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Nested Virtualization APIs For vSphere & vCloud Director 5.1

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Did you know with the release of vSphere 5.1 and vCloud Director 5.1, there are now APIs that allow you to enable/disable Nested Virtualization aka (Virtual Hardware Virtualization) on a Virtual Machine?

Disclaimer: Nested Virtualization is not officially supported by VMware.

In the vSphere 5.1 API, there are two new properties related to Nested Virtualization:

  • nestedHVSupported is a new capability property which indicates whether your physical ESXi 5.1 host supports Nested Virtualization. This property is only true IF your physical CPU supports BOTH Intel-VT/EPT OR AMD-V/RVI. For more details, please refer to this article.
  • nestedHVEnabled is new property on a Virtual Machine which allows you to enable or disable Nested Virtualization. You will need to ensure you are running a Virtual Machine with ESXi 5.1 Compatibility (e.g. virtual hardware 9) and your physical ESXi 5.1 host supports Nested Virtualization.

Here is a screenshot of performing the same operation manually using the new vSphere Web Client:

In the vCloud Director 5.1 REST API, there two new operations related to Nested Virtualization:

  • /action/enableNestedHypervisor is a new operation on a Virtual Machine that enables Nested Virtualization. Here is an example using the curl utility enable VHV:

    curl -i -k -H "Accept:application/*+xml;version=5.1" -H "x-vcloud-authorization: xX4IrWWi+Ofq77zOqPJaMEYHHJt4jxrwP+ntkO2tecQ=" -X POST https://vcd.primp-industries.com/api/vApp/vm-d9870545-a29a-4175-bff4-ae075f1c1bc0/action/enableNestedHypervisor

  •  /action/disableNestedHypervisor is a new operation on a Virtual Machine that disables Nested Virtualization. Here is an example using the curl utility to disable VHV:

    curl -i -k -H "Accept:application/*+xml;version=5.1" -H "x-vcloud-authorization: xX4IrWWi+Ofq77zOqPJaMEYHHJt4jxrwP+ntkO2tecQ=" -X POST https://vcd.primp-industries.com/api/vApp/vm-d9870545-a29a-4175-bff4-ae075f1c1bc0/action/disableNestedHypervisor

Here is a screenshot of performing the same operation manually using the vCloud Director UI:

If you plan to leverage Nested Virtualization in your environment, you now have simple way of automating this feature for Virtual Machines that you wish to support Nested Virtualization.

Having Difficulties Enabling Nested ESXi in vSphere 5.1?

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I noticed there were a few folks having some difficulties enabling Nested ESXi (VHV Virtual Hardware Virtualization) in the latest release of ESXi 5.1 and I thought I share some additional info and tips on troubleshooting your setup in case you are running into similar problems.

*** DISCLAIMER **** This is not officially supported by VMware, do not bother asking if it is supported or calling into VMware support for details or help.

If you wish to run nested ESXi or other hypervisors on ESXi 5.1 and run 32-bit nested virtual machines, you must meet the following hardware requirement:

  • CPU supporting Intel VT-x or AMD-V

If you wish to run nested 64-bit virtual machines in your nested ESXi or other hypervisors, in addition to the requirement above, you must also meet the following hardware requirement:

  • CPU supporting Intel EPT or AMD RVI

If you only meet the first criteria, you CAN still install nested ESXi or other hypervisors on ESXi 5.1, BUT you will only be able to run 32-bit nested virtual machines. When you create your virtual machine shell using the new vSphere Web Client, in the expanded CPU view, the "Hardware Virtualization" box will be grayed out. This is expected as you do not have full support for VHV, but you can still continue with your installation of ESXi or other hypervisors.

In ESXi 5.0, you may have been able to run 64-bit nested virtual machines without EPT/RVI support but performance was extremely poor. With ESXi 5.1, VHV now requires EPT/RVI.

Note: During the installation of ESXi, you may see the following message "No Hardware Virtualization Support", you can just ignore it.

If you are using sites such as Intel's ark.intel.com to check your CPU requirements, be aware that it is COMMON even for the hardware vendors to publish incorrect information about their websites. However, there is a quick way you can validate on your ESXi host whether you have full VHV support.

In vSphere 5.1, there is a new capability property called nestedHVSupported which specifies whether your physical ESXi 5.1 host has full VHV support. This property will only be true IF your CPU has both Intel-VT+EPT or AMD-V+RVI. A quick and easy way to validate this is using the vSphere MOB to retrieve the value.

To check nestedHVSupported property, please enter the following into a web browser (substitute the IP Address/hostname of your ESXi host):

https://himalaya.primp-industries.com/mob/?moid=ha-host&doPath=capability

After you login, search for the nestedHVSupported property on the page and you should see a value of either true or false. As mentioned earlier, if it is false, you might still be able to install nested ESXi or other hypervisors but you will not be able to run nested 64-bit virtual machines. I would also recommend taking a look at your system BIOS to ensure things like Intel-VT/EPT and AMD-V/RVI are enabled and sometimes it might just be as simple as a BIOS upgrade (you can always confirm by contacting the hardware vendor if you have further questions).

For proper networking connectivity, also ensure that either your standard vSwitch or Distributed Virtual Switch has both promiscuous mode and forged transmit enabled either globally on the portgroup or distributed portgroup your nested ESXi hosts are connected to.

Additional Resources: 

Nested ESXi 5.1 Supports VMXNET3 Network Adapter Type

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I noticed something interesting while extracting the contents of ESXi 5.1 ISO for some kickstart configurations ....

Do you see it? It's a VMXNET3 driver for the VMkernel! I also confirmed by running the following ESXCLI command querying for the VMkernel module "vmxnet3":

# esxcli system module get -m vmxnet3
Module: vmxnet3
Module File: /usr/lib/vmware/vmkmod/vmxnet3
License: GPL
Version: Version 1.1.32.0, Build: 799733, Interface: 9.2 Built on: Aug  1 2012
Signed Status:
Signature Issuer:
Signature Digest:
Signature FingerPrint:
Provided Namespaces:
Required Namespaces: [email protected], [email protected]_1_0_0

***Disclaimer***: This is for educational purposes only, this is not officially supported by VMware. Use at your own risk. There is also a mention of this in the vSphere 5.1 release notes that VMs running on nested ESXi hosts using VMXNET3 driver could potentially crash. Again, not supported user at your own risk.

Next I decided to create a Nested ESXi 5.1 VM, but instead of selecting the e1000 driver which was the only network adapter type that would function for running a nested ESXi host, I choose the VMXNET3 adapter and to my surprise ESXi's networking stack was fully functional.

You can see from the above screenshot, I have a two VMXNET3 network adapters for my nested ESXi 5.1 VM. Here are two additional screenshot of the physical adapters as seen by nested ESXi 5.1 host and you can see that it shows up as VMware Inc. VMXNET3

I have not tried any performance tests, so not sure if there are going to be any significant benefits but pretty cool nonetheless!