I setup a Linux VM passing through a NVIDIA Geforce 770.
With the open source nouveau driver, it works great. With the proprietary NVIDIA driver, the fan speed goes to max as soon as Xorg initializes. I've tried both Ubuntu and Arch linux with the same results. Windows 10 works fine though (although obviously that's a different driver.)
nvidia-settings always reports that the fan RPM is 0. The same is true with lm_sensors. So, I think this might be the cause, the driver sees the fan speed is 0, so it ramps up the fan speed, but it still reads 0, so it ramps it up even further.
I'm forced to use the nouveau driver for now to save from going deaf in one ear, but it would be nice to use the nvidia driver for a few games.