521594 2026-06-17 20:22:22 +0000 SDDM greeter KWin holds /dev/dri/card0 (NVIDIA eGPU), causing user session KWin to fail with “Device or resource busy” on Plasma 6.7 Wayland. 2026-06-29 12:06:52 +0000 1 1 4 Plasma kwin wayland-generic 6.7.0 Fedora RPMs Linux RESOLVED FIXED https://bugs.kde.org/show_bug.cgi?id=521568 NOR normal --- 0 petros.christopoulos kwin-bugs-null akselmo petros.christopoulos xaver.hugl 0 oldest_to_newest 2523960 0 petros.christopoulos 2026-06-17 20:22:22 +0000 DESCRIPTION After upgrading to Plasma 6.7, autologin results in eGPU to fail due to an apparent race condition: SDDM greeter KWin holds /dev/dri/card0 (NVIDIA eGPU), causing user session KWin to fail with “Device or resource busy”. If I log out and back login everything works. If I disable autologin, everything works after I type my password and login. With Plasma 6.6 everything worked fine also with autologin STEPS TO REPRODUCE 1. Set up a system with an Intel iGPU as the primary GPU and an NVIDIA GT 740 (or other Kepler-based) as a secondary eGPU, using the nouveau driver. 2. Enable autologin in SDDM. 3. Reboot 4. Observe: external monitors connected to the eGPU show the boot logo and KDE splash, then turn half‑black/half‑white when Plasma starts. 5. Log out and log back in – monitors work correctly. 6. if you disable autologin and reboot: monitors work correctly after you type the password and login OBSERVED RESULT With autoloign enabled: external monitors connected to the eGPU show the boot logo and KDE splash, then turn half‑black/half‑white when Plasma starts. EXPECTED RESULT With autoloign enabled: external monitors connected to the eGPU show the boot logo and KDE splash and the Plasma session when it starts (worked fine with Plasma 6.6). SOFTWARE/OS VERSIONS Operating System Fedora 44 KDE Operating System: Fedora Linux 44 KDE Plasma Version: 6.7.0 KDE Frameworks Version: 6.27.0 Qt Version: 6.11.1 Kernel Version: 7.0.12-201.fc44.x86_64 (64-bit) Graphics Platform: Wayland Processors: 16 × Intel® Core™ i5-14400 Memory: 40 GiB of RAM (38.8 GiB usable) Graphics Processor 1: Intel® Graphics Graphics Processor 2: GeForce GT 740 ADDITIONAL INFORMATION Workaround - logging out and logging back in always fixes the monitors. - killing KWin from a virtual terminal (pkill -f kwin_wayland) and restarting it / logging back into the session with KWIN_DRM_DEVICES=/dev/dri/card1:/dev/dri/card0 KWIN_DRM_NO_AMS=1 kwin --replace & also works. - disabling autologin (so the greeter is fully terminated before the user session starts) also resolves the issue. What does NOT work - setting KWIN_DRM_DEVICES and KWIN_DRM_NO_AMS=1 in /etc/environment, /etc/environment.d/, or SDDM’s Environment= does not prevent the error. - EnableCompositor=false in SDDM does not help. - a custom Wayland session that sets the variables via env does not prevent the greeter from holding the device. -> the environment variables KWIN_DRM_DEVICES and KWIN_DRM_NO_AMS=1 are correctly read by KWin (verified via cat /proc/$(pidof kwin_wayland)/environ), but KWin still attempts to open card0 and fails. Card mapping ~$ lspci | grep VGA 00:02.0 VGA compatible controller: Intel Corporation Raptor Lake-S UHD Graphics (rev 04) 01:00.0 VGA compatible controller: NVIDIA Corporation GK107 [GeForce GT 740] (rev a1) ~$ ls -l /dev/dri/by-path/ total 0 drwxr-xr-x. 2 root root 120 17. Jun 21:56 . drwxr-xr-x. 3 root root 140 17. Jun 2026 .. lrwxrwxrwx. 1 root root 8 17. Jun 21:56 pci-0000:00:02.0-card -> ../card1 lrwxrwxrwx. 1 root root 13 17. Jun 21:56 pci-0000:00:02.0-render -> ../renderD128 lrwxrwxrwx. 1 root root 8 17. Jun 21:56 pci-0000:01:00.0-card -> ../card0 lrwxrwxrwx. 1 root root 13 17. Jun 21:56 pci-0000:01:00.0-render -> ../renderD129 Logs: ~$ journalctl -b -o short-full | grep -i -E "card0|drm|kwin_wayland|sddm" | tail -100 kwin_wayland[2272]: Failed to open /dev/dri/card0 device (Device or resource busy) (repeated multiple times) kwin_wayland[2272]: Failed to open drm device /dev/dri/card0 systemd[1998]: Started plasma-login-kwin_wayland.service - KDE Window Manager (Login Manager Version). kwin_wayland[2272]: Failed to open drm node: "/dev/dri/card0" systemd[2989]: Starting plasma-kwin_wayland.service - KDE Wayland Compositor... systemd[2989]: Started plasma-kwin_wayland.service - KDE Wayland Compositor. kwin_wayland[3424]: No backend specified, automatically choosing drm kwin_wayland[3424]: Failed to open /dev/dri/card0 device (Device or resource busy) kwin_wayland[3424]: Failed to open /dev/dri/card0 device (Device or resource busy) kwin_wayland[3424]: Failed to open /dev/dri/card0 device (Device or resource busy) (repeated multiple times) 2523962 1 petros.christopoulos 2026-06-17 20:25:30 +0000 Setting KWIN_DRM_DEVICES="/dev/dri/card1:/dev/dri/card0" and KWIN_DRM_NO_AMS=1 in /etc/environment, /etc/environment.d/, or SDDM’s Environment does not prevent the error 2524120 2 akselmo 2026-06-18 09:30:00 +0000 This and https://bugs.kde.org/show_bug.cgi?id=521568 seem related 2527582 3 petros.christopoulos 2026-06-28 08:28:22 +0000 It seems to work well now with Plasma 6.7.1 2527699 4 petros.christopoulos 2026-06-28 18:14:22 +0000 I guess the fix for https://bugs.kde.org/show_bug.cgi?id=521934 fixed this problem as well > Backends/drm: check for the render device in importScanoutBuffer