Black screen / Xorg segfault on RTX 4070 login (nvidia-open 615.71.09 + modesetting/glamor) — fix included

[Josnork]

NVIDIA Open GPU Kernel Modules Version

615.71.09

Please confirm this issue does not happen with the proprietary driver (of the same version). This issue tracker is only for bugs specific to the open kernel driver.

• I confirm that this does not happen with the proprietary driver package.

Operating System and Version

Arch Linux

Kernel Release

7.2.6-arch2-1

Please confirm you are running a stable release kernel (e.g. not a -rc). We do not accept bug reports for unreleased kernels.

• I am running on a stable kernel release.

Hardware: GPU

NVIDIA GeForce RTX 4070

Describe the bug

Xorg crashes with a segmentation fault immediately after enabling glamor acceleration on an RTX 4070, when using the generic modesetting DDX (i.e. no explicit Driver "nvidia" configured in xorg.conf). This results in Xorg terminating before any display output, breaking any display manager or session relying on X (in my case, an SDDM greeter preceding a Wayland/Hyprland session).

Workaround

Explicitly configuring the nvidia Xorg driver instead of relying on the modesetting autodetected fallback resolves the crash:

sudo nvidia-xconfig

This generates an /etc/X11/xorg.conf with Driver "nvidia", which avoids the glamor/GBM code path entirely and starts successfully. This suggests the bug is specific to the modesetting + glamor + GBM interaction with the current nvidia-open kernel/userspace pairing, rather than the nvidia driver itself being broken.

Relevant Xorg.0.log output

(II) modeset(G1): Creating default Display subsection in Screen section
"Default Screen Section" for depth/fbbpp 24/32
(II) Applying OutputClass "nvidia" options to /dev/dri/card2
(II) modeset(G1): glamor X acceleration enabled on NVIDIA GeForce RTX 4070/PCIe/SSE2
(EE) modeset(G1): Failed to create pixmap
...
(EE) Segmentation fault at address 0xa8
(EE) Caught signal 11 (Segmentation fault), Server aborting
(EE) Server terminated with error (1). Closing log file.

To Reproduce

1. Install/update to nvidia-open 615.71.09 with no explicit Xorg driver configured (system falls back to the generic modesetting driver).
2. Start an X session (in my case via SDDM's X11 greeter).
3. Xorg loads modesetting, detects the RTX 4070, and enables glamor acceleration.
4. Xorg segfaults shortly after, on the first pixmap allocation.

Bug Incidence

Always

nvidia-bug-report.log.gz

xorg-crash-log-trimmed.log

Removed noise from peripherals.

More Info

No response