https://bugs.kde.org/show_bug.cgi?id=528043
Bug ID: 528043
Summary: NVIDIA-primary (KWIN_DRM_DEVICES) with Intel eDP:
artifacts in damaged regions with Vulkan multi-GPU
copy; fine with KWIN_ALLOW_VULKAN_MGPU_COPIES=0
Classification: Plasma
Product: kwin
Version First unspecified
Reported In:
Platform: CachyOS
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: platform-drm
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Target Milestone: ---
STEPS TO REPRODUCE
1. Hybrid laptop: Intel Raptor Lake-S UHD (i915) drives the internal eDP panel,
NVIDIA RTX 4080 Laptop drives an external DisplayPort monitor.
2. Start the Plasma Wayland session with the NVIDIA GPU as primary:
KWIN_DRM_DEVICES=/dev/dri/dgpu-card:/dev/dri/igpu-card (dgpu-card -> NVIDIA,
igpu-card -> Intel, udev symlinks).
3. Type in a text editor or terminal, or drag a window, on the internal eDP
panel.
OBSERVED RESULT
On the internal eDP panel (Intel), artifacts appear in the regions that change:
around text while typing and along windows while they are moved. The external
monitor driven by the NVIDIA GPU looks fine.
EXPECTED RESULT
No artifacts on the eDP panel, as before.
ADDITIONAL INFORMATION
- Setting KWIN_ALLOW_VULKAN_MGPU_COPIES=0 (forcing the EGL copy path) makes the
artifacts disappear completely. KWin's log confirms the variable is applied:
KWIN environment variables: QList("KWIN_ALLOW_VULKAN_MGPU_COPIES=0",
"KWIN_DRM_DEVICES=/dev/dri/dgpu-card:/dev/dri/igpu-card")
- Not PSR: still reproduces with i915.enable_psr=0.
- Still reproduces on 6.8.2, which includes 6783f961 (fix for bug 527544).
- Regression window: worked with kwin 6.8.1 (Arch 6.8.1-1) + Mesa 26.2.4 +
linux 7.3.0-3. Started after a single update to kwin 6.8.1-2 (Arch build adding
64850f81 and 83ad3261, "multigpuswapchain"), Mesa 26.2.5 and linux 7.3.0-4.
Reverting the whole update fixed it. I have not isolated kwin from Mesa: with
83ad3261 the copy to the Intel GPU now goes through Vulkan (anv), so either the
KWin change or anv 26.2.5 could be responsible. Happy to test a downgrade of
vulkan-intel alone, or patches.
- Related, but different: bug 527544 (same NVIDIA-primary + Intel eDP layout,
other symptoms), bugs 527591 and 527604 (cited in 83ad3261).
SOFTWARE/OS VERSIONS
Operating System: CachyOS (Arch-based, rolling)
KDE Plasma Version: 6.8.2
KDE Frameworks Version: 6.31.0
Qt Version: 6.12.0
Kernel Version: 7.3.0-4-cachyos (64-bit)
Graphics Platform: Wayland
Mesa: 26.2.5 (vulkan-intel 26.2.5)
NVIDIA driver: 615.78.08 (open kernel modules)
HARDWARE
ASUS ROG Strix G16 (G614JZ), Intel Core i9-13980HX
GPU 1: Intel Raptor Lake-S UHD Graphics [8086:a788], i915, internal eDP-1
2560x1600 @ 240 Hz
GPU 2: NVIDIA GeForce RTX 4080 Laptop (AD104M) [10de:27e0], external DP-3
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