https://bugs.kde.org/show_bug.cgi?id=521847
Bug ID: 521847
Summary: Regression (6.7.0): KWin Wayland hard-freezes
secondary GPU (NVIDIA Xid 31 MMU fault) on
brightness change in Intel+NVIDIA Optimus
multi-monitor setup
Classification: Plasma
Product: kwin
Version First unspecified
Reported In:
Platform: CachyOS
OS: Linux
Status: REPORTED
Severity: crash
Priority: NOR
Component: multi-screen
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
On a hybrid Intel(iGPU)+NVIDIA(dGPU) laptop with an external monitor wired to
the
NVIDIA GPU, changing display brightness under Wayland instantly freezes the
whole
session. The NVIDIA-driven external display freezes first, the cursor
survives a
moment on the Intel-driven panel, then total lock. SysRq/VT-switch
unresponsive;
only a hard power-off recovers.
Regression: 100% stable on Plasma/KWin 6.6.5 for days. Freezes started on the
first
session running 6.7.0 (and 6.7.0-3.1). Downgrading ONLY kwin to 6.6.5 removes
the
freeze entirely (same kernel, same NVIDIA driver) -> regression is in kwin
6.7.0.
Key evidence it is NOT the NVIDIA driver:
The kernel fault is byte-for-byte identical across TWO different NVIDIA
branches:
NVRM: Xid (PCI:0000:01:00): 31, name=kwin_wayland, MMU Fault: ENGINE
GRAPHICS
GPC2 GPCCLIENT_PROP_0 faulted @ 0x0_07e40000, FAULT_PTE
ACCESS_TYPE_VIRT_READ
Reproduced on nvidia-open 610.43.02 AND 580.159.04 -> kwin submits invalid
GPU
work to the secondary GPU. Likely same family as bug 521161 (closed as
upstream/
NVIDIA), but the driver-independence + clean 6.6.5->6.7.0 regression point to
kwin.
Hardware:
- iGPU: Intel TigerLake-H UHD [8086:9a68] (i915) -> eDP-1 (internal panel)
- dGPU: NVIDIA RTX 3060 Mobile GA106 [10de:2520] -> HDMI-A-1 (external
monitor)
Steps to reproduce:
1. Optimus laptop, external monitor connected via HDMI (wired to the dGPU).
2. Wayland session.
3. Change display brightness (powerdevil backlighthelper) -> instant hard
freeze.
Software:
- KWin 6.7.0-3.1 (crash) / 6.6.5-4.1 (stable). Plasma 6.7.0. Qt 6.11.1.
- Kernel 7.0.12. Mesa 26.1.2. CachyOS (Arch-based). Wayland.
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