Windows Server 2008 R2 SP1 Does Not Support the AMD Bulldozer CPU’s AVX Feature

Windows Server 2008 R2 does not support the Advanced Vector Extensions (AVX) feature which was recently introduced in AMD’s Bulldozer CPU’s.

This detail has not changed with the advent of Service Pack 1, since Windows Server 2008 R2 SP1 is also not playing nice with AVX.

As a direct result, customers running Microsoft’s latest iteration of Windows Server can come across issues when attempting to use virtual machines under Hyper-V on a Windows Server 2008 R2 SP1 computer powered by an AMD CPU featuring AVX.

This will only happen when VMs are launched on machines equipped with Bulldozer-based multicore processors under the hypervisor role of Windows Server 2008 R2 SP1.

If “you create a virtual machine on the computer, and then you try to start the virtual machine, (…) the virtual machine does not start, and you receive the following error message: Virtual machine could not start because the hypervisor is not running,” Microsoft said.

“Additionally, the following event is added to the Microsoft-Windows-Hyper-V-Worker-Admin log: Source: Microsoft-Windows-Hyper-V-Worker, Event ID: 3112, Level: Error, Description: The virtual machine could not be started because the hypervisor is not running.”

According to the software giant the problem is generated by the fact that Windows Server 2008 R2 SP1 does not come with support for AVX feature on AMD chips.

A very simple workaround for this problem is to disable the AVX feature. Customers can do so by firing up cmd and entering the following command: bcdedit /set xsavedisable 1.

Windows Server 2008 R2 is affected by a similar problem, although the error message returned is a bit different: “Virtual machine name could not initialize.”

As a workaround, the Redmond company advices customers to “Start Hyper-V Manager. Right-click the virtual machine in question, and then click Settings. Under the Processor configuration for the virtual machine, click to select the Migrate to a physical computer with a different processor version check box, and then click OK. Start the virtual machine.”

In both cases however, users impacted by the problems describe above can download a hotfix from Microsoft. It appears that support for AMD Bulldozer CPU’s AVX feature will be introduced in Windows Server 2008 R2 SP2.

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