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mm/memory_hotplug: add __add_memory_driver_managed() with online_type arg

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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 <gourry@gourry.net>
Acked-by: David Hildenbrand (Arm) <david@kernel.org>
Reviewed-by: Pankaj Gupta <pankaj.gupta@amd.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Dan Williams <djbw@kernel.org>
Cc: Alison Schofield <alison.schofield@intel.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Gregory Price
2026-07-12 11:44:59 -04:00
committed by Andrew Morton
parent 7e00a85f78
commit 2b047c8a8c
2 changed files with 56 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

3
include/linux/memory_hotplug.h
View File

@@ -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);

61
mm/memory_hotplug.c
View File

@@ -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);
/*