diff --git a/tools/testing/cxl/test/cxl.c b/tools/testing/cxl/test/cxl.c
index ef92dd35e030..057724f27c6b 100644
--- a/tools/testing/cxl/test/cxl.c
+++ b/tools/testing/cxl/test/cxl.c
@@ -1827,11 +1827,29 @@ static struct attribute *cxl_acpi_attrs[] = {
 };
 ATTRIBUTE_GROUPS(cxl_acpi);
 
+static bool __init have_multiple_modparms(void)
+{
+	int count = 0;
+
+	if (interleave_arithmetic)
+		count++;
+	if (extended_linear_cache)
+		count++;
+	if (hmem_test)
+		count++;
+
+	return count > 1;
+}
+
 static __init int cxl_test_init(void)
 {
 	int rc, i;
 	struct range mappable;
 
+	/* Enforce a single module param active at a time */
+	if (have_multiple_modparms())
+		return -EINVAL;
+
 	if (!IS_ALIGNED(mock_auto_region_size, PMD_SIZE)) {
 		pr_err_once("mock_auto_region_size %d must be PMD-aligned\n",
 			    mock_auto_region_size);
diff --git a/tools/testing/cxl/test/hmem_test.c b/tools/testing/cxl/test/hmem_test.c
index 3a1a089e1721..0fa00f7e16db 100644
--- a/tools/testing/cxl/test/hmem_test.c
+++ b/tools/testing/cxl/test/hmem_test.c
@@ -3,8 +3,9 @@
 #include <linux/moduleparam.h>
 #include <linux/workqueue.h>
 #include "../../../drivers/dax/bus.h"
+#include "mock.h"
 
-static bool hmem_test;
+bool hmem_test;
 
 static void hmem_test_work(struct work_struct *work)
 {
diff --git a/tools/testing/cxl/test/mock.h b/tools/testing/cxl/test/mock.h
index 4f57dc80ae7d..846d7c5d6eaa 100644
--- a/tools/testing/cxl/test/mock.h
+++ b/tools/testing/cxl/test/mock.h
@@ -5,6 +5,8 @@
 #include <linux/dax.h>
 #include <cxl.h>
 
+extern bool hmem_test;
+
 struct cxl_mock_ops {
 	struct list_head list;
 	bool (*is_mock_adev)(struct acpi_device *dev);