[PATCH v6 4/9] dax/cxl, hmem: Initialize hmem early and defer dax_cxl binding

Smita Koralahalli
2026-02-10T06:45:23Z

From: Dan Williams <dan.j.williams@intel.com>

Move hmem/ earlier in the dax Makefile so that hmem_init() runs before
dax_cxl.

In addition, defer registration of the dax_cxl driver to a workqueue
instead of using module_cxl_driver(). This ensures that dax_hmem has
an opportunity to initialize and register its deferred callback and make
ownership decisions before dax_cxl begins probing and claiming Soft
Reserved ranges.

Mark the dax_cxl driver as PROBE_PREFER_ASYNCHRONOUS so its probe runs
out of line from other synchronous probing avoiding ordering
dependencies while coordinating ownership decisions with dax_hmem.

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com>
---
drivers/dax/Makefile | 3 +--
drivers/dax/cxl.c | 27 ++++++++++++++++++++++++++-
2 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/drivers/dax/Makefile b/drivers/dax/Makefile
index 5ed5c39857c8..70e996bf1526 100644
--- a/drivers/dax/Makefile
+++ b/drivers/dax/Makefile
@@ -1,4 +1,5 @@
# SPDX-License-Identifier: GPL-2.0
+obj-y += hmem/
obj-$(CONFIG_DAX) += dax.o
obj-$(CONFIG_DEV_DAX) += device_dax.o
obj-$(CONFIG_DEV_DAX_KMEM) += kmem.o
@@ -10,5 +11,3 @@ dax-y += bus.o
device_dax-y := device.o
dax_pmem-y := pmem.o
dax_cxl-y := cxl.o
-
-obj-y += hmem/
diff --git a/drivers/dax/cxl.c b/drivers/dax/cxl.c
index 13cd94d32ff7..a2136adfa186 100644
--- a/drivers/dax/cxl.c
+++ b/drivers/dax/cxl.c
@@ -38,10 +38,35 @@ static struct cxl_driver cxl_dax_region_driver = {
.id = CXL_DEVICE_DAX_REGION,
.drv = {
.suppress_bind_attrs = true,
+ .probe_type = PROBE_PREFER_ASYNCHRONOUS,
},
};

-module_cxl_driver(cxl_dax_region_driver);
+static void cxl_dax_region_driver_register(struct work_struct *work)
+{
+ cxl_driver_register(&cxl_dax_region_driver);
+}
+
+static DECLARE_WORK(cxl_dax_region_driver_work, cxl_dax_region_driver_register);
+
+static int __init cxl_dax_region_init(void)
+{
+ /*
+ * Need to resolve a race with dax_hmem wanting to drive regions
+ * instead of CXL
+ */
+ queue_work(system_long_wq, &cxl_dax_region_driver_work);
+ return 0;
+}
+module_init(cxl_dax_region_init);
+
+static void __exit cxl_dax_region_exit(void)
+{
+ flush_work(&cxl_dax_region_driver_work);
+ cxl_driver_unregister(&cxl_dax_region_driver);
+}
+module_exit(cxl_dax_region_exit);
+
MODULE_ALIAS_CXL(CXL_DEVICE_DAX_REGION);
MODULE_DESCRIPTION("CXL DAX: direct access to CXL regions");
MODULE_LICENSE("GPL");
--
2.17.1