[Bug 1898490] Re: gtk with virtio and opengl black screen

[Paul Donohue]

The problem is that Xfwm's built-in compositor and virgl don't play nice
together.

Work-around: Boot the VM with virgl=off (on the video device) or gl=off
(on the display), run xfwm4-tweaks-settings in the VM, select the
"Compositor" tab, and uncheck "Enable display compositing".  Then shut
down the VM and re-enable virgl.

picom works with Xfwm and doesn't seem to have the same issues, so if
you want a compositor, install/use picom in the VM instead of using
Xfwm's built-in compositor: https://wiki.archlinux.org/index.php/Picom

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https://bugs.launchpad.net/bugs/1898490

Title:
  gtk with virtio and opengl black screen

Status in QEMU:
  New

Bug description:
  qemu-system-x86_64 -name manjaro -enable-kvm -cpu host -smp
  cores=4,threads=1 -M q35 -m 8G -cdrom /mnt/Storage/ISO/manjaro-
  gnome-20.0.3-minimal-200606-linux56.iso -machine type=pc,accel=kvm
  -vga virtio -display sdl,gl=on Boots properly and has working 3d
  acceleration with virgl.

  Running qemu-system-x86_64 -name manjaro -enable-kvm -cpu host -smp
  cores=4,threads=1 -M q35 -m 8G -cdrom /mnt/Storage/ISO/manjaro-
  gnome-20.0.3-minimal-200606-linux56.iso -machine type=pc,accel=kvm
  -vga virtio -display gtk,gl=on however, (difference being gtk instead
  of sdl), the screen is black, and the vm still starts.

  System Specs
  Gentoo Linux 64bit
  Gentoo-Sources 5.8.13 Kernel
  Qemu 5.10.0-r1 compiled with USE="aio bzip2 caps curl fdt filecaps gtk jpeg 
ncurses nls opengl oss pin-upstream-blobs png pulseaudio sdl seccomp slirp 
spice usb usbredir vhost-net virgl vnc xattr xkb" PYTHON_TARGETS="python3_7" 
QEMU_SOFTMMU_TARGETS="x86_64" QEMU_USER_TARGETS="x86_64"

  Ryzen 7 2700x
  Nvidia 1070ti GPU

  I can confirm the same issue when using libvirt with opengl.

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