Emulated VGA in HVMs advertises resolutions that aren't actually supported by the VGA adapter

[ArrayBolt3]

How to file a helpful issue

Qubes OS release

R4.3

Brief summary

Some of the resolutions advertised to HVMs by the VGA emulation aren't supported by the VGA emulation itself. One of those resolutions is 1366x768, which if actually set will result in a badly distorted flashy mess. This happens in arbitrary Linux distributions regardless of display server (X or Wayland) to my awareness; I can reproduce the issue on openSUSE Tumbleweed (both XFCE and GNOME) and Kicksecure 18. All show 1366x768 as available; Kicksecure and openSUSE Tumbleweed XFCE show distortion when set to these resolutions, while openSUSE Tumbleweed GNOME ends up set to 1360x768 when 1366x768 is requested.

Steps to reproduce

1. Download an OpenSUSE live image from https://get.opensuse.org/tumbleweed/?type=desktop#download, which image doesn't matter.
2. Create a new HVM, set its memory to 4000/4000 MB, and disable memory balancing.
3. Boot the HVM from the downloaded ISO.
4. Look at the display resolution settings. 1366x768 will be advertised.
5. Set the resolution to 1366x768.

Expected behavior

1366x768 either should not be advertised, or should work properly.

Actual behavior

1366x768 is recognized, and when set it results in either a badly distorted, unusable display, or a slightly smaller display than expected.

Additional information

This issue does not occur with QEMU 10.1.2 build from source on Kubuntu 24.04 (the 1366x768 display mode isn't advertised at all). Thus if this is a QEMU bug, it's probably fixed upstream already.

[jmynes]

This also happens on Windows qubes