Index: /trunk/src/VBox/Devices/Bus/DevIommuAmd.cpp
===================================================================
--- /trunk/src/VBox/Devices/Bus/DevIommuAmd.cpp	(revision 84307)
+++ /trunk/src/VBox/Devices/Bus/DevIommuAmd.cpp	(revision 84308)
@@ -4678,5 +4678,20 @@
         case IOMMU_CMD_INV_IOTLB_PAGES:
         case IOMMU_CMD_INV_INTR_TABLE:
+        {
+            return VERR_NOT_IMPLEMENTED;
+        }
+
         case IOMMU_CMD_PREFETCH_IOMMU_PAGES:
+        {
+            if (pThis->ExtFeat.n.u1PrefetchSup)
+            {
+                /** @todo IOMMU: Implement prefetch. */
+                return VINF_SUCCESS;
+            }
+            iommuAmdInitIllegalCmdEvent(GCPhysCmd, &EvtIllegalCmdErr);
+            iommuAmdRaiseIllegalCmdEvent(pDevIns, &EvtIllegalCmdErr, kIllegalCmdErrType_CmdNotSupported);
+            return VERR_INVALID_FUNCTION;
+        }
+
         case IOMMU_CMD_COMPLETE_PPR_REQ:
         case IOMMU_CMD_INV_IOMMU_ALL:
@@ -5505,8 +5520,4 @@
     pThis->EvtLogBBaseAddr.u64       = 0;
     pThis->EvtLogBBaseAddr.n.u4Len   = 8;
-
-    pThis->DevSpecificFeat.u64       = 0;
-    pThis->DevSpecificCtrl.u64       = 0;
-    pThis->DevSpecificStatus.u64     = 0;
 
     pThis->MsiMiscInfo.u64           = 0;
@@ -5796,4 +5807,8 @@
 
     pThis->RsvdReg = 0;
+
+    pThis->DevSpecificFeat.u64   = 0;
+    pThis->DevSpecificCtrl.u64   = 0;
+    pThis->DevSpecificStatus.u64 = 0;
 
     /*