Win11 - Transparency/blur broken on VirtIO GPU drivers even when using 3D acceleration

[PlatinumLucario]

Describe the bug
This seems to only occur on certain AMD graphics cards, such as AMD Radeon RX 6900 XT.

The virtio drivers install successfully, and appear to be working in Device Manager, but all the 3D acceleration features such as transparency, blur and rounded corners effects are not working at all.

Furthermore, it can only render graphics up to OpenGL 1.1, which shouldn't be the case, it should be at a much higher OpenGL version.

To Reproduce
Steps to reproduce the behaviour:

1. Install Windows 11.
2. Install virtio/kvm guest drivers

or

1. Before installing Windows 11, install the virtio drivers manually (except for the graphics driver, which can't be installed without causing the screen to go blank and unusable).
2. Install Windows 11.
3. Install virtio graphics driver.

Expected behavior
Installing the virtio graphics drivers should make all the transparency, blur and rounded corners work.

Screenshots

Host:

• Disto: Fedora Workstation 41
• Kernel version: 6.13.5-200.fc41.x86_64
• QEMU version: qemu-2:9.1.3-1.fc41.x86_64
• QEMU command line
• libvirt version: libvirt-10.6.0-6.fc41.x86_64
• libvirt XML file:
  /etc/libvirt/qemu/win11.xml

<!--
WARNING: THIS IS AN AUTO-GENERATED FILE. CHANGES TO IT ARE LIKELY TO BE
OVERWRITTEN AND LOST. Changes to this xml configuration should be made using:
  virsh edit win11
or other application using the libvirt API.
-->

