (e.g. cxl_core) can be added to the allowed list as the need arises. Refactor add_memory_driver_managed, extract __add_memory_driver_managed - Add proper kernel-doc for add_memory_driver_managed while refactoring - New helper accepts an explicit online_type. - New helper validates online_type is between OFFLINE and ONLINE_MOVABLE Refactor: add_memory_resource, extract __add_memory_resource - new helper accepts an explicit online_type Original APIs now explicitly pass the system-default to new helpers. No functional change for existing users. Link: https://lore.kernel.org/20260712154505.3564379-6-gourry@gourry.net Signed-off-by: Gregory Price Acked-by: David Hildenbrand (Arm) Reviewed-by: Pankaj Gupta Reviewed-by: Dave Jiang Reviewed-by: Dan Williams Cc: Alison Schofield Cc: Danilo Krummrich Cc: Greg Kroah-Hartman Cc: Hannes Reinecke Cc: Liam R. Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Oscar Salvador Cc: "Rafael J. Wysocki" Cc: Shuah Khan Cc: Suren Baghdasaryan Cc: Vishal Verma Cc: Vlastimil Babka Signed-off-by: Andrew Morton --- include/linux/memory_hotplug.h | 3 ++ mm/memory_hotplug.c | 61 +++++++++++++++++++++++++++++----- 2 files changed, 56 insertions(+), 8 deletions(-) diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h index 5240aa28bc90..d69b273ed304 100644 --- a/include/linux/memory_hotplug.h +++ b/include/linux/memory_hotplug.h @@ -295,6 +295,9 @@ extern int __add_memory(int nid, u64 start, u64 size, mhp_t mhp_flags); extern int add_memory(int nid, u64 start, u64 size, mhp_t mhp_flags); extern int add_memory_resource(int nid, struct resource *resource, mhp_t mhp_flags); +int __add_memory_driver_managed(int nid, u64 start, u64 size, + const char *resource_name, mhp_t mhp_flags, + enum mmop online_type); extern int add_memory_driver_managed(int nid, u64 start, u64 size, const char *resource_name, mhp_t mhp_flags); diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c index 73c4a1b9895d..fe6b38ef9aac 100644 --- a/mm/memory_hotplug.c +++ b/mm/memory_hotplug.c @@ -1497,10 +1497,10 @@ static int create_altmaps_and_memory_blocks(int nid, struct memory_group *group, * * we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */ -int add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) +static int __add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags, + enum mmop online_type) { struct mhp_params params = { .pgprot = pgprot_mhp(PAGE_KERNEL) }; - enum mmop online_type = mhp_get_default_online_type(); enum memblock_flags memblock_flags = MEMBLOCK_NONE; struct memory_group *group = NULL; u64 start, size; @@ -1588,7 +1588,7 @@ int add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) merge_system_ram_resource(res); /* online pages if requested */ - if (mhp_get_default_online_type() != MMOP_OFFLINE) + if (online_type != MMOP_OFFLINE) walk_memory_blocks(start, size, &online_type, online_memory_block); @@ -1606,7 +1606,13 @@ int add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) return ret; } -/* requires device_hotplug_lock, see add_memory_resource() */ +int add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags) +{ + return __add_memory_resource(nid, res, mhp_flags, + mhp_get_default_online_type()); +} + +/* requires device_hotplug_lock, see __add_memory_resource() */ int __add_memory(int nid, u64 start, u64 size, mhp_t mhp_flags) { struct resource *res; @@ -1634,7 +1640,15 @@ int add_memory(int nid, u64 start, u64 size, mhp_t mhp_flags) } EXPORT_SYMBOL_GPL(add_memory); -/* +/** + * __add_memory_driver_managed - add driver-managed memory with explicit online_type + * @nid: NUMA node ID where the memory will be added + * @start: Start physical address of the memory range + * @size: Size of the memory range in bytes + * @resource_name: Resource name in format "System RAM ($DRIVER)" + * @mhp_flags: Memory hotplug flags + * @online_type: Auto-Online behavior (offline, online, kernel, movable) + * * Add special, driver-managed memory to the system as system RAM. Such * memory is not exposed via the raw firmware-provided memmap as system * RAM, instead, it is detected and added by a driver - during cold boot, @@ -1642,6 +1656,7 @@ EXPORT_SYMBOL_GPL(add_memory); * * Reasons why this memory should not be used for the initial memmap of a * kexec kernel or for placing kexec images: + * * - The booting kernel is in charge of determining how this memory will be * used (e.g., use persistent memory as system RAM) * - Coordination with a hypervisor is required before this memory @@ -1654,9 +1669,12 @@ EXPORT_SYMBOL_GPL(add_memory); * * The resource_name (visible via /proc/iomem) has to have the format * "System RAM ($DRIVER)". + * + * Return: 0 on success, negative error code on failure. */ -int add_memory_driver_managed(int nid, u64 start, u64 size, - const char *resource_name, mhp_t mhp_flags) +int __add_memory_driver_managed(int nid, u64 start, u64 size, + const char *resource_name, mhp_t mhp_flags, + enum mmop online_type) { struct resource *res; int rc; @@ -1666,6 +1684,9 @@ int add_memory_driver_managed(int nid, u64 start, u64 size, resource_name[strlen(resource_name) - 1] != ')') return -EINVAL; + if (online_type < MMOP_OFFLINE || online_type > MMOP_ONLINE_MOVABLE) + return -EINVAL; + lock_device_hotplug(); res = register_memory_resource(start, size, resource_name); @@ -1674,7 +1695,7 @@ int add_memory_driver_managed(int nid, u64 start, u64 size, goto out_unlock; } - rc = add_memory_resource(nid, res, mhp_flags); + rc = __add_memory_resource(nid, res, mhp_flags, online_type); if (rc < 0) release_memory_resource(res); @@ -1682,6 +1703,30 @@ int add_memory_driver_managed(int nid, u64 start, u64 size, unlock_device_hotplug(); return rc; } +EXPORT_SYMBOL_FOR_MODULES(__add_memory_driver_managed, "kmem"); + +/** + * add_memory_driver_managed - add driver-managed memory + * @nid: NUMA node ID where the memory will be added + * @start: Start physical address of the memory range + * @size: Size of the memory range in bytes + * @resource_name: Resource name in format "System RAM ($DRIVER)" + * @mhp_flags: Memory hotplug flags + * + * Add driver-managed memory with the system default online type set by + * build config or kernel boot parameter. + * + * See __add_memory_driver_managed for more details. + * + * Return: 0 on success, negative error code on failure. + */ +int add_memory_driver_managed(int nid, u64 start, u64 size, + const char *resource_name, mhp_t mhp_flags) +{ + return __add_memory_driver_managed(nid, start, size, resource_name, + mhp_flags, + mhp_get_default_online_type()); +} EXPORT_SYMBOL_GPL(add_memory_driver_managed); /*