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:

ESX 4.0 in Workstation - requires Intel-VT

I have been running ESX 3.5 and ESX 4.0 in VMware Workstation 6.5.1 for a while on my Lenovo T61 from work without any problems. A prerequisite for doing this, at least for ESX 4.0 (an probably also for Hyper-V) as it runs 64-bit, is that the CPU supports virtualisation mode - which in the Intel terminology is called Intel-VT - an which has to be enabled in the BIOS. The T61 is about one year old and has Intel-VT, so I thought that it was standard on all newer Intel processors. But oh-no, this is not the case. I recently purchased a Dell Studio 17 for private use with a Intel Core Duo 2 T6400 processor and I thought that I was in the good house. But - no Intel-VT support. Everything else was in order, 4 GB of memory, Windows 7 64-bit and so on. This was a bit disappointing. If your're looking to buy a new laptop, then check that this feature comes with the CPU. I found an article on ZDnet which lists a number of processors and wheather they have Intel-VT enabled.

The following has been copied from the ZDnet article. YES means that the CPU type supports Intel-VT:

Update: Here's a link to Intel's page with Intel-VT technology list

How to enable 64-bit in BIOS on HP server

To be able to run 64-bit VM's in VMware ESX server, then Intel-VT technology needs to be enable in BIOS. Furthermore, to enable EVC (Enhanced VMotion Compability), No-execute memory feature should be enabled, see below.

1. Go to BIOS (press F9 during boot)
2. Go to Advanced Options -> Processor Options -> Intel ® Virtualization Technology
3. Choose Enable
4. Furtermore, to enable VMware EVC, enable 'No-Execute Memory Protection' (just above Intel-VT).
5. Save and exit


NB: All hosts in your cluster should have the same BIOS settings. If not, this can result in VMotion issues.