https://bugs.kde.org/show_bug.cgi?id=525501
Bug ID: 525501
Summary: no login with KVM switch
Classification: Plasma
Product: plasmashell
Version First 6.7.4
Reported In:
Platform: CachyOS
OS: Linux
Status: REPORTED
Severity: critical
Priority: NOR
Component: Session Management
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected]
Target Milestone: 1.0
Created attachment 195968
--> https://bugs.kde.org/attachment.cgi?id=195968&action=edit
"Screenshot" of what I'm seeing on screen
DESCRIPTION
I recently bought a KVM switch to use my setup for work (laptop) and my gaming
pc.
The KVM switch works flawlessly with my work laptop but sadly not with CachyOS
or more precisely KDE.
All monitors are detected when connected through 1 DP cable using the MST
protocol. I verified this working on Windows on the gaming machine (although
there is some flickering).
Now on Cachy I get a blank screen with the KDE mouse but no login.
I’m able to open a tty via CTRL+ALT+F2 and the logs say (see screenshot).
I tried looking for help online but couldn’t find good help. There’s also a
section in KDE’s troubleshooter for this
https://userbase.kde.org/Troubleshooting/Black_Screen
But it didn’t help me. I also read that MST was a troublechild on Linux in the
past but that was ~2014. I expect it to just work.
Current workaround is to plug the devices in directly to the pc. But this
defeats the purpose of a KVM switch.
I tried looking for help online but couldn’t find good help. There’s also a
section in KDE’s troubleshooter for this Troubleshooting/Black Screen - KDE
UserBase Wiki
But it didn’t help me. I also read that MST was a troublechild on Linux in the
past but that was ~2014. I expect it to just work.
Error (written by hand) for SEO:
qt.qpa.xcb: could not connect to display
qt.qpa.plugin: From 6.5.0, xcb-cursor0 orlbxcb-cursor0 is needed to load Qt xcb
platform plugin
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it
was found.
STEPS TO REPRODUCE
1. Connect 3(?) Monitors (1x DP + 2x HDMI) to a KVM switch (I'm using
https://www.amazon.de/dp/B0H3P29N5R)
2. Connect 1x DP to the KVM switch
3. Getting a black screen.
OBSERVED RESULT
* Works on Windows
* No Login screen in Cachy with KDE
* Multi montior still working
* I'm seeing the KDE mouse
* CTRL+ALT+F2 still works
EXPECTED RESULT
Seemless experience as on Windows
SOFTWARE/OS VERSIONS
Operating System: CachyOS Linux
KDE Plasma Version: 6.7.4
KDE Frameworks Version: 6.29.0
Qt Version: 6.11.2
Kernel Version: 7.2.3-1-cachyos (64-bit)
Graphics Platform: Wayland
Processors: 24 × AMD Ryzen 9 9900X 12-Core Processor
Memory: 64 GiB of RAM (60.4 GiB usable)
Graphics Processor 1: NVIDIA GeForce RTX 4060 Ti
Graphics Processor 2: AMD Ryzen 9 9900X 12-Core Processor
ADDITIONAL INFORMATION
* Discuss in Cachy forum
https://discuss.cachyos.org/t/kde-plasmashell-no-login-with-kvm-switch/35471/3
(Description mostly copied from there)
* Current workaround is to plug the devices in directly to the pc. But this
defeats the purpose of a KVM switch
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