I have also experienced the same behaviour on Dell XPS 9550 (Skylake). Once I downgraded to previous version of this package, the vm's would start again. What happens is in virtual manager that as soon as I start a VM, it just stops right there - you cannot even see BIOS posting. The error in my logs was the same as noted by Christian. No restart of PC or libvirtd didn't change the behaviour, so it must be something in the package that causes this.
Aljaz
