The early fixed addresses must all fit into the static L1 table.
Introduce a build assertion to this end.

Signed-off-by: Elias El Yandouzi <eliasely@amazon.com>

----

     Changes in v2:
         * New patch

diff --git a/xen/arch/x86/include/asm/fixmap.h b/xen/arch/x86/include/asm/fixmap.h
index a7ac365fc6..904bee0480 100644
--- a/xen/arch/x86/include/asm/fixmap.h
+++ b/xen/arch/x86/include/asm/fixmap.h
@@ -77,6 +77,11 @@ enum fixed_addresses {
 #define FIXADDR_SIZE  (__end_of_fixed_addresses << PAGE_SHIFT)
 #define FIXADDR_START (FIXADDR_TOP - FIXADDR_SIZE)
 
+static inline void fixaddr_build_assertion(void)
+{
+    BUILD_BUG_ON(FIX_PMAP_END > L1_PAGETABLE_ENTRIES - 1);
+}
+
 extern void __set_fixmap(
     enum fixed_addresses idx, unsigned long mfn, unsigned long flags);
 
-- 
2.40.1