Many services in my LAN are provided by virtual KVM/QEMU-guests of a dedicated KVM-server-host. More special services are provided by local KVM-guests on Workstations. All my virtualized systems get normally equipped with a qxl/spice-combination to provide a graphical interface - which can be used on the KVM-host or by remote spice clients. A direct graphical access via a spice client is required only seldomly (besides ssh connections) - but in some cases or situations it is useful, if not mandatory.
Recently, I upgraded both the central KVM-Server, its guests and also guests on workstations from Opensuse Leap 42.3 to Leap 15.0. Unfortunately, after the upgrade no graphical access was possible any longer to my guest-systems via spice-clients (as virt-viewer or the graphical spice-console of virt-manager).
After some tests I found out that this was due to missing KMS on the guest systems - present qxl-modules, however, do require KMS. But, if you update/install from an ISO image "KMS" may not be compatible with the graphical SuSE installer. And due to previous configurations "nomodeset" may be a kernel parameter used in the installation before the upgrade. Here is the story ...
The problem: Unreadable, freezing interfaces on spice-clients
Normally, I upgrade by a 5-step sequence: 1) Update all packets, 2) reduce repositories to the Update- and OSS-repository, 3) switch to the repositories of the new distribution, 4) "zypper dup --download-only", 5) "zypper --no-refresh dup" (see e.g. how-to-upgrade-from-opensuse-leap-422-to-423/).
The KVM server-host itself gave me no major problem during its upgrade. Also the KVM-guests - with their server-services - seemed to work well. Most often, I access the KVM-guest-systems via ssh to perform regular administration tasks. So, I did not even notice for a while that something was wrong with the qxl/spice-configuration. But when I used "virt-manager" in an "ssh -X" session from my workstation to the KVM-server and tried to open the graphical console for a guest there, I got an unreadable virtual screen, which froze instantly and did no longer react to any input - special commands sent via "virt-manager" to switch to a non-graphical console terminal were ignored. The same happened with "virt-viewer" and/or when I executed virt-manager directly on the graphical screen of the KVM-server.
Independent test with a new installation of a "Leap 15"-guest-system
To find out more I tested a new installation of Leap 15 on my Leap 15 workstation as a KVM-server. I chose a guest system configuration with standard equipment - among other things qxl/spice-components. The installation was started via the "virt-installer" component of virt-manager. I used an ISO-image of the Leap 15 installation image.
First thing I stumbled across was that I had to use a "No KMS" for the text console setting on the first screen of the Opensuse installer (see the options for the graphical setup there; F3-key). Otherwise the installer froze during the first "udev" checks. I knew this effect already from installations on some physical systems. Note that the choice of "No KMS" leads to an kernel parameter entry "nomodeset" in the command line for the kernel call in the Grub2 configuration (see the file /etc/default/grub).
Such a full new installation lead into a void. SuSE's graphical installer itself worked perfectly with high resolution. However, after a restart of the freshly installed guest-system the switch to the graphical screen lead to a flickering virtual screen and the graphical display of the SDDM login manager never appeared.
Still and luckily, it was possible to login as root and execute a "init 3" command - which brought me to a working, non-flickering ASCII console interface (TTY1).
I had experienced this type of behavior before, too, on some real physical systems. I recommend Leap users to be prepared: activate ssh-services during installation and open the firewall for ssh-ports! The SuSE-installer allows for such settings on its summary screen for the installation configuration. This gives you a chance to switch to a working text console (init 3) from a remote SSH-command line - if the graphical console does not allow for any input.
Tests 2: Upgrade to latest KVM / QEMU / libvirt - versions of the "Virtualization" repository
An installation of the cutting edge versions of KVM/QEMU and spice sever and client software did not change anything - neither on my dedicated KVM-server-system and its upgraded guests nor on my workstation with the fresh Leap 15 test-guest.
Repair of the older upgraded guest-systems
The emulated "hardware" of my older (upgraded) guest-systems, which stem from an OS 13.2 era, is a bit different from the equipment of the newest test guest. On these older systems I still had the choice to use a cirrus, vga or vmwvga graphics. Interestingly, these drivers do not provide the performance of qxl - but they worked at least with the virtual spice client displays.
One central question was whether the QXL driver - more precisely the corresponding kernel module "qxl" - was loaded at all. Answer for the guests on the central KVM-server: No, it was not.
So, on the first guest I simply tried "modprobe qxl" - and hey - the module loaded. An "init 5" then gave me the aspired graphical screen.
Later I checked that actually no "nomodeset" parameter was set in these guests. So, something went "wrong" with the system's startup-configuration during the upgrade procedure. I have no real clue why - as the qxl-module was loaded without problems on the previous Leap 42.3 installations.
For Opensuse Leap the wrapper-script "mkinitrd" transfers a running configuration with its loaded kernel modules via "dracut" into a suitable and permanent initramfs/initrd- and systemd-startup configuration. So, issue "mkinitrd" after a successful test of a qxl/spice-interface.
Repair of the freshly installed Leap 15 guest-system
On the freshly installed Leap 15 guest client on my workstation things were slightly different: The qxl-module did not load there. A "modinfo qxl" shows you parameters you can apply. The right thing to do there was to try
modprobe qxl modeset=1
This worked! Then I eliminated the "nomodeset"-parameter from the "GRUB_CMDLINE_LINUX_DEFAULT"-entry in the file "/etc/default/grub" and started "mkinitrd" to get a stable permanent startup-configuration (via dracut) which booted the guest into graphical mode afterwards.
Adjustment of the TTYs and KDE
As soon as you have a reasonable configuration, you may want to adjust the screen dimensions of the text consoles tty1 to tty6, the sddm-login-screen and the KDE or Gnome screen. These are topics for separate articles. See, however, previous articles in this blog on KVM guests for some hints.
For the text console TTYs try reasonable settings for the following entries in the "/etc/default/grub" - below e.g. for a resolution of "1680x1050":
GRUB_CMDLINE_LINUX_DEFAULT=" .... OTHER PARAMETERS ...... video=1680x1050"
Do not forget to execute "mkinitrd" again afterwards!
For KDE adjustments a user can use the command "systemsettings5" and then specify screen resolutions in the dialog for "display and monitors".
The graphical installer of Opensuse, but also upgrade-procedures on working virtual KVM/QEMU guests with qxl/spice can lead to situations where KMS is or must be deactivated both for physical and virtual systems. As a consequence the "qxl-module" may not be loadable automatically afterwards. This can lead to failures during the start of a graphical qxl/spice-interface for local and remote spice-clients.
The remedy is to remove any "nomodeset"-parameter which may be a part of the entry for "GRUB_CMDLINE_LINUX_DEFAULT" in the file "/etc/default/grub".
For tests of the qxl-driver try loading the qxl-module with "modprobe qxl modeset=1". After a successful start a graphical interface use "mkinitrd" (whilst the qxl-module is loaded!) to establish a permanent configuration which loads "qxl" during system start.