Using hardware-assisted virtualization in Windows Server 2003 32-bit virtual machines

Products

• VMware vSphere ESXi

Issue/Introduction

This article provides information on using hardware-assisted virtualization (Intel VT-x or AMD-V) in Windows Server 2003 SP2 virtual machines.

This feature is not enabled by default. This can be enabled on Intel ESXi hosts to support hardware-assisted virtualization on the virtual machines.

Environment

VMware ESXi 4.0.x Embedded
VMware ESX 4.0.x
VMware ESX 4.1.x
VMware ESXi 4.1.x Installable
VMware ESXi 4.1.x Embedded
VMware ESXi 4.0.x Installable

Resolution

Earlier 32-bit operating systems such as Windows XP and Windows Server 2003 (pre-SP2) access the Task Priority Register (TPR) very frequently. These operations are performed much faster using Binary Translation than hardware-assisted virtualization. Setting hardware-assisted virtualization caused a performance impact, rather than a performance gain.

When using Windows 2003 SP2 or higher, a pre-SP2 compatibility mode is leveraged which uses Binary Translation instead of Hardware CPU/MMU Virtualization. Hardware-assisted virtualization can be enabled on Windows Server 2003 SP2 or higher with a significant performance gain, depending on the workload.

On vSphere ESX/ESXi 4.1 and ESXi 5.0 and 5.1, confirm the ESX/ESXi host has the appropriate updates outlined in ESXi/ESX host fails with a purple diagnostic screen that displays: TimerAlloc (2042684).

To enable hardware-assisted virtualization for the virtual machine:

1. In the vSphere Client inventory, right-click the virtual machine and click Edit Settings.
2. Click the Options tab.
   
3. Under Advanced select CPU/MMU Virtualization.
4. Select either hardware support for CPU virtualization, or both CPU and MMU virtualization.
5. Click OK to save your changes and close the dialog box.
   
   For more information, see the Configuring Virtual Machines: Virtual Machine Hardware, Options, and Resources Available to vSphere Virtual Machines: CPU Virtual Machine Configuration: Change CPU/MMU Virtualization Settings section in the vSphere Virtual Machine Administration Guide for your version of vSphere.
   
   

Additional Information

ESXi/ESX host fails with a purple diagnostic screen that displays: TimerAlloc