As Wide As The Day Is Long

An LG UltraWide monitor supports a 32:9 aspect ratio, up to 5120 x 1440.

Windows running under Libvirt on Linux with the VirtIO graphics driver does not have a hi-res 32:9 mode, so at fullscreen the picture is either stretched wide or has large left and right margins.

Ideally we'd like 3840 x 1080, as full resolution may be excessive for a VM, but this is still quite hi-res.

The desired mode can be hacked into kvm-guest-drivers-windows/viogpu/common/edid.cpp, just over-writing the references to 3840 x 2160

static VIC_MODE gpu_vic_mode_table[] =
{
    {1, {640, 480}},
    {2, {720, 480}},
    ...
    {93, {3840, 2160}},
    {94, {3840, 2160}},
    ...
    {127, {5120, 2160} },
}

Building is quite complicated, requiring the Enterprise Windows Driver Development Kit among other things.

Once the driver is built it can be signed with a Test certificate.

To use the driver, first Secure Boot has to be turned off.

The firmware OVMF_CODE_4M.secboot.fd can no longer be used in Libvirt and the secure-boot and enrolled-keys features should be disabled.

/etc/libvirt/qemu/win11.xml

  <os firmware="efi">
    <type arch="x86_64" machine="pc-q35-8.2">hvm</type>
    <firmware>
      <feature enabled="no" name="enrolled-keys"/>
      <feature enabled="no" name="secure-boot"/>
    </firmware>
    <loader readonly="yes" type="pflash">/usr/share/OVMF/OVMF_CODE_4M.fd</loader>
    <nvram template="/usr/share/OVMF/OVMF_VARS_4M.fd">/var/lib/libvirt/qemu/nvram/win11_VARS.fd</nvram>
    <boot dev="hd"/>
  </os>

The Windows 11 VM may die at this point, but Startup Repair can hopefully fix it.

Then test signing has to be allowed in Windows.

bcdedit /set testsigning on

Windows displays a water-mark, this can be hidden with Universal Watermark Disabler.

This file was updated at 2025-03-01 19:15:47