Problem with running Virtualbox Headless and KVM on the same Server

[Sylla]

Hello,

I'm running Virtualbox headless 5.2.22r126460 on a 18.04.1 Ubuntu Server. Now, I'm using GNS3 VM which runs GNS3 Server inside an Ubuntu Server OS (the Guest OS). And because running QEMU based VMs inside Virtualbox is not possible due to the lacking KVM support, I'm trying to let the host OS handle the KVM virtualization. But when I tried to do that I got the following error message: Linux KVM – Error: ioctl(KVM_CREATE_VM) failed: 16 Device or resource busy.

I googled a little and someone presumes that it is because both KVM and Virtualbox are using Intel VT-x/AMD-V hardware virtualization.
Thus my question is:
Is there a way to turn this setting off in Virtualbox Headless? In the gui version this setting will enable itself automatically when being turned off as far as I know.

Thanks.

[socratis]

KVM used to play cooperatively with other virtualization solutions. Not anymore, they pulled a "Microsoft" (Hyper-V) and now they take exclusive control of VT-x leaving the other virtualizers unable to work with recent OSes, which require the presence and availability of VT-x on the host.

Is there a way to turn this setting off in Virtualbox Headless?

It depends on which OS you want to run in the VM. If you want a recent one, chances are no, it won't run. You can try and disable the VT-x in the VM Settings and see if the VM will launch. I'd suggest not starting headless as a first try, just so you'll know what the heck is going on. If it works, you can start experimenting with the headless option, the requirements are the same...

[Sylla]

Then it seems like I'm out of luck. Tried it on my Ubuntu desktop version with the same VM and the setting keeps turning itself on again. I'll look for different solutions then, thank you.