1. Load kvm_amd kernel module
2. Start kvm VM with kvm command
3. Stop kvm VM
4. Load VirtualBox vboxdrv kernel module
5. Start VirtualBox GUI, start VM, exit VM, close VirtualBox GUI
6. Start kvm VM with kvm -vnc ... command
All steps up to step 5 work.
In Step 6, kvm starts and keeps running, I can connect to VNC, but I only get a black screen. No error message.
In step 6, kvm command immediately exits, with an error message:
"Another virtual machine manager like VirtualBox, Xen or VMWare is running at the moment. Check 'lsmod' that no virtual machine manager modules other than 'kvm*' are loaded."