[CentOS] Resizing a QEMU guest display

Sat Feb 6 18:26:40 UTC 2021
Bill Gee <bgee at campercaver.net>

Hello everyone -

I think I know the answer, but just in case ...  I want to run it by the experts.

I have a machines running CentOS 7.  "uname -a" returns this:

Linux practice7.billgee.local 3.10.0-1160.15.2.el7.x86_64 #1 SMP Wed Feb 3 15:06:38 UTC 2021 x86_64 x86
_64 x86_64 GNU/Linux

This machine has an nVidia GS8400 and uses the nouveau driver.  Its main job is to be a host for QEMU/KVM virtual machines.  The QEMU packages on the host are:

[bgee at practice7 ~]$ rpm -qa | grep qemu 

One of the guest VMs is Fedora 33.  The guest comes up with a display resolution of 1024x768.  I have not found a way to change it to something higher.  If I go to the Settings - Display item in Fedora, there is a long list of resolutions.  No matter what I choose, the system will switch to that resolution for about 1/2 second and then go back to 1024x768.

This happens when using VNC to connect remotely and also when running on the host computer.  Resizing the guest display window does nothing except make big black borders around the guest display.

The guest video configuration in the virtual machine manager is set for "QXL".  In my searching I found several suggestions to use "virtio" instead.  When I make that change and start the guest, it immediately throws an error:

"This QEMU does not support 'virtio' video device"

I also tried "vmvga" and "cirrus".  The cirrus setting does not resize and also loses coordination of the mouse pointer.  The vmvga setting gives the same message about not being supported in this QEMU.

I verified that the spice-vdagent package is installed on the guest VM.

The virtual machine manager has "Resize guest with window" set to ON.

Just to make life really interesting...  Another guest VM on the same host is running CentOS7.  That machine happily resizes!  It is set for QXL in the virtual machine manager.

I think I am just out of luck.  I found some references which say that CentOS 7 does not have support for virtio displays.  Is that right?  Is there some way to resize the Fedora guest?  I don't care about dynamic sizing by dragging a window border.  If I can choose something and have it stick, I would be happy.


Bill Gee