1 – change type emulation to SOFTWARE (device settings),
2 – if your environment usage dedicated VGA or integrated VGA with acceleration try enable another drive that not has default drive, for example, GTX 900 series usage noveau driver, try proprietary driver and enjoy :).
Ex, on Mint 19.x -> Menu -> Administration -> Driver Manager -> choose Nvidia instead of noveau (xorg based) and enjoy!
3 – Add user to KVM:
sudo adduser yourlogin kvm
OU root group (not secure)
KVM is GROUP on this syntax!
This solution working fine with Ubuntu/Mint/Ubuntu based!