diff -r 806e66a6cb1a xen/drivers/passthrough/vtd/dmar.c
--- a/xen/drivers/passthrough/vtd/dmar.c	Wed Jul 16 13:57:34 2008 +0100
+++ b/xen/drivers/passthrough/vtd/dmar.c	Thu Jul 17 15:58:44 2008 +0800
@@ -349,6 +349,9 @@ acpi_parse_one_rmrr(struct acpi_dmar_ent
     void *dev_scope_start, *dev_scope_end;
     int ret = 0;
 
+    if ( rmrr->base_address >= rmrr->end_address )
+        return -EFAULT;
+
     rmrru = xmalloc(struct acpi_rmrr_unit);
     if ( !rmrru )
         return -ENOMEM;