diff -r ca0759a08057 -r 2b40508f7645 xen/drivers/passthrough/vtd/dmar.c
--- a/xen/drivers/passthrough/vtd/dmar.c	Fri Jan 22 11:01:18 2010 +0000
+++ b/xen/drivers/passthrough/vtd/dmar.c	Mon Jan 25 15:36:32 2010 +0900
@@ -396,8 +396,65 @@
 
     if ( ret )
         xfree(dmaru);
+    else if ( dmaru->include_all )
+        acpi_register_drhd_unit(dmaru);
     else
-        acpi_register_drhd_unit(dmaru);
+    {
+        u8 b, d, f;
+        int i, invalid_cnt = 0;
+
+        for ( i = 0; i < dmaru->scope.devices_cnt; i++ )
+        {
+            b = PCI_BUS(dmaru->scope.devices[i]);
+            d = PCI_SLOT(dmaru->scope.devices[i]);
+            f = PCI_FUNC(dmaru->scope.devices[i]);
+
+            if ( pci_device_detect(b, d, f) == 0 )
+            {
+                dprintk(XENLOG_WARNING VTDPREFIX,
+                    "  Non-existent device (%x:%x.%x) is reported "
+                    "in this DRHD's scope!\n", b, d, f);
+                invalid_cnt++;
+            }
+        }
+
+        /*
+         * If all devices under the scope of the DRHD are non-existent,
+         * this DRHD is invalid but safely ignorable, so ignore it.
+         * If some devices under the scope of the DRHD are non-existent,
+         * this DRHD is invalid, so disable VT-d unless "iommu=force"
+         * option is specified.
+         * When "iommu=force" option is specified, even the invalid DRHD
+         * will be registered, because DRHD that has some existent devices
+         * must not be ignored due to security reasons.
+         */
+        if ( invalid_cnt )
+        {
+            if ( invalid_cnt == dmaru->scope.devices_cnt )
+            {
+                dprintk(XENLOG_WARNING VTDPREFIX,
+                    "  Ignore the DRHD due to all devices under "
+                    "its scope are not PCI discoverable!\n");
+                xfree(dmaru);
+            }
+            else
+            {
+                dprintk(XENLOG_WARNING VTDPREFIX,
+                    "  The DRHD is invalid due to some devices under "
+                    "its scope are not PCI discoverable!\n");
+                if ( force_iommu )
+                    acpi_register_drhd_unit(dmaru);
+                else
+                {
+                    xfree(dmaru);
+                    ret = -EINVAL;
+                }
+            }
+        }
+        else
+            acpi_register_drhd_unit(dmaru);
+    }
+
     return ret;
 }
 
@@ -444,7 +501,7 @@
     else
     {
         u8 b, d, f;
-        int i, ignore = 0;
+        int i, invalid_cnt = 0;
 
         for ( i = 0; i < rmrru->scope.devices_cnt; i++ )
         {
@@ -458,24 +515,44 @@
                     "  Non-existent device (%x:%x.%x) is reported "
                     "in RMRR (%"PRIx64", %"PRIx64")'s scope!\n",
                     b, d, f, rmrru->base_address, rmrru->end_address);
-                ignore = 1;
+                invalid_cnt++;
+            }
+        }
+
+        /*
+         * If all devices under the scope of the RMRR are non-existent,
+         * this RMMR is invalid but ignorable, so ignore it.
+         * If some devices under the scope of the RMRR are non-existent,
+         * this RMRR is invalid, so disable VT-d unless "iommu=force"
+         * option is specified. When "iommu=force" option is specified,
+         * the invalid RMRR is ignored.
+         */
+        if ( invalid_cnt )
+        {
+            if ( invalid_cnt == rmrru->scope.devices_cnt )
+            {
+                dprintk(XENLOG_WARNING VTDPREFIX,
+                    "  Ignore the RMRR (%"PRIx64", %"PRIx64") due to "
+                    "devices under its scope are not PCI discoverable!\n",
+                    rmrru->base_address, rmrru->end_address);
+                xfree(rmrru);
+                return 0;
             }
             else
             {
-                ignore = 0;
-                break;
+                dprintk(XENLOG_WARNING VTDPREFIX,
+                    "  The RMRR (%"PRIx64", %"PRIx64") is invalid due to "
+                    "some devices under its scope are not PCI discoverable!\n",
+                    rmrru->base_address, rmrru->end_address);
+                if ( !force_iommu )
+                {
+                    xfree(rmrru);
+                    return -EINVAL;
+                }
             }
         }
 
-        if ( ignore )
-        {
-            dprintk(XENLOG_WARNING VTDPREFIX,
-                "  Ignore the RMRR (%"PRIx64", %"PRIx64") due to "
-                "devices under its scope are not PCI discoverable!\n",
-                rmrru->base_address, rmrru->end_address);
-            xfree(rmrru);
-        }
-        else if ( base_addr > end_addr )
+        if ( base_addr > end_addr )
         {
             dprintk(XENLOG_WARNING VTDPREFIX,
                 "  The RMRR (%"PRIx64", %"PRIx64") is incorrect!\n",