[PATCH v2 06/13] drivers/base/memory: Add cxl_offline_memory() to offline a physical range
From: Fabio M. De Francesco <hidden>
Date: 2026-08-25 02:27:25
Also in:
driver-core, linux-cxl, linux-mm, linux-pci, lkml
Subsystem:
driver core, kobjects, debugfs and sysfs, memory hot(un)plug, memory management - core, the rest · Maintainers:
Greg Kroah-Hartman, "Rafael J. Wysocki", Danilo Krummrich, David Hildenbrand, Oscar Salvador, Andrew Morton, Linus Torvalds
A CXL region whose capacity is online as System RAM must be taken offline before a Secondary Bus Reset of the CXL Downstream Port it is reached through. Add cxl_offline_memory() to offline the memory blocks spanning a physical range, exported in the CXL_MHP namespace since the CXL core is its only caller. Signed-off-by: Fabio M. De Francesco <redacted> --- drivers/base/memory.c | 36 ++++++++++++++++++++++++++++++++++++ include/linux/memory.h | 5 +++++ 2 files changed, 41 insertions(+)
diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index bcfe2d9f4adb..ce89b251d34a 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c@@ -1018,6 +1018,42 @@ int walk_memory_blocks(unsigned long start, unsigned long size, return ret; } +static int cxl_offline_memory_block(struct memory_block *mem, void *arg) +{ + int rc = device_offline(&mem->dev); + + /* device_offline() returns a positive value when already offline. */ + if (rc > 0) + return 0; + + return rc; +} + +/** + * cxl_offline_memory - offline the memory blocks spanning a physical range + * @start: start of the range, memory-block aligned + * @size: size of the range, a multiple of the memory block size + * + * Offline every memory block in [start, start + size). The blocks are offlined + * but not removed, so the range can be brought back online afterward. The + * caller owns the range and this performs no validation on it. + * + * Return: 0 on success, negative errno if a block cannot be offlined. + * + * Context: process context. Sleeps and takes the memory hotplug lock. + */ +int cxl_offline_memory(u64 start, u64 size) +{ + int rc; + + lock_device_hotplug(); + rc = walk_memory_blocks(start, size, NULL, cxl_offline_memory_block); + unlock_device_hotplug(); + + return rc; +} +EXPORT_SYMBOL_NS_GPL(cxl_offline_memory, "CXL_MHP"); + struct for_each_memory_block_cb_data { walk_memory_blocks_func_t func; void *arg;
diff --git a/include/linux/memory.h b/include/linux/memory.h
index 463dc02f6cff..5dc0b96fb004 100644
--- a/include/linux/memory.h
+++ b/include/linux/memory.h@@ -149,6 +149,10 @@ static inline unsigned long memory_block_advised_max_size(void) { return 0; } +static inline int cxl_offline_memory(u64 start, u64 size) +{ + return 0; +} #else /* CONFIG_MEMORY_HOTPLUG */ extern int register_memory_notifier(struct notifier_block *nb); extern void unregister_memory_notifier(struct notifier_block *nb);
@@ -167,6 +171,7 @@ typedef int (*walk_memory_blocks_func_t)(struct memory_block *, void *); extern int walk_memory_blocks(unsigned long start, unsigned long size, void *arg, walk_memory_blocks_func_t func); extern int for_each_memory_block(void *arg, walk_memory_blocks_func_t func); +int cxl_offline_memory(u64 start, u64 size); extern int memory_group_register_static(int nid, unsigned long max_pages); extern int memory_group_register_dynamic(int nid, unsigned long unit_pages);
--
2.55.0