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Message-ID: <20260114235022.3437787-3-gourry@gourry.net>
Date: Wed, 14 Jan 2026 18:50:18 -0500
From: Gregory Price <gourry@...rry.net>
To: linux-mm@...ck.org
Cc: linux-cxl@...r.kernel.org,
nvdimm@...ts.linux.dev,
linux-kernel@...r.kernel.org,
virtualization@...ts.linux.dev,
kernel-team@...a.com,
dan.j.williams@...el.com,
vishal.l.verma@...el.com,
dave.jiang@...el.com,
david@...nel.org,
mst@...hat.com,
jasowang@...hat.com,
xuanzhuo@...ux.alibaba.com,
eperezma@...hat.com,
osalvador@...e.de,
akpm@...ux-foundation.org
Subject: [PATCH v2 2/5] mm/memory_hotplug: add 'online_type' argument to add_memory_driver_managed
Enable external callers to select how to online the memory rather than
implicitly depending on the system defauilt.
Refactor: Extract __add_memory_resource to take an explicit online type,
and update add_memory_resource to pass the system default.
Export mhp_get_default_online_type() and update existing callers of
add_memory_driver_managed to use it explicitly to make it clear what the
behavior of the function is.
dax_kmem and virtio_mem drivers were updated.
Signed-off-by: Gregory Price <gourry@...rry.net>
---
drivers/dax/kmem.c | 3 ++-
drivers/virtio/virtio_mem.c | 3 ++-
include/linux/memory_hotplug.h | 2 +-
mm/memory_hotplug.c | 31 +++++++++++++++++++++++--------
4 files changed, 28 insertions(+), 11 deletions(-)
diff --git a/drivers/dax/kmem.c b/drivers/dax/kmem.c
index c036e4d0b610..bb13d9ced2e9 100644
--- a/drivers/dax/kmem.c
+++ b/drivers/dax/kmem.c
@@ -175,7 +175,8 @@ static int dev_dax_kmem_probe(struct dev_dax *dev_dax)
* this as RAM automatically.
*/
rc = add_memory_driver_managed(data->mgid, range.start,
- range_len(&range), kmem_name, mhp_flags);
+ range_len(&range), kmem_name, mhp_flags,
+ mhp_get_default_online_type());
if (rc) {
dev_warn(dev, "mapping%d: %#llx-%#llx memory add failed\n",
diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index 1688ecd69a04..63c0b2b235ab 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -654,7 +654,8 @@ static int virtio_mem_add_memory(struct virtio_mem *vm, uint64_t addr,
/* Memory might get onlined immediately. */
atomic64_add(size, &vm->offline_size);
rc = add_memory_driver_managed(vm->mgid, addr, size, vm->resource_name,
- MHP_MERGE_RESOURCE | MHP_NID_IS_MGID);
+ MHP_MERGE_RESOURCE | MHP_NID_IS_MGID,
+ mhp_get_default_online_type());
if (rc) {
atomic64_sub(size, &vm->offline_size);
dev_warn(&vm->vdev->dev, "adding memory failed: %d\n", rc);
diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index f2f16cdd73ee..b68bc410db67 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -295,7 +295,7 @@ extern int add_memory_resource(int nid, struct resource *resource,
mhp_t mhp_flags);
extern int add_memory_driver_managed(int nid, u64 start, u64 size,
const char *resource_name,
- mhp_t mhp_flags);
+ mhp_t mhp_flags, int online_type);
extern void move_pfn_range_to_zone(struct zone *zone, unsigned long start_pfn,
unsigned long nr_pages,
struct vmem_altmap *altmap, int migratetype,
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 5718556121f0..2b4e31161fc1 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -239,6 +239,7 @@ int mhp_get_default_online_type(void)
return mhp_default_online_type;
}
+EXPORT_SYMBOL_GPL(mhp_get_default_online_type);
void mhp_set_default_online_type(int online_type)
{
@@ -1490,7 +1491,8 @@ 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,
+ int online_type)
{
struct mhp_params params = { .pgprot = pgprot_mhp(PAGE_KERNEL) };
enum memblock_flags memblock_flags = MEMBLOCK_NONE;
@@ -1580,12 +1582,9 @@ 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) {
- int online_type = mhp_get_default_online_type();
-
+ if (online_type != MMOP_OFFLINE)
walk_memory_blocks(start, size, &online_type,
online_memory_block);
- }
return ret;
error:
@@ -1601,7 +1600,13 @@ 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;
@@ -1649,9 +1654,16 @@ EXPORT_SYMBOL_GPL(add_memory);
*
* The resource_name (visible via /proc/iomem) has to have the format
* "System RAM ($DRIVER)".
+ *
+ * @online_type specifies the online behavior: MMOP_ONLINE, MMOP_ONLINE_KERNEL,
+ * MMOP_ONLINE_MOVABLE to online with that type, MMOP_OFFLINE to leave offline.
+ * Users that want the system default should call mhp_get_default_online_type().
+ *
+ * Returns 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)
+ const char *resource_name, mhp_t mhp_flags,
+ int online_type)
{
struct resource *res;
int rc;
@@ -1661,6 +1673,9 @@ int add_memory_driver_managed(int nid, u64 start, u64 size,
resource_name[strlen(resource_name) - 1] != ')')
return -EINVAL;
+ if (online_type < 0 || online_type > MMOP_ONLINE_MOVABLE)
+ return -EINVAL;
+
lock_device_hotplug();
res = register_memory_resource(start, size, resource_name);
@@ -1669,7 +1684,7 @@ 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);
--
2.52.0
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