Change number of CPUs in VirtualBox is disabled

I'm using virtualbox with Kali and it's working fine, however I currently only have it using 1 cpu and I'd like to add more.

However when I go to Settings → System → Processor the fields are greyed out and I can't change number of processors (this happens even when kali isn't running). Any help is appreciated

Solution 1:

You can find the workaround here: How do I enable multiple cores in my virtual enviroment?.

To enable more than 1 CPU in your VM the following settings are needed in addition:

• 64-bit virtual guest hardware in General settings tab (for 64-bit guests)

• Enable I/O APIC in the Motherboard settings tab

• Enable hardware virtualization (VT-x/AMD-V) in the Acceleration tab

Note that if your run your VM on all cores available you may experience a better host performance when assigning an execution cap to the CPU.

You won't be able to edit the CPU count while the VM is running or has a saved state, so make sure that it is in the powered off state.