https://bugs.kde.org/show_bug.cgi?id=523895
Bug ID: 523895
Summary: Xwayland never starts when a Vulkan implicit layer
(e.g. MangoHud) is enabled globally
Classification: Plasma
Product: kwin
Version First 6.6.90
Reported In:
Platform: CachyOS
OS: Linux
Status: REPORTED
Severity: major
Priority: NOR
Component: wayland-generic
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
DESCRIPTION
Since 6.6.90, kwin_wayland creates a VkInstance at startup which seems to cause
Vulkan implicit layers (example here: MangoHud) to be loaded into the
compositor process. With MangoHud enabled globally, kwin_wayland never spawns
Xwayland. The Plasma session comes up fully, Wayland clients are fine, but no
X11 client can connect and no Xwayland process is ever created. No issues on
6.6.5, broken on 6.6.90, still broken on 6.7.4. Downgrading only kwin with the
rest of the Plasma stack left updated fixes it. Disabling MangoHud for the
compositor explicitly via env in plasma-kwin_wayland.service also fixes it.
STEPS TO REPRODUCE
1. Enable MangoHud globally (env var / implicit Vulkan layer active for all
apps)
2. Log into a Plasma Wayland session
3. Start any X11 application
OBSERVED RESULT
- Application exits with "cannot open display :0".
- pgrep -a Xwayland is empty. Xwayland is never spawned at all.
- kwin_wayland is running normally with the wrapper's fds:
/usr/bin/kwin_wayland --wayland-fd 7 --socket wayland-0 --xwayland-fd 8
--xwayland-fd 9 --xwayland-display :0 --xwayland-xauthority ... --xwayland
- MangoHud is resident in the compositor:
grep -i mango /proc/$(pgrep -x kwin_wayland)/maps
- Journal shows MangoHud initialising immediately before KWin's own Vulkan
message.
- No error is logged by the Xwayland launcher.
EXPECTED RESULT
Xwayland starts.
CONFIRMED WORKAROUND
Adding any of the following to plasma-kwin_wayland.service makes Xwayland
start:
DISABLE_MANGOHUD=1
MANGOHUD=0
VK_LOADER_LAYERS_DISABLE=VK_LAYER_MANGOHUD_overlay
SOFTWARE/OS VERSIONS
Operating System: CachyOS
KDE Plasma Version: 6.6.90 and later (tested through 6.7.4), 6.6.5 unaffected
KDE Frameworks Version: 6.28.0
Qt Version: 6.11.1
ADDITIONAL INFORMATION
amdgpu, single device
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