Hyper-V Cannot Be Installed: A Hypervisor Is Already Running | Server 2012

I’ve been trying to install the Hyper-V role on a Windows 2012 Server, but got the following error message:

Validation Results

The validation process found problems on the server to which you want to install features. The selected features are not compatible with the current configuration of your selected server. Click OK to select different features.

Hyper-V cannot be installed: A hypervisor is already running.

At first I thought that this was because I had installed Remote Desktop Services. My line of thinking was that as RDS has a Virtual Desktop Infrastructure option, it would already have some sort of hypervisor already running for the VDI… Even though I hadn’t installed the VDI option in my Remote Desktop Services installation.

Upon some investigation, it seems that a brand new installation of Windows Server 2012 on VMware ESXi doesn’t allow me to install Hyper-V and it’s nothing to do with Terminal Server or VDI already running.

The fix for this error was to power down the VM that I wanted to install Hyper-V on and edit the VMware VMX file to say:

hypervisor.cpuid.v0 = “FALSE”

Unfortunately you will now get a message regarding HAL_Memory_Allocation when you start Windows. To get around this, you also need to add this line to the VMX file before powering on the VM:

mce.enable = “TRUE”

This will clear up the message saying that you cannot install Hyper-V because a hypervisor is already running, in favour of this error:

Hyper-v cannot be installed: the processor does not have required virtualization capabilities

This is now telling you that your processor isn’t capable of running a VM because it’s not an x64 CPU that supports DEP and hardware assisted virtualisation. Even if you do have a processor that fits the requirements for virtualisation, you cannot install Hyper-V on VMware ESXi because ESXi doesn’t pass the virtualisation features through to the VM. I assume that RDS VDI uses Hyper-V (Although I haven’t done enough research into this to be sure), so presumably this means that you cannot run RD VDI on VMware ESXi 4 and 5 at this stage.

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