Qemu: dual display with VGA passthrough AND virtual display device?

Question

I'm evaluating a move from VirtualBox to Qemu / Libvirt, largely because I want to play with VGA passthrough. I have a basic system running now.

I want my Windows VM to have dual displays, with both the passed-through NVidia display AND a virtual display. (Ultimately, I'd like to find a way to clone the hardware display to the virtual display, perhaps with third-party software.)

When I keep the QXL virtual display in a VM that has the passthrough GPU, it reports error Windows has stopped this device because it has reported problems. (Code 43). Is this worth trying to troubleshoot?

TLDR: Can I run a VM with a virtual display AND passthrough VGA? Can I mirror one to the other?

Answer 1

My question had some poor assumptions.

• The code 43 is NVidia's way of preventing you from emulating CUDA performance with commodity hardware.
• I haven't yet found a way to run QXL/Spice and a passed-through GPU, but xfreerdp has done a pretty good job of meeting my needs.

EDIT:

Looking-glass doesn't precisely answer the question, but it solves the underlying problem nearly perfectly -- providing GPU-accelerated VM graphics on the host desktop. In alpha as of Dec 2017, but appears stable enough for everyday use on a single display.