Random complete freeze when using KVM HDMI switch

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1

Hello,

I am facing random complete freeze of Kunbuntu when using KVM HDMI switch. This happens with 25.10 but also with previous versions including LTS.

When the issue occurs, i don’t have access to anything: keyboard, mouse… the only solution is to restart using power button. The problem can happen several times per day or not…

How could this be fixed please?

From the journal logs i get:

nov. 05 08:51:23 papadou kactivitymanagerd[2684]: qt.qpa.wayland: There are no outputs - creating placeholder screen
nov. 05 08:51:23 papadou polkit-kde-authentication-agent-1[2689]: qt.qpa.wayland: There are no outputs - creating placeholder screen
nov. 05 08:51:23 papadou plasmashell[2656]: kde.plasmashell: requesting unexisting screen available rect -1
nov. 05 08:51:23 papadou kded6[2627]: qt.qpa.wayland: There are no outputs - creating placeholder screen
nov. 05 08:51:24 papadou DiscoverNotifier[2942]: qt.qpa.wayland: There are no outputs - creating placeholder screen
nov. 05 08:51:24 papadou xdg-desktop-portal-kde[3189]: qt.qpa.wayland: There are no outputs - creating placeholder screen
nov. 05 08:51:24 papadou systemsettings[3067]: qt.qpa.wayland: There are no outputs - creating placeholder screen
nov. 05 08:51:24 papadou kdeconnectd[2902]: qt.qpa.wayland: There are no outputs - creating placeholder screen
nov. 05 08:51:24 papadou kwin_wayland_wrapper[2495]: kwin_xwl: Could not find a matching X RandR CRTC/output to set as primary for KWin::PlaceholderOutput(0x622284079db0, name="Placeholder-1", geometry=QRect(0,0 1920x1080), scale=1)
nov. 05 08:51:24 papadou kwin_wayland_wrapper[2495]: kwin_xwl: Could not find a matching X RandR CRTC/output to set as primary for KWin::PlaceholderOutput(0x622284079db0, name="Placeholder-1", geometry=QRect(0,0 1920x1080), scale=1)
nov. 05 08:51:24 papadou konsole[3066]: qt.qpa.wayland: There are no outputs - creating placeholder screen
nov. 05 08:51:24 papadou org_kde_powerdevil[2690]: qt.qpa.wayland: There are no outputs - creating placeholder screen
nov. 05 08:51:24 papadou plasmashell[2656]: qt.qpa.wayland: There are no outputs - creating placeholder screen
nov. 05 08:51:24 papadou org_kde_powerdevil[2690]: [  8913] Removing connected display on bus 1
nov. 05 08:51:24 papadou org_kde_powerdevil[2690]: [  8913] Emitting DDCA_Display_Status_Event[2986.607:  DDCA_EVENT_DISPLAY_DISCONNECTED, card1-HDMI-A-1, dref: DDCA_Display_Ref[11], io_path:/dev/i2c-1, ddc working: false]
nov. 05 08:51:24 papadou org_kde_powerdevil[2690]: [  8913] libddcutil callback thread 0x74fed8013440 started
nov. 05 08:51:24 papadou org_kde_powerdevil[2690]: [  8913] Started 1 event callback thread(s)
nov. 05 08:54:03 papadou rtkit-daemon[2300]: Supervising 10 threads of 7 processes of 1 users.
nov. 05 08:54:03 papadou rtkit-daemon[2300]: Supervising 10 threads of 7 processes of 1 users.
nov. 05 08:54:19 papadou PackageKit[8635]: daemon quit
nov. 05 08:54:19 papadou systemd[1]: packagekit.service: Deactivated successfully.​
2

This happens with 25.10

It might be fixed in 6.5.

Did you try the ppa to get Plasma 6.5?

What you experienced seem like a kwin crash.
You should be able to have a trace with:

coredumpctl debug kwin_wayland -A "-ex bt -ex quit" |& tee backtrace.txt

(Replace with kwin_x11 if you use x11)
And share the backtrace file.
Ref: Debug symbols for all!

