https://bugs.kde.org/show_bug.cgi?id=466633
Bug ID: 466633
Summary: Black lines or bands flickered horizontally when using
Plasma 5.27.1 on Wayland with nomodeset on the kernel
command line in VMs
Classification: Plasma
Product: kwin
Version: 5.27.1
Platform: Fedora RPMs
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: wayland-generic
Assignee: kwin-bugs-n...@kde.org
Reporter: matt.fagn...@bell.net
Target Milestone: ---
Created attachment 156846
--> https://bugs.kde.org/attachment.cgi?id=156846&action=edit
Recording of the black bands flickering when using Konsole in Plasma 5.27.1 on
Wayland with nomodeset, llvmpipe, and simpledrm in a VM
SUMMARY
I booted the Fedora 38 KDE Plasma live image
Fedora-KDE-Live-x86_64-38-20230224.n.0.iso in a QEMU/KVM VM using GNOME Boxes
with 3D acceleration disabled by selecting Troubleshooting > Start
Fedora-KDE-Live 38 in basic graphics mode in grub which puts nomodeset on the
kernel command line and uses the llvmpipe driver from
mesa-dri-drivers-23.0.0~rc4-3.fc38.x86_64 and the simpledrm driver from the
6.2.0 kernel. Plasma 5.27.1 on Wayland started. I started Konsole. I ran
programs such as sudo dnf upgrade in Konsole. Black lines or bands flickered
horizontally starting at the top of the Konsole window. When I moved the cursor
over the black lines/bands, the path of the cursor showed up as no longer being
black. The black lines/bands showed up lower on the screen sometimes and also
when using other programs or when the background was shown. I'm attaching a
recording of this problem. The problem usually appeared after a few seconds to
a minute of using Konsole.
There were many repeated journal errors like the following when the black
lines/bands were shown.
Feb 28 21:39:45 kwin_wayland[1442]: kwin_wayland_drm: Failed to create AR24
framebuffer: Invalid argument
This problem didn't happen when using the same image with basic graphics mode
with nomodeset, llvmpipe and simpledrm on bare metal, or with llvmpipe and
virtio_gpu, llvmpipe and virgl in VMs, or radeonsi and amdgpu drivers on bare
metal. The problem might be specific to the combination of using nomodeset,
llvmpipe, and simpledrm in VMs.
STEPS TO REPRODUCE
1. Boot a Fedora 37 KDE Plasma installation updated to 2023-2-28 with
updates-testing enabled
2. Log in to Plasma 5.27.1 on Wayland from sddm
3. Download Fedora-KDE-Live-x86_64-38-20230224.n.0.iso from
https://koji.fedoraproject.org/koji/buildinfo?buildID=2159238
4. Install GNOME Boxes if it isn't already with sudo dnf install gnome-boxes
5. Start GNOME Boxes
6. boot the Fedora 38 KDE Plasma live image
Fedora-KDE-Live-x86_64-38-20230224.n.0.iso in a QEMU/KVM VM using GNOME Boxes
with 3D acceleration disabled using the llvmpipe driver
7. In grub, Select Troubleshooting > Start Fedora-KDE-Live 38 in basic graphics
mode
8. Start Konsole in Plasma 5.27.1 on Wayland in the VM
9. Run sudo dnf upgrade in Konsole
10. Move the mouse cursor around over the top of Konsole until the black
lines/bands flicker
OBSERVED RESULT
Black lines or bands flickered horizontally when using Plasma 5.27.1 on Wayland
with nomodeset on the kernel command line in VMs
EXPECTED RESULT
No black lines or bands would appear on the screen
SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Fedora 38
(available in About System)
KDE Plasma Version: 5.27.1
KDE Frameworks Version: 5.103.0
Qt Version: 5.15.8
ADDITIONAL INFORMATION
The mouse cursor in the VM seemed to be lagging behind the cursor of the host
when using the nomodeset, llvmpipe, simpledrm combination with the problem, but
not otherwise.
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