I ran into this error in the test lab today and figured I would document the cause. When you create a QEMU/KVM virtual machine using the command line virt-install or the graphical virtual machine manager you get an error similar to the following
Error starting domain: internal error: process exited while connecting to monitor: ioctl(KVM_CREATE_VM) failed: 16 Device or resource busy failed to initialize KVM: Device or resource busy
This is caused by the virtualization technology for your CPU (Intel VT-x or AMD-V) being locked by another hypervisor, in our case it was VirtualBox. If we had VirtualBox open we could build and start our QEMU/KVM machines just fine however as soon as we started one of our VirtualBox machines and tried to build or start a QEMU/KVM machine we would get the error.
Interestingly if you had your QEMU/KVM machines running first and then tried to start a VirtualBox machine, the error message from VirtualBox tells you straight away what the error is, something along the lines of “Intel VT-x is in use by another hypervisor”.
Probably not something many people will encounter but it might help somebody.