https://bugs.kde.org/show_bug.cgi?id=517524
Bug ID: 517524
Summary: KWin fullscreen unredirection freezes seat when using
NVIDIA PRIME render offload on X11
Classification: Plasma
Product: kwin
Version First 6.6.1
Reported In:
Platform: CachyOS
OS: Linux
Status: REPORTED
Severity: major
Priority: NOR
Component: compositing
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
Created attachment 190639
--> https://bugs.kde.org/attachment.cgi?id=190639&action=edit
a detailed description of the problem
STEPS TO REPRODUCE
1. Set up an X11 session with NVIDIA PRIME render offload active. This was
tested on
a Linux multiseat setup where seat-1 uses Intel HD Graphics 4000 as DRM
master and
display output, with NVIDIA RTX 4060 Ti exposed via PRIME render offload:
DRI_PRIME=pci-0000_01_00_0, __NV_PRIME_RENDER_OFFLOAD=1,
__VK_LAYER_NV_optimus=NVIDIA_only
2. Launch any 3D game or application via Steam/Proton with PRIME offload active
3. Allow the application to cover 100% of the screen (true fullscreen or
borderless
at exact screen resolution)
OBSERVED RESULT
The seat freezes immediately. The last rendered frame stays visible (no black
screen).
No input is accepted. The freeze is 100% reproducible on every attempt.
KEY FINDING: setting the window to 1 pixel less than full screen height (e.g.
1920x1079
instead of 1920x1080) completely prevents the freeze. This isolates the cause
to KWin's
fullscreen unredirection mechanism — with 1 pixel of desktop visible KWin keeps
compositing and no conflict occurs. When the window covers 100% of the screen,
KWin
activates unredirection and attempts to give the window direct framebuffer
access, which
conflicts with the Intel GPU being the DRM master while the window renders on
the NVIDIA.
EXPECTED RESULT
Applications using PRIME render offload should be able to cover the full screen
without
freezing. KWin should detect that unredirection is not viable when the
rendering GPU
differs from the display GPU (PRIME offload scenario) and skip it.
SOFTWARE/OS VERSIONS
Linux/KDE Plasma: CachyOS Linux (rolling)
KDE Plasma Version: 6.6.1
KDE Frameworks Version: 6.23.0
Qt Version: 6.10.2
Kernel: 6.18.8-1-cachyos (64-bit)
GPU (rendering): NVIDIA GeForce RTX 4060 Ti 16GB [10de:2805], driver 590.48.01
GPU (display/DRM master): Intel HD Graphics 4000 [8086:0162] (IvyBridge)
Mesa: 25.3.5-2
ADDITIONAL INFORMATION
This issue was previously reported as Bug #464770 and closed WORKSFORME due to
no
response. This report confirms the issue persists in Plasma 6.
Tested games: Beyond Two Souls (Proton), Slime Rancher (Proton).
The issue does not occur on the primary seat where NVIDIA is the DRM master.
The issue does not occur on Wayland (consistent with Wayland not using
unredirection).
--
You are receiving this mail because:
You are watching all bug changes.
