Index: linux-stable/arch/x86/mm/highmem_32.c
===================================================================
--- linux-stable.orig/arch/x86/mm/highmem_32.c
+++ linux-stable/arch/x86/mm/highmem_32.c
@@ -21,6 +21,16 @@ void kunmap(struct page *page)
 }
 EXPORT_SYMBOL(kunmap);
 
+#ifdef CONFIF_PREEMPT_RT_FULL
+void *__kmap_prot(struct page *page, pgprot_t prot)
+{
+	might_sleep();
+	if (!PageHighMem(page))
+		return page_address(page);
+	return kmap_high_prot(page, prot);
+}
+#endif
+
 #ifndef CONFIG_PREEMPT_RT_FULL
 /*
  * kmap_atomic/kunmap_atomic is significantly faster than kmap/kunmap because
Index: linux-stable/localversion-rt
===================================================================
--- linux-stable.orig/localversion-rt
+++ linux-stable/localversion-rt
@@ -1 +1 @@
--rt27
+-rt28