Comment 2 for bug 1843151

Finding a minimal case did shed some light on this.

Using QEMU's native graphics window, this works fine:

$ /usr/bin/qemu-system-x86_64 \
   -m 1G \
   -blockdev raw,node-name=install_iso,read-only=on,file.driver=file,file.filename=/mnt/losable/ISOs/archlinux-2019.09.01-x86_64.iso \
   -device ide-cd,drive=install_iso,bus=ide.0,bootindex=0

But, introducing spice reproduces the problem:

$ /usr/bin/qemu-system-x86_64 \
   -m 1G \
   -blockdev raw,node-name=install_iso,read-only=on,file.driver=file,file.filename=/mnt/losable/ISOs/archlinux-2019.09.01-x86_64.iso \
   -spice unix,addr=/tmp/spice.qxl.sock,disable-ticketing \
   -device ide-cd,drive=install_iso,bus=ide.0,bootindex=0 \
   -vga qxl

$ remote-viewer "spice+unix:///tmp/spice.qxl.sock"

I've been running remote-viewer (from virt-viewer package) since around March 13, version 8.0 since then. It's only when upgrading QEMU from 4.0.0 to 4.1.0 that introduces the problem.

Running remote-viewer this way also shows that it outputs these, right when KMS changes resolution:

(remote-viewer:15090): GLib-GObject-WARNING **: 23:56:03.914: value "64" of type 'gint' is invalid or out of range for property 'desktop-width' of type 'gint'

(remote-viewer:15090): GLib-GObject-WARNING **: 23:56:03.915: value "64" of type 'gint' is invalid or out of range for property 'desktop-height' of type 'gint'

When downgrading to QEMU 4.0.0, remote-viewer STILL outputs these lines regarding desktop-width and height, when KMS changes resolution.

In case it helps, below are spice-debug logs from remote-viewer. I've included the whole log, but also added a bunch of spacing and a header showing the second worth of output correlating with the KMS resolution change.

QEMU 4.0.0 without the bug: http://ix.io/1USn

QEMU 4.1.0 with the bug: http://ix.io/1USo

So, it's always possible the fix might need to be in remote-viewer, but at minimum, the case it would need to handle properly wasn't being given to it until QEMU 4.1.0.