006: The Linux GPU desktop runs Xorg with NVIDIA's driver, streamed by x0vncserver

Status: accepted, 30 September 2026. Research: the GPU in a desktop box. Partly superseded by 021: the screen resizes with xrandr --fb, so the backend resizes it for the viewer. Extended by 020: a GPU desktop that fell back to the CPU is retried on another GPU; and by 048: a Wayland desktop on the GPU needs a host setting that this decision’s Xorg path does not.

Context

The desktop box exists for GPU-rendered apps: Chrome with WebGL and WebGPU, and native apps such as GPUI apps on Vulkan. In an unprivileged container with no monitor, measured on an NVIDIA GPU:

Display server	Result
Xtigervnc	CPU only; Vulkan cannot present on NVIDIA
Xtigervnc with VirtualGL	OpenGL on the GPU, no Vulkan
Xorg with NVIDIA’s driver on a virtual screen	OpenGL, Vulkan, Chrome and GPUI all on the GPU

Selkies’ patched Xvfb would keep the screen on the GPU and allow resizing and more desktops per GPU. It needs the host’s nvidia_drm module loaded with modeset=Y, and changing that means reloading the module or rebooting the host.

Decision

• The desktop template runs Xorg with NVIDIA’s driver on a virtual screen, served by x0vncserver from upstream TigerVNC 1.16.2. Ubuntu 24.04’s 1.13.1 lacks clipboard support in x0vncserver and the fix for CVE-2026-34352.
• Each desktop sees one GPU. With two GPUs visible, Vulkan could not present.
• Without a usable GPU (no device, or a driver mismatch), the box falls back to Xtigervnc on the CPU and reports why.
• The patched Xvfb is parked until the operator sets modeset=Y on the host. Then the experiment in the research note decides whether to switch.

Consequences

• The desktop cannot resize to the panel; it keeps the size it started with.
• x0vncserver copies each update from GPU memory on the CPU.
• Each desktop uses 40 to 47 MiB of GPU memory for Xorg, and Chrome’s GPU process 100 to 300 MB more. The backend reports GPU desktops per GPU, and a setting caps them so other workloads on the host keep their memory.
• The box reports whether it came up on the GPU or the CPU. The panel shows it and the agent can read it.