Qubes became extremely sluggish after a dom0 update

Thank you for working on this issue so promptly.

So I’ve built and tested a package that included your PR on fedora-44-xfce, but it looks like Xorg won’t start…

journalctl -xe -u qubes-gui-agent -l --no-pager
Aug 20 04:30:13 fedora-44-xfce qubes-gui[630]: open status file: Permission denied
Aug 20 04:30:13 fedora-44-xfce qubes-gui[630]: Waiting on /var/run/xf86-qubes-socket socket...
Aug 20 04:30:14 fedora-44-xfce qubes-gui[630]: Xorg exited in the meantime, aborting
Aug 20 04:30:14 fedora-44-xfce systemd[1]: qubes-gui-agent.service: Main process exited, code=exited, status=1/FAILURE
cat ~/.xsession-errors
X.Org X Server 1.21.1.24
X Protocol Version 11, Revision 0
Build ID: xorg-x11-server 21.1.24-1.fc44 
Current version of pixman: 0.46.2
	Before reporting problems, check http://wiki.x.org
	to make sure that you have the latest version.
Markers: (--) probed, (**) from config file, (==) default setting,
	(++) from command line, (!!) notice, (II) informational,
	(WW) warning, (EE) error, (NI) not implemented, (??) unknown.
(==) Log file: "/home/user/.local/share/xorg/Xorg.0.log", Time: Thu Aug 20 04:30:14 2026
(++) Using config file: "/etc/X11/xorg-qubes.conf"
(==) Using system config directory "/usr/share/X11/xorg.conf.d"
Parse error on line 26 of section Monitor in file /etc/X11/xorg-qubes.conf
	ModeLine VSyncEnd expected
(EE) 
Fatal server error:
(EE) no screens found(EE) 
(EE) 
Please consult the The X.Org Foundation support 
	 at http://wiki.x.org
 for help. 
(EE) Please also check the log file at "/home/user/.local/share/xorg/Xorg.0.log" for additional information.
(EE) 
(EE) Server terminated with error (1). Closing log file.
/usr/bin/xinit: giving up
/usr/bin/xinit: unable to connect to X server: Connection refused
/usr/bin/xinit: server error
nl -ba /etc/X11/xorg-qubes.conf
     1	Section "Module"
     2	        Load "fb"
     3	        Load "glamoregl"
     4	EndSection
     5	
     6	Section "ServerLayout"   
     7	        Identifier     "Default Layout"
     8	        Screen      0  "Screen0" 0 0  
     9	        InputDevice "qubesdev pointer"
    10	EndSection
    11	
    12	Section "Device"
    13	        Identifier  "Videocard0"
    14	        Driver      "dummyqbs"
    15	        VideoRam 8100
    16	        Option "GUIDomID" "0"
    17	        # Render option requires to override default Intel device
    18	        # Option "Render" "/dev/dri/renderD128"
    19	EndSection
    20	
    21	Section "Monitor"
    22	        Identifier "Monitor0"
    23	        HorizSync 0-1
    24		VertRefresh 0-1
    25		Modeline "QBx" 0  1 2 3  1 2 3 
    26	EndSection
    27	
    28	Section "Screen"
    29	        Identifier "Screen0"
    30	        Device     "Videocard0"
    31		Monitor    "Monitor0"
    32	        DefaultDepth     
    33	        SubSection "Display"
    34	                Viewport   0 0
    35	                Depth      
    36			Modes "QBx" 
    37	        EndSubSection
    38	EndSection
    39	
    40	
    41	Section "InputDevice"
    42	        Identifier  "qubesdev pointer"
    43	        Driver      "qubes"
    44	EndSection

I noticed that the Modeline in the “Monitor” section of xorg-qubes.conf looks strange.
On a properly working qube, that section shows as
Modeline "QB1920x1080" 96 1920 1921 1922 1923 1080 1081 1082 1083

It might be PEBKAC. Let’s see the results of ongoing OpenQA tests…