+#ifdef CONFIG_X86
+ /*
+ * high_memory isn't direct mapped memory so retrieving its physical
+ * address isn't appropriate. But it would be useful to check the
+ * physical address of the highmem boundary so it's justfiable to get
+ * the physical address from it. On x86 there is a validation check for
+ * this case, so the following workaround is needed to avoid it.
+ */
+ highmem_start = __pa_nodebug(high_memory);
+#else
+ highmem_start = __pa(high_memory);
+#endif