+/**
+ * topology_get_logical_id - Retrieve the logical ID at a given topology domain level
+ * @apicid: The APIC ID for which to lookup the logical ID
+ * @at_level: The topology domain level to use
+ *
+ * @apicid must be a full APIC ID, not the normalized variant. It's valid to have
+ * all bits below the domain level specified by @at_level to be clear. So both
+ * real APIC IDs and backshifted normalized APIC IDs work correctly.
+ *
+ * Returns:
+ * - >= 0: The requested logical ID
+ * - -ERANGE: @apicid is out of range
+ * - -ENODEV: @apicid is not registered
+ */
+int topology_get_logical_id(u32 apicid, enum x86_topology_domains at_level)
+{
+ /* Remove the bits below @at_level to get the proper level ID of @apicid */
+ unsigned int lvlid = topo_apicid(apicid, at_level);
+
+ if (lvlid >= MAX_LOCAL_APIC)
+ return -ERANGE;
+ if (!test_bit(lvlid, apic_maps[at_level].map))
+ return -ENODEV;
+ /* Get the number of set bits before @lvlid. */
+ return bitmap_weight(apic_maps[at_level].map, lvlid);
+}
+EXPORT_SYMBOL_GPL(topology_get_logical_id);
+