x86/boot: Better describe the pagetable relocation loops

The first loop relocates all reachable non-leaf entries in idle_pg_table[],
which includes l2_xenmap[511]'s reference to l1_fixmap_x[].

The second loop relocates only leaf mappings in l2_xenmap[], so update the
skip condition to be opposite to the first loop.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 6f241048425ce468500826a81dd62a377cdfb634..495b4b7d51fb4d7b11f4d9c1df5c0de7749384fd 100644 (file)
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -1245,7 +1245,7 @@ void __init noreturn __start_xen(unsigned long mbi_p)
             barrier();
             move_memory(e, XEN_IMG_OFFSET, _end - _start, 1);
 
-            /* Walk initial pagetables, relocating page directory entries. */
+            /* Walk idle_pg_table, relocating non-leaf entries. */
             pl4e = __va(__pa(idle_pg_table));
             for ( i = 0 ; i < L4_PAGETABLE_ENTRIES; i++, pl4e++ )
             {
@@ -1277,18 +1277,18 @@ void __init noreturn __start_xen(unsigned long mbi_p)
                 }
             }
 
-            /* The only data mappings to be relocated are in the Xen area. */
-            pl2e = __va(__pa(l2_xenmap));
-
             BUG_ON(using_2M_mapping() &&
                    l2_table_offset((unsigned long)_erodata) ==
                    l2_table_offset((unsigned long)_stext));
 
+            /* Walk l2_xenmap[], relocating 2M superpage leaves. */
+            pl2e = __va(__pa(l2_xenmap));
             for ( i = 0; i < L2_PAGETABLE_ENTRIES; i++, pl2e++ )
             {
                 unsigned int flags;
 
                 if ( !(l2e_get_flags(*pl2e) & _PAGE_PRESENT) ||
+                     !(l2e_get_flags(*pl2e) & _PAGE_PSE) ||
                      (l2e_get_pfn(*pl2e) >= pte_update_limit) )
                     continue;