Cannot Switch Virtualization Off

[Tim Ellis]

If a VM has virtualization switched on, but the BIOS of the physical machine has virtualization switched off, it is impossible to switch virtualization off for the VM. This is because Virtual Box detects the missing virtualization and grays out the "Acceleration" tab under the System Settings. With this tab missing, it is not possible to deselect hardware virtualization. Further, Virtual Box does not cascade this detection to actually forcing virtualization off for the VM on execution. This causes the VM to crash as it starts up (because the virtualization is physically not available). My suggestion is to always allow the acceleration tab to be accessible. Alternatively, if virtualization is physically not available, just run the VM with the option deselected, even if it is selected under the acceleration tab (in which case, the acceleration tab can remain grayed out if virtualization is off)