dax/hmem: Request cxl_acpi and cxl_pci before walking Soft Reserved ranges

Ensure cxl_acpi has published CXL Window resources before HMEM walks Soft
Reserved ranges.

Replace MODULE_SOFTDEP("pre: cxl_acpi") with an explicit, synchronous
request_module("cxl_acpi"). MODULE_SOFTDEP() only guarantees eventual
loading, it does not enforce that the dependency has finished init
before the current module runs. This can cause HMEM to start before
cxl_acpi has populated the resource tree, breaking detection of overlaps
between Soft Reserved and CXL Windows.

Also, request cxl_pci before HMEM walks Soft Reserved ranges. Unlike
cxl_acpi, cxl_pci attach is asynchronous and creates dependent devices
that trigger further module loads. Asynchronous probe flushing
(wait_for_device_probe()) is added later in the series in a deferred
context before HMEM makes ownership decisions for Soft Reserved ranges.

Add an additional explicit Kconfig ordering so that CXL_ACPI and CXL_PCI
must be initialized before DEV_DAX_HMEM. This prevents HMEM from consuming
Soft Reserved ranges before CXL drivers have had a chance to claim them.

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>
Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Tested-by: Tomasz Wolski <tomasz.wolski@fujitsu.com>
Link: https://patch.msgid.link/20260322195343.206900-4-Smita.KoralahalliChannabasappa@amd.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

diff --git a/drivers/dax/Kconfig b/drivers/dax/Kconfig
index d656e4c0eb8463d72f9663655f74b2572e31bc6d..3683bb3f2311bcaa47f0f548a8abc3fdc33c88c9 100644 (file)
--- a/drivers/dax/Kconfig
+++ b/drivers/dax/Kconfig
@@ -48,6 +48,8 @@ config DEV_DAX_CXL
        tristate "CXL DAX: direct access to CXL RAM regions"
        depends on CXL_BUS && CXL_REGION && DEV_DAX
        default CXL_REGION && DEV_DAX
+       depends on CXL_ACPI >= DEV_DAX_HMEM
+       depends on CXL_PCI >= DEV_DAX_HMEM
        help
          CXL RAM regions are either mapped by platform-firmware
          and published in the initial system-memory map as "System RAM", mapped

diff --git a/drivers/dax/hmem/hmem.c b/drivers/dax/hmem/hmem.c
index a3d45032355ca9ba5ca184ae22e031677e63c2ee..85e751675f65fdf2c7c6005534a8072789c4318d 100644 (file)
--- a/drivers/dax/hmem/hmem.c
+++ b/drivers/dax/hmem/hmem.c
@@ -145,6 +145,16 @@ static __init int dax_hmem_init(void)
 {
        int rc;
 
+       /*
+        * Ensure that cxl_acpi and cxl_pci have a chance to kick off
+        * CXL topology discovery at least once before scanning the
+        * iomem resource tree for IORES_DESC_CXL resources.
+        */
+       if (IS_ENABLED(CONFIG_DEV_DAX_CXL)) {
+               request_module("cxl_acpi");
+               request_module("cxl_pci");
+       }
+
        rc = platform_driver_register(&dax_hmem_platform_driver);
        if (rc)
                return rc;
@@ -165,13 +175,6 @@ static __exit void dax_hmem_exit(void)
 module_init(dax_hmem_init);
 module_exit(dax_hmem_exit);
 
-/* Allow for CXL to define its own dax regions */
-#if IS_ENABLED(CONFIG_CXL_REGION)
-#if IS_MODULE(CONFIG_CXL_ACPI)
-MODULE_SOFTDEP("pre: cxl_acpi");
-#endif
-#endif
-
 MODULE_ALIAS("platform:hmem*");
 MODULE_ALIAS("platform:hmem_platform*");
 MODULE_DESCRIPTION("HMEM DAX: direct access to 'specific purpose' memory");