Virtualbox enable nested vtx/amd-v greyed out

Question

On my Ubuntu 18.04, I\'ve installed VirtualBox 6.0 in order to have nested virtualization. Virtualization is

Answer 1

It turned out it was greyed out for a reason! I have Windows 10 host and I used Docker for some time and uninstalled but it kept Hyper-V technology enabled (Which is incompatible with virtualization).

DO NOT DO ON A SERVER | THIS WILL DISABLE Hyper-V Technology - USE AT YOUR OWN RISK

Open command prompt as admin and run the following then restart your PC

DISM /Online /Disable-Feature:Microsoft-Hyper-V

PowerShell Disable-WindowsOptionalFeature -Online -FeatureName Microsoft-Hyper-V-Hypervisor -All

bcdedit /set hypervisorlaunchtype off

Answer 2

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.