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<chapter id="KnownIssues">

<title>Known limitations</title>

<sect1 id="ExperimentalFeatures">

<title>Experimental Features</title>

<para>Some VirtualBox features are labeled as experimental. Such

features are provided on an "as-is" basis and are not formally

supported. However, feedback and suggestions about such features are

welcome. A comprehensive list of experimental features follows:</para>

<itemizedlist>

<listitem>

WDDM Direct3D video driver for Windows guests

</listitem>

<listitem>

Hardware 3D acceleration support for Windows, Linux, and Solaris

guests

</listitem>

<listitem>

Hardware 2D video playback acceleration support for Windows

guests

</listitem>

<listitem>

PCI pass-through (Linux hosts only)

</listitem>

<listitem>

Mac OS X guests (Mac hosts only)

</listitem>

<listitem>

ICH9 chipset emulation

</listitem>

<listitem>

EFI firmware

</listitem>

<listitem>

Host CD/DVD drive pass-through

</listitem>

<listitem>

Support of iSCSI via internal networking

</listitem>

<listitem>

Synthetic CPU reporting

</listitem>

</itemizedlist>

</sect1>

<sect1 id="KnownProblems">

<title>Known Issues</title>

<para>The following section describes known problems with VirtualBox

$VBOX_VERSION_STRING. Unless marked otherwise, these issues are planned to

be fixed in later releases.</para>

<itemizedlist>

<listitem>

<para>The following <emphasis role="bold">Guest SMP (multiprocessor)

limitations</emphasis> exist:<itemizedlist>

<listitem>

<para><emphasis role="bold">Poor performance</emphasis> with

32-bit guests on AMD CPUs. This affects mainly Windows and Solaris

guests, but possibly also some Linux kernel revisions. Partially

solved in 3.0.6 for 32 bits Windows NT, 2000, XP and 2003 guests.

Requires 3.0.6 or higher Guest Additions to be installed.</para>

</listitem>

<listitem>

<para><emphasis role="bold">Poor performance</emphasis> with

32-bit guests on certain Intel CPU models that do not include

virtual APIC hardware optimization support. This affects mainly

Windows and Solaris guests, but possibly also some Linux kernel

revisions. Partially solved in 3.0.12 for 32 bits Windows NT,

2000, XP and 2003 guests. Requires 3.0.12 or higher Guest

Additions to be installed.</para>

</listitem>

</itemizedlist></para>

</listitem>

<listitem>

<para><emphasis role="bold">64-bit guests on some 32-bit host systems

with VT-x</emphasis> can cause instabilities to your system. If you

experience this, do not attempt to execute 64-bit guests. Refer to the

VirtualBox user forum for additional information.</para>

</listitem>

<listitem>

<para>For <emphasis role="bold">basic Direct3D support in Windows

guests</emphasis> to work, the Guest Additions must be installed in

Windows "safe mode". Press F8 when the Windows guest is booting and

select "Safe mode", then install the Guest Additions. Otherwise Windows'

