I use Win 8.1 guest and passed through an Intel HD 520, installed successfully latest driver 188.8.131.5248, but I can't enable the graphics card in the display settings. In Win 8.1 setup is default as an extended display, but no matter how I change the settings (change primary display, "show desktop only on Intel HD520", the card doesn't start working. In device manager all looks normal.
Even if I disable the Redhat QXL graphics card in the device manager, the monitor just turns black.
Tried with VNC and SPICE. Tried virt-manager, spicy, remote-viewer. No chance.