[PATCH 2/2] cxl/region: skip default driver attach for memdev with attach callbacks

[Gregory Price]

When a CXL memdev has a custom attach callback, cxl_add_to_region()
should not call device_attach() on the auto-discovered region.

The default device_attach() binds the dax driver, which may online
memory via dax_kmem.  The custom attach callback then has to tear down
the dax stack to convert the region to sysram, but dax_kmem refuses to
offline memory during its remove path, leaving regions stuck online.

Skip device_attach() when cxlmd->attach is set.  The attach callback
is responsible for setting up the region after auto-discovery completes
(e.g. adding it as sysram directly).

Signed-off-by: Gregory Price <gourry@xxxxxxxxxx>
---
 drivers/cxl/core/region.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 276046d49f88..e5edeabd9262 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -3971,6 +3971,12 @@ int cxl_add_to_region(struct cxl_endpoint_decoder *cxled)
 	}
 
 	if (attach) {
+		struct cxl_memdev *cxlmd = cxled_to_memdev(cxled);
+
+		/* Skip device_attach if memdev has is own attach callback */
+		if (cxlmd->attach)
+			return 0;
+
 		/*
 		 * If device_attach() fails the range may still be active via
 		 * the platform-firmware memory map, otherwise the driver for
-- 
2.47.3