/dev/kvm permission denied.
After updating Ubuntu to 18.04 version you should install qemu-kvm
sudo apt install qemu-kvm
Check the owner of /dev/kvm
ls -al /dev/kvm
It should return User root, group kvm.
To check which users are in kvm group:
grep kvm /etc/group
It should return something like that:
There was not a value after the last colon after I've updated my OS. This means that no users are present in kvm Group.
To add your user to kvm Group use the command:
sudo adduser $USER kvm
Check if the user was added:
grep kvm /etc/group.
If after those actions you still see an error message - try to re-login to make user permission refreshed.