[PATCH v7 5/7] cxl/region: Add helper to check Soft Reserved containment by CXL regions

[Smita Koralahalli]

Add a helper to determine whether a given Soft Reserved memory range is
fully contained within the committed CXL region.

This helper provides a primitive for policy decisions in subsequent
patches such as co-ordination with dax_hmem to determine whether CXL has
fully claimed ownership of Soft Reserved memory ranges.

Signed-off-by: Smita Koralahalli <Smita.KoralahalliChannabasappa@xxxxxxx>
Reviewed-by: Jonathan Cameron <jonathan.cameron@xxxxxxxxxx>
Reviewed-by: Dave Jiang <dave.jiang@xxxxxxxxx>
Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
 drivers/cxl/core/region.c | 30 ++++++++++++++++++++++++++++++
 include/cxl/cxl.h         | 15 +++++++++++++++
 2 files changed, 45 insertions(+)
 create mode 100644 include/cxl/cxl.h

diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 42874948b589..f7b20f60ac5c 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -12,6 +12,7 @@
 #include <linux/idr.h>
 #include <linux/memory-tiers.h>
 #include <linux/string_choices.h>
+#include <cxl/cxl.h>
 #include <cxlmem.h>
 #include <cxl.h>
 #include "core.h"
@@ -4173,6 +4174,35 @@ static int cxl_region_setup_poison(struct cxl_region *cxlr)
 	return devm_add_action_or_reset(dev, remove_debugfs, dentry);
 }
 
+static int region_contains_resource(struct device *dev, void *data)
+{
+	struct resource *res = data;
+	struct cxl_region *cxlr;
+	struct cxl_region_params *p;
+
+	if (!is_cxl_region(dev))
+		return 0;
+
+	cxlr = to_cxl_region(dev);
+	p = &cxlr->params;
+
+	if (p->state != CXL_CONFIG_COMMIT)
+		return 0;
+
+	if (!p->res)
+		return 0;
+
+	return resource_contains(p->res, res) ? 1 : 0;
+}
+
+bool cxl_region_contains_resource(struct resource *res)
+{
+	guard(rwsem_read)(&cxl_rwsem.region);
+	return bus_for_each_dev(&cxl_bus_type, NULL, res,
+				region_contains_resource) != 0;
+}
+EXPORT_SYMBOL_GPL(cxl_region_contains_resource);
+
 static int cxl_region_can_probe(struct cxl_region *cxlr)
 {
 	struct cxl_region_params *p = &cxlr->params;
diff --git a/include/cxl/cxl.h b/include/cxl/cxl.h
new file mode 100644
index 000000000000..b12d3d0f6658
--- /dev/null
+++ b/include/cxl/cxl.h
@@ -0,0 +1,15 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* Copyright (c) 2026 Advanced Micro Devices, Inc. */
+#ifndef _CXL_H_
+#define _CXL_H_
+
+#ifdef CONFIG_CXL_REGION
+bool cxl_region_contains_resource(struct resource *res);
+#else
+static inline bool cxl_region_contains_resource(struct resource *res)
+{
+	return false;
+}
+#endif
+
+#endif /* _CXL_H_ */
-- 
2.17.1