diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
index 1cc9be85ba4c..529baa8a1759 100644
--- a/drivers/cxl/core/hdm.c
+++ b/drivers/cxl/core/hdm.c
@@ -839,6 +839,8 @@ static int init_hdm_decoder(struct cxl_port *port, struct cxl_decoder *cxld,
 			cxld->target_type = CXL_DECODER_HOSTONLYMEM;
 		else
 			cxld->target_type = CXL_DECODER_DEVMEM;
+
+		guard(rwsem_write)(&cxl_region_rwsem);
 		if (cxld->id != cxl_num_decoders_committed(port)) {
 			dev_warn(&port->dev,
 				 "decoder%d.%d: Committed out of order\n",