drivers/base/node: Add a helper function node_update_perf_attrs()

Add helper function node_update_perf_attrs() to allow update of node access
coordinates computed by an external agent such as CXL. The helper allows
updating of coordinates after the attribute being created by HMAT.

Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Link: https://patch.msgid.link/20250829222907.1290912-3-dave.jiang@intel.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>

Author: davejiang

drivers/base/node.c

@@ -248,6 +248,44 @@ void node_set_perf_attrs(unsigned int nid, struct access_coordinate *coord,
 }
 EXPORT_SYMBOL_GPL(node_set_perf_attrs);
 
+/**
+ * node_update_perf_attrs - Update the performance values for given access class
+ * @nid: Node identifier to be updated
+ * @coord: Heterogeneous memory performance coordinates
+ * @access: The access class for the given attributes
+ */
+void node_update_perf_attrs(unsigned int nid, struct access_coordinate *coord,
+			    enum access_coordinate_class access)
+{
+	struct node_access_nodes *access_node;
+	struct node *node;
+	int i;
+
+	if (WARN_ON_ONCE(!node_online(nid)))
+		return;
+
+	node = node_devices[nid];
+	list_for_each_entry(access_node, &node->access_list, list_node) {
+		if (access_node->access != access)
+			continue;
+
+		access_node->coord = *coord;
+		for (i = 0; access_attrs[i]; i++) {
+			sysfs_notify(&access_node->dev.kobj,
+				     NULL, access_attrs[i]->name);
+		}
+		break;
+	}
+
+	/* When setting CPU access coordinates, update mempolicy */
+	if (access != ACCESS_COORDINATE_CPU)
+		return;
+
+	if (mempolicy_set_node_perf(nid, coord))
+		pr_info("failed to set mempolicy attrs for node %d\n", nid);
+}
+EXPORT_SYMBOL_GPL(node_update_perf_attrs);
+
 /**
  * struct node_cache_info - Internal tracking for memory node caches
  * @dev:	Device represeting the cache level

include/linux/node.h

@@ -85,6 +85,8 @@ struct node_cache_attrs {
 void node_add_cache(unsigned int nid, struct node_cache_attrs *cache_attrs);
 void node_set_perf_attrs(unsigned int nid, struct access_coordinate *coord,
 			 enum access_coordinate_class access);
+void node_update_perf_attrs(unsigned int nid, struct access_coordinate *coord,
+			    enum access_coordinate_class access);
 #else
 static inline void node_add_cache(unsigned int nid,
 				  struct node_cache_attrs *cache_attrs)
@@ -96,6 +98,12 @@ static inline void node_set_perf_attrs(unsigned int nid,
 				       enum access_coordinate_class access)
 {
 }
+
+static inline void node_update_perf_attrs(unsigned int nid,
+					  struct access_coordinate *coord,
+					  enum access_coordinate_class access)
+{
+}
 #endif
 
 struct node {