Virtualbox enable nested vtx/amd-v greyed out

Execute this:

$ VBoxManage modifyvm vm-name --nested-hw-virt on

For Windows

In Windows, go to VirtualBox installation folders -> type cmd on the bar (it will pop up cmd in that folder) -> type VBoxManage modifyvm YourVirtualBoxName --nested-hw-virt on -> enter.

Now it should been ticked.

From what I understand, this option is only available with AMD CPUs, and cannot be enabled on Intel CPUs. This is a little misleading, since the option clearly states both Intel, and AMD virtualization technologies.

Here is an official confirmation in VirtualBox doc: https://www.virtualbox.org/manual/ch03.html Chapter 3.5.2. Processor Tab

Enable Nested VT-x/AMD-V: Enables nested virtualization, with passthrough of hardware virtualization functions to the guest VM.

This feature is available on host systems that use an AMD CPU. For Intel CPUs, the option is grayed out.

On VirtualBox 6.1.2 that worked (intel i7 2630QM)

(VBoxManage modifyvm lubuntu18 --nested-hw-virt on)