Index: /trunk/doc/manual/en_US/man_VBoxManage-storagectl.xml
===================================================================
--- /trunk/doc/manual/en_US/man_VBoxManage-storagectl.xml	(revision 82351)
+++ /trunk/doc/manual/en_US/man_VBoxManage-storagectl.xml	(revision 82352)
@@ -64,4 +64,5 @@
           <arg choice="plain">PIIX4</arg>
           <arg choice="plain">USB</arg>
+          <arg choice="plain">VirtIO</arg>
         </group></arg>
       <arg>--bootable=<group choice="plain">
Index: /trunk/doc/manual/en_US/user_Storage.xml
===================================================================
--- /trunk/doc/manual/en_US/user_Storage.xml	(revision 82351)
+++ /trunk/doc/manual/en_US/user_Storage.xml	(revision 82352)
@@ -59,6 +59,6 @@
       operation and data transfers. &product-name; can emulate the most
       common types of hard disk controllers typically found in computing
-      devices: IDE, SATA (AHCI), SCSI, SAS, USB-based, and NVMe mass
-      storage devices.
+      devices: IDE, SATA (AHCI), SCSI, SAS, USB-based, NVMe and
+      virtio-scsi mass storage devices.
     </para>
 
@@ -309,4 +309,23 @@
       </listitem>
 
+      <listitem>
+        <para>
+          <emphasis role="bold">Virtual I/O Device SCSI</emphasis> is a
+          standard to connect virtual storage devices like hard disks or
+          optical drives to a VM. Recent Linux and Windows versions
+          support these devices (Windows needs additional drivers).
+          Currently the virtio-scsi controller is experimental.
+        </para>
+
+        <warning>
+          <para>
+            The virtio-scsi controller will only be seen by OSes with
+            device support for it. In particular, <emphasis>there is
+            no built-in support in Windows</emphasis>. So Windows will
+            not see such disks unless you install additional drivers.
+          </para>
+        </warning>
+      </listitem>
+
     </itemizedlist>
 
@@ -357,4 +376,11 @@
         <para>
           Up to 255 slots attached to the NVMe controller, if enabled
+          and supported by the guest OS.
+        </para>
+      </listitem>
+
+      <listitem>
+        <para>
+          Up to 256 slots attached to the virtio-scsi controller, if enabled
           and supported by the guest OS.
         </para>
Index: /trunk/doc/manual/en_US/user_VBoxManage.xml
===================================================================
--- /trunk/doc/manual/en_US/user_VBoxManage.xml	(revision 82351)
+++ /trunk/doc/manual/en_US/user_VBoxManage.xml	(revision 82352)
@@ -4968,5 +4968,5 @@
                             [--controller LSILogic|LSILogicSAS|BusLogic|
                                           IntelAhci|PIIX3|PIIX4|ICH6|I82078|
-                                          USB|NVMe]
+                                          USB|NVMe|VirtIO]
                             [--portcount &lt;1-30&gt;]
                             [--hostiocache on|off]
Index: /trunk/src/VBox/Main/src-server/SystemPropertiesImpl.cpp
===================================================================
--- /trunk/src/VBox/Main/src-server/SystemPropertiesImpl.cpp	(revision 82351)
+++ /trunk/src/VBox/Main/src-server/SystemPropertiesImpl.cpp	(revision 82352)
@@ -1576,7 +1576,5 @@
         StorageBus_USB,
         StorageBus_PCIe,
-#ifdef DEBUG
         StorageBus_VirtioSCSI,
-#endif
     };
     aSupportedStorageBuses.assign(aStorageBuses,
@@ -1599,7 +1597,5 @@
         StorageControllerType_USB,
         StorageControllerType_NVMe,
-#ifdef DEBUG
         StorageControllerType_VirtioSCSI,
-#endif
     };
     aSupportedStorageControllerTypes.assign(aStorageControllerTypes,