From: Sasha Levin <sashal@kernel.org>
To: stable@vger.kernel.org
Cc: Dan Williams <dan.j.williams@intel.com>,
	Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com>,
	Dave Jiang <dave.jiang@intel.com>,
	Jonathan Cameron <jonathan.cameron@huawei.com>,
	Tomasz Wolski <tomasz.wolski@fujitsu.com>,
	Sasha Levin <sashal@kernel.org>
Subject: [PATCH 6.18.y 1/3] dax/cxl, hmem: Initialize hmem early and defer dax_cxl binding
Date: Tue,  8 Sep 2026 12:01:35 -0400
Message-ID: <20260908160137.2549229-1-sashal@kernel.org>
In-Reply-To: <2026090359-scale-swell-330d@gregkh>
References: <2026090359-scale-swell-330d@gregkh>
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MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

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

[ Upstream commit 39aa1d4be12bf9f685adaa06aa2d997c1c611b16 ]

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: Smita Koralahalli <Smita.KoralahalliChannabasappa@amd.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Tested-by: Tomasz Wolski <tomasz.wolski@fujitsu.com>
Link: https://patch.msgid.link/20260322195343.206900-6-Smita.KoralahalliChannabasappa@amd.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Stable-dep-of: 775d0f4558f4 ("cxl/mce: Make the MCE notifier per-region")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 5ed5c39857c8b..70e996bf15261 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 13cd94d32ff7a..a2136adfa186e 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");
-- 
2.53.0