Enabling 64-bit VMs on nested ESXi 5.1

In my home lab, I have a 2-node cluster with two virtual ESXi 5.1. When I tried to boot a 64-bit on these hosts I received the following error:

"Longmode is unsupported. It is required for 64-bit guest OS support. On Intel systems, longmode requires VT-x to be enabled in the BIOS. On nested virtual ESX hosts, longmode requires the "Virtualized Hardware Virtualization" flag to be enabled on the outer VM."

I seem to remember that in version 5.0 you had to configure a given parameter in the ESXi console. For ESXi 5.1 this has changed according to this VMware KB.

It states the following:

"Virtualized HV is fully  supported for virtual hardware version 9 VMs on hosts that support  Intel VT-x and EPT or AMD-V and RVI. To enable virtualized HV, use the web client and navigate to the processor settings screen. Check the  box next to  "Expose hardware-assisted virtualization to the guest operating system."  This setting is not available under the traditional C# client."

So, access the web client, locate the VM, right click -> Edit settings, and check the box as mentioned (for the parent VM, not the virtual ESXi...). It works like a charm, see screendump below:

How to run XenServer 6.0 on vSphere 5 - with nested Windows Server 2008 R2 VM

It is possible to install XenServer 6.0 in a virtual machine on vSphere ESXi 5 and then with a few tweaks you can even run a nested Windows Server 2008 R2 VM on the virtual XenServer 6.0.

To install XenServer 6.0 in a VM, first follow this guide to configure ESXi 5.0 (or watch this youtube video).

One important step is to execute the following command from the console:

echo 'vhv.allow = "TRUE"' >> /etc/vmware/config

Otherwise, configure like the guide. Once the custom VM has been created, to be able to choose ESXi 5 as operating system, go to Edit Settings -> Options -> Guest Operating System choose 'Other' and then choose VMware ESXi 5.x. This will ensure that you won't receive the "HVM is required for this operation" error when trying to boot the win2k8R2 vm (it is possible to change this after the install of XenServer as well).

Download the install .iso from citrix.com 

Mount iso and install XenServer

When done, you will get startup screen as below

Download XenCenter from citrix.com and install

Add the the XenServer to XenCenter

Create a new VM, choose win2k8 R2 64-bit, mount ISO, install.

Done.