Oracle VirtualBox Error: VT-x/AMD-V hardware acceleration

I’m running Windows 10 on my home PC, but occasionally use Oracle VirtualBox to run a Linux VM. Recently when I tried to start the VM, I got this error:

 VirtualBox РError

VT-x/AMD-V hardware acceleration is not available on your system. Your 64-bit guest will fail to detect a 64-bit CPU and will not be able to boot.

Screenshot of the error message when Oracle VirtualBox can't detect a 64-bit CPU

Oracle VirtualBox warning that the VM won’t boot

And sure enough, if I press “Continue”, the VM just displays the following when it tries to boot:

This kernel requires an x86-64 CPU, but only detected an i686 CPU.

Unable to boot – please use a kernel appropriate for your CPU.

I didn’t understand why I was getting this – my PC was physically the same as it was last time I’d run it, and I the only thing that was different about the VM was that I’d updated VirtualBox¬† to the latest version, but it couldn’t have been caused by that could it?

I found out that no, it wasn’t.

The one thing that had changed on my PC a few weeks ago was that I’d updated the BIOS. One of the settings in it is called:

BIOS Features –> Intel Virtualization Technology

This was set to “Disabled”. As soon as I changed it to “Enabled”, my VM started working again.