x86, mm: Fixup code testing if a pfn is direct mapped

Update code that previously assumed pfns [ 0 - max_low_pfn_mapped ) and
[ 4GB - max_pfn_mapped ) were always direct mapped, to now look up
pfn_mapped ranges instead.

-v2: change applying sequence to keep git bisecting working.
     so add dummy pfn_range_is_mapped(). - Yinghai Lu

Signed-off-by: Jacob Shin <jacob.shin@amd.com>
Link: http://lkml.kernel.org/r/1353123563-3103-12-git-send-email-yinghai@kernel.org
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index ad443914..36e53f0 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -835,7 +835,7 @@
 	efi_memory_desc_t *md, *prev_md = NULL;
 	efi_status_t status;
 	unsigned long size;
-	u64 end, systab, end_pfn;
+	u64 end, systab, start_pfn, end_pfn;
 	void *p, *va, *new_memmap = NULL;
 	int count = 0;
 
@@ -888,10 +888,9 @@
 		size = md->num_pages << EFI_PAGE_SHIFT;
 		end = md->phys_addr + size;
 
+		start_pfn = PFN_DOWN(md->phys_addr);
 		end_pfn = PFN_UP(end);
-		if (end_pfn <= max_low_pfn_mapped
-		    || (end_pfn > (1UL << (32 - PAGE_SHIFT))
-			&& end_pfn <= max_pfn_mapped)) {
+		if (pfn_range_is_mapped(start_pfn, end_pfn)) {
 			va = __va(md->phys_addr);
 
 			if (!(md->attribute & EFI_MEMORY_WB))