Open a guest inside KVM and put it full screen. 
Watch a stream.
The whole guest vanishes (crashes) however the OS itself is still running in
background and can be reopened. It is only its display output that does crash. 
This is the case since the mesa update of today, but I am not sure if mesa is
related. 

What I am getting in the journal is as follows (and everytime the same):



lug 02 18:17:11 localhost systemd[1]:
run-credentials-systemd\x2dtmpfiles\x2dclean.service.mount: Deactivated
successfully.
lug 02 18:17:11 localhost systemd[1]: Finished Cleanup of Temporary
Directories.
lug 02 18:17:11 localhost systemd[1]: systemd-tmpfiles-clean.service:
Deactivated successfully.
lug 02 18:17:11 localhost systemd-tmpfiles[8659]:
/usr/lib/tmpfiles.d/suse.conf:10: Duplicate line for path "/run/lock",
ignoring.
lug 02 18:17:11 localhost systemd[1]: Starting Cleanup of Temporary
Directories...
lug 02 18:15:50 localhost plasmashell[2797]:
file:///usr/lib64/qt5/qml/org/kde/plasma/core/private/DefaultToolTip.qml:69:13:
QML Label: Binding loop detected for property "verticalAlignment"
lug 02 18:15:25 localhost kded5[2763]: Service  ":1.182" unregistered
lug 02 18:15:25 localhost kded5[2763]: Registering ":1.182/StatusNotifierItem"
to system tray
lug 02 18:15:25 localhost virt-manager[8565]: Warning no automount-inhibiting
implementation available
lug 02 18:15:23 localhost virtqemud[2218]: Failed to connect socket to
'/var/run/libvirt/virtnodedevd-sock': File o directory non esistente
lug 02 18:15:23 localhost virtqemud[2218]: Failed to connect socket to
'/var/run/libvirt/virtnetworkd-sock': File o directory non esistente
lug 02 18:15:23 localhost virtqemud[2218]: Failed to connect socket to
'/var/run/libvirt/virtnodedevd-sock': File o directory non esistente
lug 02 18:15:23 localhost virtqemud[2218]: Failed to connect socket to
'/var/run/libvirt/virtnetworkd-sock': File o directory non esistente
lug 02 18:15:23 localhost virtqemud[2218]: Failed to connect socket to
'/var/run/libvirt/virtnodedevd-sock': File o directory non esistente
lug 02 18:15:23 localhost virtqemud[2218]: Failed to connect socket to
'/var/run/libvirt/virtnetworkd-sock': File o directory non esistente
lug 02 18:15:23 localhost kded5[2763]: Registering
":1.179/org/ayatana/NotificationItem/virt_manager" to system tray
lug 02 18:15:23 localhost virt-manager[8565]: AT-SPI: Error retrieving
accessibility bus address: org.freedesktop.DBus.Error.ServiceUnknown: The name
org.a11y.Bus was not provided by any .service files
lug 02 18:15:23 localhost systemd[2604]: Started Gestore macchine virtuali.
lug 02 18:15:22 localhost plasmashell[2797]: QString::arg: 2 argument(s)
missing in virt-manager
lug 02 18:15:22 localhost plasmashell[2797]: kf.service.services:
KApplicationTrader: mimeType "x-scheme-handler/file" not found
lug 02 18:14:42 localhost akonadi_maildir_resource[3685]: "Item query returned
empty result set"
lug 02 18:14:42 localhost akonadiserver[3090]: org.kde.pim.akonadiserver:
Handler exception when handling command FetchItems on connection
akonadi_maildir_resource_0 (0x564d430fc990) : Item query returned empty result
set
lug 02 18:14:42 localhost akonadiserver[3090]: org.kde.pim.akonadiserver:
Handler exception when handling command FetchItems on connection MailFilter
Kernel ETM (0x564d431045b0) : Item query returned empty result set
lug 02 18:14:42 localhost akonadiserver[3090]: org.kde.pim.akonadiserver:
Handler exception when handling command FetchItems on connection KMail Kernel
ETM (0x564d43106630) : Item query returned empty result set
lug 02 18:14:42 localhost kontact[2947]: "Item query returned empty result set"
lug 02 18:14:42 localhost akonadi_mailfilter_agent[3701]: "Item query returned
empty result set"
lug 02 18:14:42 localhost akonadi_archivemail_agent[3679]: "Item query returned
empty result set"
lug 02 18:14:42 localhost akonadiserver[3090]: org.kde.pim.akonadiserver:
Handler exception when handling command FetchItems on connection Archive Mail
Kernel ETM (0x564d43105080) : Item query returned empty result set
lug 02 18:13:28 localhost systemd[1]: snapperd.service: Consumed 2.642s CPU
time.
lug 02 18:13:28 localhost systemd[1]: snapperd.service: Deactivated
successfully.
lug 02 18:13:24 localhost plasmashell[2797]: error creating screencast "Could
not find window id {825c6f80-9d42-4b68-a7b9-dafc15edb9eb}"
lug 02 18:13:24 localhost kded5[2763]: Service  ":1.175" unregistered
lug 02 18:13:24 localhost systemd[2604]:
app-virt\x2dmanager-3351630286ab4fa08f01f137ea4a8683.scope: Consumed 3min
6.511s CPU time.
lug 02 18:13:24 localhost virtqemud[2218]: End of file while reading data:
Errore di input/output
lug 02 18:13:24 localhost virt-manager[4380]: Error flushing display: Risorsa
temporaneamente non disponibile

End of excerpt. 

When opening the manager the OS is running, double click restores, the stream
continued normally. It is hence the full screen output that is troubled. As I
am not even understanding what is happening, I can only for the time being,
give you this output.