When entering Coherence mode in Linux virtual machines, you might be asked to disable display visual (3D) effects in the virtual machine to ensure its proper performance.
IMPORTANT: Gnome 3 desktop implementations vary from one Linux distributive to another. Therefore it's not always possible to enable Coherence view mode when running Linux VM. Currently one should consider installing KDE or MATE desktop managers
The resolution is to disable Desktop Visual Effects in Linux VMs or install KDE packages in those guest OSes which don't allow disabling Desktop Visual Effects (e.g Fedora 23 or later, CentOs, etc):
Ubuntu Linux (Unity desktop environment)
Fedora and CentOs Linux (Gnome 3 desktop environment)
Linux Mint (Chinnamon, MATE and XFCE desktop environments)
OpenSuse, Linux Mint (KDE based)