qemu 8.1.0 breaks gvt-g + qemu-ui-gtk w gl=on (black screen, qemu: eglCreateImageKHR failed)

Host environment

• Operating system: Manjaro latest, Artix latest
• OS/kernel version: Linux a-PC 6.4.14-1-MANJARO
• Architecture: x86_64
• CPU: i5-5300u
• GPU driver: mesa 23.1.6-3 (i915)
• QEMU flavor: qemu-system-x86_64
• QEMU version: QEMU emulator version 8.1.0
• QEMU command line:

  ./qemu-system-x86_64 -M q35 -m 4096 -enable-kvm -hda win10.qcow2 \
      -drive if=pflash,format=raw,readonly=on,file=/usr/share/edk2-ovmf/x64/OVMF_CODE.fd \
      -drive if=pflash,format=raw,file=/home/user/VM/win10/OVMF_VARS.fd \
      -display gtk,gl=on \
      -video none
      -device vfio-pci,sysfsdev=/sys/bus/mdev/devices/$GVT_GUID,x-igd-opregion=on,romfile=/home/user/VM/i915ovmf.rom,display=on,ramfb=on,driver=vfio-pci-nohotplug 

Emulated/Virtualized environment

• Operating system: Windows 10 21H1
• Architecture: x86_64

Description of problem

As of 8.1.0, qemu-ui-gtk renders a black window with the error qemu: eglCreateImageKHR failed repeatedly appearing in the command line.

experiments

• fresh artix-runit-xfce install, no luck
• gl=es, no luck (gl=off is impossible w DMA_BUF)
• video qxl + gtk with gl=on -> works fine
• glxgears runs fine, so does 0ad, so do the openGL ES angle demos (they all use gles + egl)
• source build instead of versioned repo package, no luck
• change q35 to 8.0, no luck
• the mother of all downgrades: qemu 8.1.0 to 8.0.4 -> works fine again like it used to!!

Steps to reproduce

1. enable kernel modules, set parameters etc.
2. create vgpu echo "$GVT_GUID" > "/sys/devices/pci0000:00/0000:00:02.0/mdev_supported_types/i915-GVTg_V4_2/create"
3. launch VM
4. wait

Instructions (a small part of which I wrote by trial and error) for the setup are on the Arch Wiki.

observed results

OVMF is displayed correctly through ramfb=on and EFI states it is booting Windows from the HDD.
Sometimes, Windows boot animation is displayed below Tiano Core logo when "configuring devices".
Then qemu-ui-gtk resizes to the resolution set in Windows and displays a black guest screen, repeatedly printing qemu: eglCreateImageKHR failed to the terminal, with varying speed, likely on guest screen refreshes.
After 1-2 minutes qemu CPU usage goes down to usual "Windows is idling" levels (fairly high due to 60fps guest display redraws but I guess that can't be avoided).

Additional information

Windows is installed directly to a second SSD, I dual-boot it.
I've been using this exact VM, from libvirt, for almost two years.
relevant sections:

    <hostdev mode="subsystem" type="mdev" managed="no" model="vfio-pci" display="off">
      <source>
        <address uuid="$GVT_GUID"/>
      </source>
    </hostdev>
  </devices>
  <qemu:commandline>
    <qemu:arg value="-display"/>
    <qemu:arg value="gtk,gl=on,zoom-to-fit=off"/>
    <qemu:env name="DISPLAY" value=":0.0"/>
  </qemu:commandline>
  <qemu:override>
    <qemu:device alias="hostdev0">
      <qemu:frontend>
        <qemu:property name="x-igd-opregion" type="bool" value="true"/>
        <qemu:property name="driver" type="string" value="vfio-pci-nohotplug"/>
        <qemu:property name="ramfb" type="bool" value="true"/>
        <qemu:property name="display" type="string" value="on"/>
        <qemu:property name="romfile" type="string" value="/home/user/VM/vbios_gvt_uefi.rom"/>
      </qemu:frontend>
    </qemu:device>
  </qemu:override>

The patched vBIOS necessary to use DMA-BUF with OVMF is linked there too, but its successors doesn't work either.

how to downgrade qemu to 8.0.4 (assuming arch-based)

sudo pacman -S qemu-desktop
sudo pacman -Rdd qemu-audio-pipewire
sudo downgrade qemu-audio-alsa qemu-audio-dbus qemu-audio-jack qemu-audio-oss qemu-audio-pa qemu-audio-sdl qemu-audio-spice qemu-base qemu-block-curl qemu-block-dmg qemu-block-nfs qemu-block-ssh qemu-chardev-spice qemu-common qemu-hw-display-qxl qemu-hw-display-virtio-gpu qemu-hw-display-virtio-gpu-gl qemu-hw-display-virtio-gpu-pci qemu-hw-display-virtio-gpu-pci-gl qemu-hw-display-virtio-vga qemu-hw-display-virtio-vga-gl qemu-hw-usb-host qemu-hw-usb-redirect qemu-hw-usb-smartcard qemu-system-x86 qemu-system-x86-firmware qemu-ui-curses qemu-ui-dbus qemu-ui-egl-headless qemu-ui-gtk qemu-ui-opengl qemu-ui-sdl qemu-ui-spice-app qemu-ui-spice-core qemu-vhost-user-gpu qemu-desktop qemu-img

Or pacman -Rdd all of the above and then pacman -U *.tar.zst from a dir containing the 8.0.4 packages.

Good thing my SSD is a mess and these old packages are still present!
If anyone wants them I can upload them.

Then the VM works just fine, full gvt-g + qemu gtk-opengl performance.

reason for wanting GVT-G + gtk w openGL

On weak CPUs like my 5300u, this combo gives almost-native performance and full 3d accel!!