x86,xen: introduce x86_init.mapping.pagetable_reserve
[linux-2.6.git] / arch / x86 / mm / init.c
index 286d289..722a4c3 100644 (file)
@@ -81,6 +81,11 @@ static void __init find_early_table_space(unsigned long end, int use_pse,
                end, pgt_buf_start << PAGE_SHIFT, pgt_buf_top << PAGE_SHIFT);
 }
 
+void native_pagetable_reserve(u64 start, u64 end)
+{
+       memblock_x86_reserve_range(start, end, "PGTABLE");
+}
+
 struct map_range {
        unsigned long start;
        unsigned long end;
@@ -272,9 +277,24 @@ unsigned long __init_refok init_memory_mapping(unsigned long start,
 
        __flush_tlb_all();
 
+       /*
+        * Reserve the kernel pagetable pages we used (pgt_buf_start -
+        * pgt_buf_end) and free the other ones (pgt_buf_end - pgt_buf_top)
+        * so that they can be reused for other purposes.
+        *
+        * On native it just means calling memblock_x86_reserve_range, on Xen it
+        * also means marking RW the pagetable pages that we allocated before
+        * but that haven't been used.
+        *
+        * In fact on xen we mark RO the whole range pgt_buf_start -
+        * pgt_buf_top, because we have to make sure that when
+        * init_memory_mapping reaches the pagetable pages area, it maps
+        * RO all the pagetable pages, including the ones that are beyond
+        * pgt_buf_end at that time.
+        */
        if (!after_bootmem && pgt_buf_end > pgt_buf_start)
-               memblock_x86_reserve_range(pgt_buf_start << PAGE_SHIFT,
-                                pgt_buf_end << PAGE_SHIFT, "PGTABLE");
+               x86_init.mapping.pagetable_reserve(PFN_PHYS(pgt_buf_start),
+                               PFN_PHYS(pgt_buf_end));
 
        if (!after_bootmem)
                early_memtest(start, end);