#Starting with Ubuntu 18.04 and Linux Mint Tara you need to install qemu-kvm
sudo apt install qemu-kvm

#Check the ownership of /dev/kvm
ls -al /dev/kvm

#Check which users are in the kvm group
grep kvm /etc/group

#Output from the above command

#kvm:x:some_number:
#If there is nothing rightwards of the final :, there are no users in the kvm group.

#To add the current user to the kvm group
sudo adduser $USER kvm

#which adds the user to the group, and check once again with grep kvm /etc/group.

#A restart may be required for the permissions to take effect.