diff -rN -u -p old-xen-64/xen/include/asm-x86/e820.h new-xen-64/xen/include/asm-x86/e820.h
--- old-xen-64/xen/include/asm-x86/e820.h	2005-05-17 19:24:08.000000000 +0000
+++ new-xen-64/xen/include/asm-x86/e820.h	2005-05-18 21:09:40.000000000 +0000
@@ -36,4 +36,17 @@ extern void print_e820_memory_map(struct
 #define PFN_DOWN(x)   ((x) >> PAGE_SHIFT)
 #define PFN_UP(x)     (((x) + PAGE_SIZE-1) >> PAGE_SHIFT)
 
+static inline int pfn_valid(unsigned long pfn) {
+    int i;
+
+    for (i = 0; i < e820.nr_map; i++) {
+        if (pfn >= (e820.map[i].addr >> PAGE_SHIFT) &&
+            pfn < ((e820.map[i].addr & ~PAGE_MASK) +
+		   e820.map[i].size) >> PAGE_SHIFT)
+            return 1;
+    }
+
+    return 0;
+}
+
 #endif /*__E820_HEADER*/
diff -rN -u -p old-xen-64/xen/include/asm-x86/page.h new-xen-64/xen/include/asm-x86/page.h
--- old-xen-64/xen/include/asm-x86/page.h	2005-05-13 11:28:10.000000000 +0000
+++ new-xen-64/xen/include/asm-x86/page.h	2005-05-18 21:09:30.000000000 +0000
@@ -36,7 +36,6 @@ typedef struct { unsigned long pt_lo; } 
 #define pfn_to_page(_pfn)   (frame_table + (_pfn))
 #define phys_to_page(kaddr) (frame_table + ((kaddr) >> PAGE_SHIFT))
 #define virt_to_page(kaddr) (frame_table + (__pa(kaddr) >> PAGE_SHIFT))
-#define pfn_valid(_pfn)     ((_pfn) < max_page)
 
 /* High table entries are reserved by the hypervisor. */
 #define DOMAIN_ENTRIES_PER_L2_PAGETABLE     \