1 files changed, 16 insertions, 8 deletions

diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
index 9f42d7e9c158..f4c95aec5acb 100644
--- a/arch/x86/mm/ioremap.c
+++ b/arch/x86/mm/ioremap.c
@@ -42,6 +42,22 @@ int page_is_ram(unsigned long pagenr)
         unsigned long addr, end;
         int i;
 
+        /*
+         * A special case is the first 4Kb of memory;
+         * This is a BIOS owned area, not kernel ram, but generally
+         * not listed as such in the E820 table.
+         */
+        if (pagenr == 0)
+                return 0;
+
+        /*
+         * Second special case: Some BIOSen report the PC BIOS
+         * area (640->1Mb) as ram even though it is not.
+         */
+        if (pagenr >= (BIOS_BEGIN >> PAGE_SHIFT) &&
+                    pagenr < (BIOS_END >> PAGE_SHIFT))
+                return 0;
+
         for (i = 0; i < e820.nr_map; i++) {
                 /*
                  * Not usable memory:
@@ -51,14 +67,6 @@ int page_is_ram(unsigned long pagenr)
                 addr = (e820.map[i].addr + PAGE_SIZE-1) >> PAGE_SHIFT;
                 end = (e820.map[i].addr + e820.map[i].size) >> PAGE_SHIFT;
 
-                /*
-                 * Sanity check: Some BIOSen report areas as RAM that
-                 * are not. Notably the 640->1Mb area, which is the
-                 * PCI BIOS area.
-                 */
-                if (addr >= (BIOS_BEGIN >> PAGE_SHIFT) &&
-                    end < (BIOS_END >> PAGE_SHIFT))
-                        continue;
 
                 if ((pagenr >= addr) && (pagenr < end))
                         return 1;