xserver error fix after gentoo system upgrade

When use NVIDIA Graphic card, drivers for graphic card should not be upgraded. 

It would be better download driver through NVIDIA homepage directly and install after system upgrade. 

Xserver and Xorg-drivers must match with graphic card version. maybe downgrade?

Reinstall drivers for input devices (keyboard, mouse..) -> xf86-input-libinput

Virtualbox reinstall through virtualbox homepage. 

maybe it can done with emerge. but virtualbox version and qt version must match, so it can be messy.