I have a libvirt/KVM with QEMU running a Windows 7 guest using the Spice/QXL video emulator.

How do I set a graphics mode not listed by default in the Windows screen resolution settings? For example, a mode like 2048x900 would be nice. The guest has a 21:9 screen and its very low height limits the use of hi-res 4:3 modes available in Windows.

I tried installing the Windows guest tools "guest agent" by Red Hat but they won't install. Therefore I am hoping for a solution that works by instructing spice what to emulate.

I read that using a Linux guest one can do these things directly from the guest by adding a new mode line with xrandr but I do not know how to do these things with the confusing graphical settings interface in Windows.

Ideally, of course, the screen resolution of the guest would change with the guest window size but I know that this would require some sort of guest tools that I do not have - or just won't install.

  • Normally once Spice video drivers are installed you can change the guest resolution by simply resizing the guest window. What is the windows version that you have in the guest? What do you mean exactly "they won't install"? Did the install fail or run so silent that you have no clue whether they're installed or not? Did you also try QXL Spice video drivers alone? I never had any troubles with spice video drivers but I must confess my guests were (and still are) limited to Windows XP.
    – user86969
    Dec 6, 2017 at 13:23
  • Thanks. The tools won't install means, when I call the install file with admin privs the process fails without error message. Afterwards no drivers are installed. No firewall of any sort hinders installation. I can easily install other programs. As I wrote, the Windows version is 7 - a 64-bit Enterprise variant to be precise.
    – Ned64
    Dec 6, 2017 at 22:43
  • Hmmm... there ain't no file to "execute" or "call", strictly speaking. The driver directory contains a CAT file, an INF file, a SYS file and a DLL file. All you have to do is (maybe forcibly) update the corresponding (unknown) driver with the Qxl INF file and you're all set. That's what I can see from the virtual ISO image that contains all the drivers on my virtual XP machine. Normally you should be prompted with a request for a driver file when you boot your virtual machine. From there you should be allowed to pick the INF file from the QXL\W7\AMD64 directory.
    – user86969
    Dec 7, 2017 at 0:02

1 Answer 1


For Windows 10 this worked fine with my 2560x1080 display. I've got to imagine it would work fine for Windows 7 just as long as the guest extensions remain compatible with it.

  1. First I installed the Spice guest extensions on the Windows 10 guest (and rebooted the guest, though may not be needed).
  2. Then I enabled "Auto resize VM with window" from Virtual Machine Manager.
  3. Finally I resized the guest by dragging a corner to test, and then switched the guest to full screen and the guest filled my entire 2560x1080 display!

Auto resize VM with window

  • Thanks, voting it up because it is plausible that this would work. Since I could not install the Spice guest extension and the problem arose 3 years ago I cannot test it now as I could not do then.
    – Ned64
    Jun 20, 2020 at 20:56
  • 1
    The only missing info here is that the vm must be using QXL driver for video. I was using virtio, so the spice extension install was not producing effects. Jan 8, 2021 at 17:17
  • Is there a way to set a video resolution larger than your native screen size?
    – yeah22
    Feb 4, 2021 at 1:44
  • @yeah22 Yes that should be possible. The driver (QXL) onlz needs to be able to handle it (memory allocation etc.).
    – Ned64
    Jul 17, 2021 at 13:04

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