file protection mechanism will interfere with the replacement DLLs

installed by VirtualBox and keep restoring the original Windows system

DLLs. <note>

<para>This does <emphasis role="bold">not</emphasis> apply to the

experimental WDDM Direct3D video

driver available for Vista and Windows 7 guests shipped with

VirtualBox 4.1.</para>

</note></para>

</listitem>

<listitem>

<para><emphasis role="bold">Guest control.</emphasis> On Windows guests,

a process lauched via the guest control execute support will not be able

to display a graphical user interface <emphasis>unless</emphasis> the

user account under which it is running is currently logged in and has a

desktop session.</para>

<para>Also, to use accounts without or with an empty password, the

guest's group policy must be changed. To do so, open the group policy

editor on the command line by typing

<computeroutput>gpedit.msc</computeroutput>, open the key

<emphasis>Computer Configuration\Windows Settings\Security

Settings\Local Policies\Security Options</emphasis> and change the value

of <emphasis>Accounts: Limit local account use of blank passwords to

console logon only</emphasis> to <emphasis>Disabled</emphasis>.</para>

</listitem>

<listitem>

<para><emphasis role="bold">Compacting virtual disk images is limited to

VDI files.</emphasis> The <code>VBoxManage modifyhd --compact</code>

command is currently only implemented for VDI files. At the moment the

only way to optimize the size of a virtual disk images in other formats

(VMDK, VHD) is to clone the image and then use the cloned image in the

VM configuration.</para>

</listitem>

<listitem>

<para><emphasis role="bold">OVF import/export:</emphasis><itemizedlist>

<listitem>

<para>OVF localization (multiple languages in one OVF file) is not

yet supported.</para>

</listitem>

<listitem>

<para>Some OVF sections like StartupSection,

DeploymentOptionSection and InstallSection are ignored.</para>

</listitem>

<listitem>

<para>OVF environment documents, including their property sections

and appliance configuration with ISO images, are not yet

supported.</para>

</listitem>

<listitem>

<para>Remote files via HTTP or other mechanisms are not yet

supported.</para>

</listitem>

</itemizedlist></para>

</listitem>

<listitem>

<para>Neither <emphasis role="bold">scale mode</emphasis> nor <emphasis

role="bold">seamless mode</emphasis> work correctly with guests using

OpenGL 3D features (such as with compiz-enabled window managers).</para>

</listitem>

<listitem>

<para>Preserving the aspect ratio in scale mode works only on Windows

hosts and on Mac OS X hosts.</para>

</listitem>

<listitem>

<para>On <emphasis role="bold">Mac OS X hosts,</emphasis> the following

features are not yet implemented:</para>

<para><itemizedlist>

<listitem>

<para>Numlock emulation</para>

</listitem>

<listitem>

<para>CPU frequency metric</para>

</listitem>

<listitem>

<para>Memory ballooning</para>

</listitem>

</itemizedlist></para>

</listitem>

<listitem>

<para><emphasis role="bold">Mac OS X guests:</emphasis>

<itemizedlist>

<listitem>

<para>Mac OS X guests can only run on a certain host hardware.

For details about license and host hardware limitations, please

see <xref linkend="intro-macosxguests" /> and check the Apple

software license conditions.</para>

</listitem>

<listitem>

<para>VirtualBox does not provide Guest Additions for Mac OS X

at this time.</para>

</listitem>

<listitem>

<para>The graphics resolution currently defaults to 1024x768 as

Mac OS X falls back to the built-in EFI display support. See

<xref linkend="efividmode" /> for more information on how to

change EFI video modes.</para>

</listitem>

<listitem>

<para>Even when idle, Mac OS X guests currently burn 100% CPU.

This is a power management issue that will be addressed in a

future release.</para>

</listitem>

<listitem>

<para>Mac OS X guests only work with one CPU assigned to the

VM. Support for SMP will be provided in a future release.</para>

</listitem>

<listitem>

<para>Depending on your system and version of Mac OS X, you

might experience guest hangs after some time. This can be fixed

by turning off energy saving (set timeout to "Never") in the

system preferences.</para>

</listitem>

<listitem>

<para>By default, the VirtualBox EFI enables debug output of the

Mac OS X kernel to help you diagnose boot problems. Note that

there is a lot of output and not all errors are fatal (they

would also show on your physical Mac). You can turn off these

messages by issuing this command:<screen>VBoxManage setextradata "VM name" "VBoxInternal2/EfiBootArgs" " "</screen>To

revert to the previous behavior, use:<screen>VBoxManage setextradata "VM name" "VBoxInternal2/EfiBootArgs" ""</screen></para>

</listitem>

</itemizedlist></para>

</listitem>

<listitem>

<para><emphasis role="bold">Solaris hosts:</emphasis> <itemizedlist>

<listitem>

<para>There is no support for USB devices connected to Solaris 10

hosts.</para>

</listitem>

<listitem>

<para>USB support on Solaris hosts requires Solaris 11 version

snv_124 or higher. Webcams and other isochronous devices are known

to have poor performance.</para>

</listitem>

<listitem>

<para>No ACPI information (battery status, power source) is

reported to the guest.</para>

</listitem>

<listitem>

<para>No support for using wireless adapters with bridged

networking.</para>

</listitem>

<listitem>

<para>Crossbow based bridged networking on Solaris 11 hosts does

not work directly with aggregate links. However, you can manually

create a VNIC (using <computeroutput>dladm</computeroutput>) over

the aggregate link and use that with a VM. This technical

limitation between VirtualBox and Solaris will be addressed in a

future release.</para>

</listitem>

</itemizedlist></para>

</listitem>

<listitem>

<para><emphasis role="bold">Guest Additions of version 4.1, 4.1.2 and 4.1.4 for Windows</emphasis>

Thus VirtualBox WDDM Video driver may be installed and kept in guest system

if Guest additions uninstallation is performed.

This is caused by a bug in Guest Additions uninstaller.

<note>

<para>This does <emphasis role="bold">not</emphasis> apply to Guest Additions update,

i.e. installing a one version of Guest Additions on top of another works correctly.</para>

</note>

To solve this problem, one should uninstall the VirtualBox WDDM Video driver manually.

To do that open Device Manager, and check whether the Display Adapter is named

"VirtualBox Graphics Adapter ..". If no - there is nothing to be done. If yes - right-clik

the VirtualBox Graphics Adapter in Device Manager, select "Uninstall", check "Delete the driver software for this device"

and click "OK". Once uninstallation is done - in Device Manager go to menu "Action" and select

"Scan for hardware changes" to make the propper (Windows default) driver be picked up for the Graphics adapter.

</para>

</listitem>

<listitem>

<para>Neither <emphasis>virtio</emphasis> nor <emphasis>Intel PRO/1000

</emphasis> drivers for <emphasis role="bold">Windows XP guests

</emphasis> do not support segmentation offloading. Therefore

Windows XP guests have slower transmission rates comparing to other

guest types. Refer to MS Knowledge base article 842264 for additional

information.</para>

</listitem>

<listitem>

<para><emphasis role="bold">Guest Additions for OS/2.</emphasis> Shared

folders are not yet supported with OS/2 guests. In addition, seamless

windows and automatic guest resizing will probably never be implemented

due to inherent limitations of the OS/2 graphics system.</para>

</listitem>

</itemizedlist>

</sect1>

</chapter>