Nested virtualization with Workstation Pro 15.0.2

[TR01]

I want to have nested virtualization and i dont know if there is a special configuration to get this running. Does anyone has some knowledge about that use case? Can anyone help?

My setup looks like this:

• A physical device with Win10 x64 with Workstation Pro 15.0.2 (This version is mandatory) installed
• A VM inside this workstation also with Workstation Pro 15.0.2 (This version is mandatory) installed

Inside this VM i want to create nested VMs. This runs at the first step, but i recognized some performance issues. At the moment i can`t address them.

The Workstation Pro installation shows also a popup/dialog mentioning that running nested vm can result in a "degraded performance".

Does anybody know which configuration has to be made to be able to run this nested VMs? Whats the cause for this degraded performance? Ist there any documentation for it?

Or do I have to buy a special product/license?

Any information could be helpful. Feel free to ask, if you need more information!

[depping]

Some additional info can be found in this KB: VMware Knowledge Base

Note that we call out "degraded performance" as that is typically what you can expect when you are doing nested performance. Yes you can run something like ESXi within Workstation and then run VMs on ESXi, but as you have an operating system running, and Workstation, and ESXi and then a VM, all those layers will result in degraded performance.

[bluefirestorm]

If you look at the vmware.log file of the very top Windows 10 host level VM, you should see sections called "Host VT-x capabilities", "Guest VT-x capabilities", and "Active HV Capabilities". The "Guest VT-x capabilities" only appear if the "Virtualize Intel VT-x/EPT or AMD-V/RVI" is enabled in the VM Processor settings.

You will see that the "Guest VT-x capabilities" VT-x feature set becomes more reduced (more {0} and "no" than {0,1} and yes) compared to the "Host VT-x capabilities". So it will degrade as the nesting goes deeper.

Generally, the newer generation the CPU, the better it will be for virtualisation (and nested virtualisation) as the overhead cost in terms of clock cycles for a VM-EXIT is lower. VM-EXIT is like a hypervisor equivalent of what a process context switch is to a regular OS.

For nested virtualisation, it is better to have at least Haswell or newer generation for Intel CPUs as it has features (e.g. nested paging access/dirty bits, VMCS shadow) that will lessen the occurrence for such VM-EXITs.