diff --git a/xen/arch/x86/boot/head.S b/xen/arch/x86/boot/head.S
index 250587fdf0..d152af4542 100644
--- a/xen/arch/x86/boot/head.S
+++ b/xen/arch/x86/boot/head.S
@@ -661,15 +661,9 @@ trampoline_setup:
         mov     %eax,sym_fs(boot_tsc_stamp)
         mov     %edx,sym_fs(boot_tsc_stamp)+4
 
-        /*
-         * Update frame addresses in page tables excluding l2_identmap
-         * without its first entry which points to l1_identmap.
-         */
+        /* Relocate pagetables to point at Xen's current location in memory. */
         mov     $((__page_tables_end-__page_tables_start)/8),%ecx
-        mov     $(((l2_identmap-__page_tables_start)/8)+1),%edx
-1:      cmp     $((l2_identmap+l2_identmap_sizeof-__page_tables_start)/8),%ecx
-        cmove   %edx,%ecx
-        testl   $_PAGE_PRESENT,sym_fs(__page_tables_start)-8(,%ecx,8)
+1:      testl   $_PAGE_PRESENT,sym_fs(__page_tables_start)-8(,%ecx,8)
         jz      2f
         add     %esi,sym_fs(__page_tables_start)-8(,%ecx,8)
 2:      loop    1b
diff --git a/xen/arch/x86/boot/x86_64.S b/xen/arch/x86/boot/x86_64.S
index 0acf5e860c..de555f87f4 100644
--- a/xen/arch/x86/boot/x86_64.S
+++ b/xen/arch/x86/boot/x86_64.S
@@ -65,24 +65,19 @@ l1_identmap:
         .size l1_identmap, . - l1_identmap
 
 /*
- * __page_tables_start does not cover l1_identmap because it (l1_identmap)
- * contains 1-1 mappings. This means that frame addresses of these mappings
- * are static and should not be updated at runtime.
+ * __page_tables_{start,end} cover the range of pagetables which need
+ * relocating as Xen moves around physical memory.  i.e. each sym_offs()
+ * reference to a different pagetable in the Xen image.
  */
 GLOBAL(__page_tables_start)
 
 /*
- * Space for mapping the first 4GB of memory, with the first 16 megabytes
- * actualy mapped (mostly using superpages).  Uses 4x 4k pages.
+ * Space for 4G worth of 2M mappings, first 2M actually mapped via
+ * l1_identmap[].  Uses 4x 4k pages.
  */
 GLOBAL(l2_identmap)
         .quad sym_offs(l1_identmap) + __PAGE_HYPERVISOR
-        idx = 1
-        .rept 7
-        .quad (idx << L2_PAGETABLE_SHIFT) | PAGE_HYPERVISOR | _PAGE_PSE
-        idx = idx + 1
-        .endr
-        .fill 4 * L2_PAGETABLE_ENTRIES - 8, 8, 0
+        .fill 4 * L2_PAGETABLE_ENTRIES - 1, 8, 0
         .size l2_identmap, . - l2_identmap
 
 /*
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index ed54f79fea..62adc9e2a8 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -678,6 +678,9 @@ static unsigned int __init copy_bios_e820(struct e820entry *map, unsigned int li
     return n;
 }
 
+/* How much of the directmap is prebuilt at compile time. */
+#define PREBUILT_MAP_LIMIT (1 << L2_PAGETABLE_SHIFT)
+
 void __init noreturn __start_xen(unsigned long mbi_p)
 {
     char *memmap_type = NULL;
@@ -1020,7 +1023,7 @@ void __init noreturn __start_xen(unsigned long mbi_p)
      *
      * We require superpage alignment because the boot allocator is
      * not yet initialised. Hence we can only map superpages in the
-     * address range BOOTSTRAP_MAP_BASE to 4GB, as this is guaranteed
+     * address range PREBUILT_MAP_LIMIT to 4GB, as this is guaranteed
      * not to require dynamic allocation of pagetables.
      *
      * As well as mapping superpages in that range, in preparation for
@@ -1036,10 +1039,10 @@ void __init noreturn __start_xen(unsigned long mbi_p)
         if ( boot_e820.map[i].type != E820_RAM )
             continue;
 
-        /* Superpage-aligned chunks from BOOTSTRAP_MAP_BASE. */
+        /* Superpage-aligned chunks from PREBUILT_MAP_LIMIT. */
         s = (boot_e820.map[i].addr + mask) & ~mask;
         e = (boot_e820.map[i].addr + boot_e820.map[i].size) & ~mask;
-        s = max_t(uint64_t, s, BOOTSTRAP_MAP_BASE);
+        s = max_t(uint64_t, s, PREBUILT_MAP_LIMIT);
         if ( s >= e )
             continue;
 
@@ -1346,8 +1349,8 @@ void __init noreturn __start_xen(unsigned long mbi_p)
 
         set_pdx_range(s >> PAGE_SHIFT, e >> PAGE_SHIFT);
 
-        /* Need to create mappings above BOOTSTRAP_MAP_BASE. */
-        map_s = max_t(uint64_t, s, BOOTSTRAP_MAP_BASE);
+        /* Need to create mappings above PREBUILT_MAP_LIMIT. */
+        map_s = max_t(uint64_t, s, PREBUILT_MAP_LIMIT);
         map_e = min_t(uint64_t, e,
                       ARRAY_SIZE(l2_identmap) << L2_PAGETABLE_SHIFT);
 
diff --git a/xen/arch/x86/x86_64/asm-offsets.c b/xen/arch/x86/x86_64/asm-offsets.c
index f9cb78cfdb..07d2155bf5 100644
--- a/xen/arch/x86/x86_64/asm-offsets.c
+++ b/xen/arch/x86/x86_64/asm-offsets.c
@@ -165,8 +165,5 @@ void __dummy__(void)
     OFFSET(MB2_efi64_ih, multiboot2_tag_efi64_ih_t, pointer);
     BLANK();
 
-    DEFINE(l2_identmap_sizeof, sizeof(l2_identmap));
-    BLANK();
-
     OFFSET(DOMAIN_vm_assist, struct domain, vm_assist);
 }