diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index 68cb72a481..90cd4e5044 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -2763,17 +2763,6 @@ static bool vtd_process_inv_desc(IntelIOMMUState *s)
         }
         break;
 
-    /*
-     * TODO: the entity of below two cases will be implemented in future series.
-     * To make guest (which integrates scalable mode support patch set in
-     * iommu driver) work, just return true is enough so far.
-     */
-    case VTD_INV_DESC_PC:
-        break;
-
-    case VTD_INV_DESC_PIOTLB:
-        break;
-
     case VTD_INV_DESC_WAIT:
         trace_vtd_inv_desc("wait", inv_desc.hi, inv_desc.lo);
         if (!vtd_process_wait_desc(s, &inv_desc)) {
@@ -2795,6 +2784,17 @@ static bool vtd_process_inv_desc(IntelIOMMUState *s)
         }
         break;
 
+    /*
+     * TODO: the entity of below two cases will be implemented in future series.
+     * To make guest (which integrates scalable mode support patch set in
+     * iommu driver) work, just return true is enough so far.
+     */
+    case VTD_INV_DESC_PC:
+    case VTD_INV_DESC_PIOTLB:
+        if (s->scalable_mode) {
+            break;
+        }
+    /* fallthrough */
     default:
         error_report_once("%s: invalid inv desc: hi=%"PRIx64", lo=%"PRIx64
                           " (unknown type)", __func__, inv_desc.hi,