On 6/30/26 2:18 PM, Gregory Price wrote: > 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. > > Acked-by: David Hildenbrand (Arm) <[email protected]> > Reviewed-by: Pankaj Gupta <[email protected]> > Signed-off-by: Gregory Price <[email protected]> Reviewed-by: Dave Jiang <[email protected]> > --- > 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 4d51fcb93a37..ff3b865ea7e7 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 494257054095..a66346def504 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1494,10 +1494,10 @@ 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; > @@ -1585,7 +1585,7 @@ 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); > > @@ -1603,7 +1603,13 @@ 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; > @@ -1631,7 +1637,15 @@ 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 ($DRIVER)" > + * @mhp_flags: Memory hotplug flags > + * @online_type: Auto-Online behavior (offline, online, kernel, movable) > + * > * Add special, driver-managed memory to the system as system RAM. Such > * memory is not exposed via the raw firmware-provided memmap as system > * RAM, instead, it is detected and added by a driver - during cold boot, > @@ -1639,6 +1653,7 @@ EXPORT_SYMBOL_GPL(add_memory); > * > * Reasons why this memory should not be used for the initial memmap of a > * kexec kernel or for placing kexec images: > + * > * - The booting kernel is in charge of determining how this memory will be > * used (e.g., use persistent memory as system RAM) > * - Coordination with a hypervisor is required before this memory > @@ -1651,9 +1666,12 @@ EXPORT_SYMBOL_GPL(add_memory); > * > * The resource_name (visible via /proc/iomem) has to have the format > * "System RAM ($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; > @@ -1663,6 +1681,9 @@ 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); > @@ -1671,7 +1692,7 @@ 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); > > @@ -1679,6 +1700,30 @@ 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); > > /*