<domain type='kvm'>
  <name>win11</name>
  <uuid>c9bbeda9-0500-4f2e-9fcf-0af0c8155264</uuid>
  <metadata>
    <libosinfo:libosinfo xmlns:libosinfo="http://libosinfo.org/xmlns/libvirt/domain/1.0">
      <libosinfo:os id="http://microsoft.com/win/11"/>
    </libosinfo:libosinfo>
  </metadata>
  <memory unit='KiB'>33554432</memory>
  <currentMemory unit='KiB'>33554432</currentMemory>
  <vcpu placement='static'>32</vcpu>
  <os firmware='efi'>
    <type arch='x86_64' machine='pc-q35-9.1'>hvm</type>
    <firmware>
      <feature enabled='yes' name='enrolled-keys'/>
      <feature enabled='yes' name='secure-boot'/>
    </firmware>
    <loader readonly='yes' secure='yes' type='pflash'>/usr/share/edk2/ovmf/OVMF_CODE.secboot.fd</loader>
    <nvram template='/usr/share/edk2/ovmf/OVMF_VARS.secboot.fd'>/var/lib/libvirt/qemu/nvram/win11_VARS.fd</nvram>
    <boot dev='hd'/>
  </os>
  <features>
    <acpi/>
    <apic/>
    <hyperv mode='custom'>
      <relaxed state='on'/>
      <vapic state='on'/>
      <spinlocks state='on' retries='8191'/>
      <vpindex state='on'/>
      <runtime state='on'/>
      <synic state='on'/>
      <stimer state='on'/>
      <frequencies state='on'/>
      <tlbflush state='on'/>
      <ipi state='on'/>
      <avic state='on'/>
    </hyperv>
    <vmport state='off'/>
    <smm state='on'/>
  </features>
  <cpu mode='host-passthrough' check='none' migratable='on'>
    <topology sockets='1' dies='1' clusters='1' cores='4' threads='8'/>
  </cpu>
  <clock offset='localtime'>
    <timer name='rtc' tickpolicy='catchup'/>
    <timer name='pit' tickpolicy='delay'/>
    <timer name='hpet' present='no'/>
    <timer name='hypervclock' present='yes'/>
  </clock>
  <on_poweroff>destroy</on_poweroff>
  <on_reboot>restart</on_reboot>
  <on_crash>destroy</on_crash>
  <pm>
    <suspend-to-mem enabled='no'/>
    <suspend-to-disk enabled='no'/>
  </pm>
  <devices>
    <emulator>/usr/bin/qemu-system-x86_64</emulator>
    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2'/>
      <source file='/run/media/platinumlucario/Storage/VMs/win11/win11.qcow2'/>
      <target dev='vda' bus='virtio'/>
      <address type='pci' domain='0x0000' bus='0x04' slot='0x00' function='0x0'/>
    </disk>
    <disk type='file' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <source file='/run/media/platinumlucario/Storage/ISOs/Win11_24H2_English_x64.iso'/>
      <target dev='sdb' bus='sata'/>
      <readonly/>
      <address type='drive' controller='0' bus='0' target='0' unit='1'/>
    </disk>
    <disk type='file' device='cdrom'>
      <driver name='qemu' type='raw'/>
      <source file='/run/media/platinumlucario/Storage/ISOs/virtio-win-0.1.266.iso'/>
      <target dev='sdc' bus='sata'/>
      <readonly/>
      <address type='drive' controller='0' bus='0' target='0' unit='2'/>
    </disk>
    <controller type='usb' index='0' model='qemu-xhci' ports='15'>
      <address type='pci' domain='0x0000' bus='0x02' slot='0x00' function='0x0'/>
    </controller>
    <controller type='pci' index='0' model='pcie-root'/>
    <controller type='pci' index='1' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='1' port='0x10'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x0' multifunction='on'/>
    </controller>
    <controller type='pci' index='2' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='2' port='0x11'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x1'/>
    </controller>
    <controller type='pci' index='3' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='3' port='0x12'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x2'/>
    </controller>
    <controller type='pci' index='4' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='4' port='0x13'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x3'/>
    </controller>
    <controller type='pci' index='5' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='5' port='0x14'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x4'/>
    </controller>
    <controller type='pci' index='6' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='6' port='0x15'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x5'/>
    </controller>
    <controller type='pci' index='7' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='7' port='0x16'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x6'/>
    </controller>
    <controller type='pci' index='8' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='8' port='0x17'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x02' function='0x7'/>
    </controller>
    <controller type='pci' index='9' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='9' port='0x18'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x0' multifunction='on'/>
    </controller>
    <controller type='pci' index='10' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='10' port='0x19'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x1'/>
    </controller>
    <controller type='pci' index='11' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='11' port='0x1a'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x2'/>
    </controller>
    <controller type='pci' index='12' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='12' port='0x1b'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x3'/>
    </controller>
    <controller type='pci' index='13' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='13' port='0x1c'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x4'/>
    </controller>
    <controller type='pci' index='14' model='pcie-root-port'>
      <model name='pcie-root-port'/>
      <target chassis='14' port='0x1d'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03' function='0x5'/>
    </controller>
    <controller type='sata' index='0'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x1f' function='0x2'/>
    </controller>
    <controller type='virtio-serial' index='0'>
      <address type='pci' domain='0x0000' bus='0x03' slot='0x00' function='0x0'/>
    </controller>
    <interface type='network'>
      <mac address='52:54:00:33:19:c5'/>
      <source network='default'/>
      <model type='e1000e'/>
      <address type='pci' domain='0x0000' bus='0x01' slot='0x00' function='0x0'/>
    </interface>
    <serial type='pty'>
      <target type='isa-serial' port='0'>
        <model name='isa-serial'/>
      </target>
    </serial>
    <console type='pty'>
      <target type='serial' port='0'/>
    </console>
    <channel type='spicevmc'>
      <target type='virtio' name='com.redhat.spice.0'/>
      <address type='virtio-serial' controller='0' bus='0' port='1'/>
    </channel>
    <input type='tablet' bus='usb'>
      <address type='usb' bus='0' port='1'/>
    </input>
    <input type='mouse' bus='ps2'/>
    <input type='keyboard' bus='ps2'/>
    <tpm model='tpm-crb'>
      <backend type='emulator' version='2.0'/>
    </tpm>
    <graphics type='spice'>
      <listen type='none'/>
      <image compression='off'/>
      <gl enable='yes' rendernode='/dev/dri/by-path/pci-0000:03:00.0-render'/>
    </graphics>
    <sound model='ich9'>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x1b' function='0x0'/>
    </sound>
    <audio id='1' type='spice'/>
    <video>
      <model type='virtio' heads='1' primary='yes'>
        <acceleration accel3d='yes'/>
      </model>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0'/>
    </video>
    <redirdev bus='usb' type='spicevmc'>
      <address type='usb' bus='0' port='2'/>
    </redirdev>
    <redirdev bus='usb' type='spicevmc'>
      <address type='usb' bus='0' port='3'/>
    </redirdev>
    <watchdog model='itco' action='reset'/>
    <memballoon model='virtio'>
      <address type='pci' domain='0x0000' bus='0x05' slot='0x00' function='0x0'/>
    </memballoon>
  </devices>
</domain>

VM:

• Windows version: Windows 11 Pro Version 24H2 (OS Build 26100.3194, Windows Feature Experience Pack 1000.26100.48.0) Microsoft Windows [Version 10.0.26100.3194]
• Which driver has a problem: Red Hat VirtIO GPU DOD controller
• Driver version or commit hash that was used to build the driver: 100.100.104.26600

Additional context
You'd really expect that a modern graphics card would work without any issues on a VirtIO GPU driver, but nope it doesn't. And just to clarify, this was tested on virt-manager, which uses qemu and kvm anyways.

If there's any workaround to this issue, please let me know. Thanks!

[YanVugenfirer]

Unfortunately virtio-gpu on windows is a display only driver and it doesn’t support 3D acceleration

[PlatinumLucario]

Ah I see, that explains it.

Is there a better driver to use for 3D acceleration on Windows 11 guests? Or is passthrough the only answer?

[YanVugenfirer]

There is an experimental pull request with 3D support: #943
Passthrough is the stable answer for now.