KVM Spice connection to hardware GPU

Question

I have an asymmetric triple-head linux box. It's hosting a Windows 10 VM with GPU passthrough, which I'd like to also have triple-head soft display on the Linux host.

Is there any way to use Spice to expose my NVidia display to virt-viewer?

What I've tried:

• Manually switching the three monitors and having a second keyboard and mouse. This got old very fast.
• Running tightvnc on the guest. Couldn't figure out how to do cross-platform triple-head, and the performance wasn't great anyhow.
• Reinstalled Spice/QXL, and tried to use Actual Multiple Monitors to mirror the GPU display onto the QXL display. Couldn't make it go.

Answer 1

Not technically an answer to my (slightly XY) question, but Xfreerdp supports multi-monitor RDP quite nicely, and windows guests conveniently come with the server already installed. Here's the commandline I needed to connect to a Windows 10 guest.

xfreerdp +nego +sec-rdp +sec-tls +sec-nla /multimon /smart-sizing /v:guestname

Warnings:

• it automatically goes to full-screen, and the only way out is with ctrl-alt-enter (or r-ctrl in v2).
• Obviously, for the host-to-guest connection to work, you have to be using bridged networking
• If your distro doesn't have v2 by default, jump through the hoops to get it. If for nothing else, it's worth it to be able to tap r-ctrl in fullscreen in order to have your mouse and keyboard un-grabbed. Lets you switch to a different workspace with no hassle.
• On Windows 7, you must have Ultimate or Enterprise. Pro just gives you one large desktop spanning all your monitors. Windows 10 appears to support multi-monitor RDP across the board.