3

Hello & thanks for your reply.

i have tried this command line but its output is ‘no match found’ which likely means there are no core dump available.

Why do you think it would be fixed with Plama 6.5 please?

Thanks,

4

Hello,

I have followed your advice and upgraded to plasma 6.5 using the ppa.

So far the issue did not happen again.

I have noticed that each time i switch screen back to kde i have a small pop up from kded saying that a screen got detected.

Thanks,

5

That might be how your KVM works.

My own KVM switch works differently. As I switched computers, screens are still there even though they don’t output anything, so I don’t get notifications.

You can disable this notification if that’s annoying.

6

Hello,

Unfortunately, it crashed again this morning, here are the journal logs.

There are no core dumps generated, it just freezes the entire gui, no mouse or keyboard available.

Should I file a bug somewhere ?

Thanks,

nov. 12 07:32:16 papadou polkit-kde-authentication-agent-1[2701]: qt.qpa.wayland: There are no outputs - creating placeholder screen
nov. 12 07:32:16 papadou kded6[2625]: qt.qpa.wayland: There are no outputs - creating placeholder screen
nov. 12 07:32:16 papadou plasmashell[2656]: kde.plasmashell: requesting unexisting screen available rect -1
nov. 12 07:32:16 papadou kactivitymanagerd[2687]: qt.qpa.wayland: There are no outputs - creating placeholder screen
nov. 12 07:32:16 papadou DiscoverNotifier[2846]: qt.qpa.wayland: There are no outputs - creating placeholder screen
nov. 12 07:32:16 papadou konsole[3005]: qt.qpa.wayland: There are no outputs - creating placeholder screen
nov. 12 07:32:16 papadou kdeconnectd[2803]: qt.qpa.wayland: There are no outputs - creating placeholder screen
nov. 12 07:32:16 papadou dolphin[3003]: qt.qpa.wayland: There are no outputs - creating placeholder screen
nov. 12 07:32:16 papadou rclone-browser[3006]: qt.qpa.wayland: Creating a fake screen in order for Qt not to crash
nov. 12 07:32:16 papadou xdg-desktop-portal-kde[3155]: qt.qpa.wayland: There are no outputs - creating placeholder screen
nov. 12 07:32:16 papadou krunner[16220]: qt.qpa.wayland: There are no outputs - creating placeholder screen
nov. 12 07:32:16 papadou libreoffice[16371]: qt.qpa.wayland: There are no outputs - creating placeholder screen
nov. 12 07:32:16 papadou baloorunner[16283]: qt.qpa.wayland: There are no outputs - creating placeholder screen
nov. 12 07:32:16 papadou plasma-discover[13869]: qt.qpa.wayland: There are no outputs - creating placeholder screen
nov. 12 07:32:16 papadou org_kde_powerdevil[2702]: qt.qpa.wayland: There are no outputs - creating placeholder screen
7

This seems like a KWin freeze.

Yes please, for kwin https://bugs.kde.org

Report your kscreen-doctor -o and kinfo command line output.

The output for journalctl -t kwin_wayland would also be interesting.

The creating placeholder screen is normal business when there are no screens, few applications can de with it in practise so a fake screen is exposed to them, until a real screen is available again.

This happens with 25.10 but also with previous versions including LTS.

Something you might want to try , is the Kubuntu PPA to try Plasma 6.5. How to Upgrade to KDE Plasma 6.5 on Kubuntu 25.10 - OMG! Ubuntu

8

Hello,

I have submitted this bug:

9

Hello,

This bug is not moving. Have I done something wrong when submitting it please?

Thanks,

10

I have a KVM switch that works perfectly.

So the issue is probably due to your particular KVM switch having a bug itself or triggering one in kwin.

So Please report the KVM you have.
And add this to your bug.

11

Hello,

Thanks for your reply.

My KVM is a very basic one: SGEYR SGDK302D HDMI KVM Switch 2 Port.

I have tried another one (also very basic) and it has the same kind of problem.

I will add this to the bug i raised.

Thanks,

12

Hello,

today the KVM switch action crashed plamashell with the following stack trace.

I have attached the backtrace from the dump to the bug ticket.

Thanks,