When I use virt-manager to connect to a remote host (qemu+ssh) all works fine except the vnc console, that is always blank. Only for a short instant one can spot the sliders on right side. If I try to connect to the same host (all kvm based) with, say, ubuntu or debian clients all works just fine. This happens on different host machines. I tried with different virt-manager versions, on my gentoo machine, and different versions of libvirt and related libs, bu the result is the same. Any hint about how to debug the issue will be most useful; right now I can't be sure if it can be a tunnel issue, a graphic lib issue or whatever. If I try to connect to remote kvm machine using a separate ssh tunnel and vnc, I get no issues. Reproducible: Always app-emulation/libvirt-1.2.17-r4:0/1.2.17 app-emulation/virt-manager-1.2.1:0 calvin ~ # emerge --info Portage 2.2.20 (python 3.4.3-final-0, default/linux/amd64/13.0/desktop/kde/systemd, gcc-4.9.3, glibc-2.21-r1, 4.1.3 x86_64) ================================================================= System uname: Linux-4.1.3-x86_64-Intel-R-_Core-TM-_i5-3427U_CPU_@_1.80GHz-with-gentoo-2.2 KiB Mem: 8091780 total, 4346956 free KiB Swap: 8386556 total, 8386556 free Timestamp of repository gentoo: Fri, 31 Jul 2015 06:45:01 +0000 sh bash 4.3_p39 ld ld di GNU (Gentoo 2.25.1 p1.0) 2.25.1 app-shells/bash: 4.3_p39::gentoo dev-java/java-config: 2.2.0::gentoo dev-lang/perl: 5.22.0::gentoo dev-lang/python: 2.7.10::gentoo, 3.3.5-r1::gentoo, 3.4.3::gentoo dev-util/cmake: 3.3.0::gentoo dev-util/pkgconfig: 0.28-r3::gentoo sys-apps/baselayout: 2.2::gentoo sys-apps/openrc: 0.17::gentoo sys-apps/sandbox: 2.6-r1::gentoo sys-devel/autoconf: 2.13::gentoo, 2.69-r1::gentoo sys-devel/automake: 1.11.6-r1::gentoo, 1.12.6::gentoo, 1.13.4::gentoo, 1.14.1::gentoo, 1.15::gentoo sys-devel/binutils: 2.25.1::gentoo sys-devel/gcc: 4.9.3::gentoo sys-devel/gcc-config: 1.8::gentoo sys-devel/libtool: 2.4.6-r1::gentoo sys-devel/make: 4.1-r1::gentoo sys-kernel/linux-headers: 4.1::gentoo (virtual/os-headers) sys-libs/glibc: 2.21-r1::gentoo Repositories: gentoo location: /usr/portage sync-type: rsync sync-uri: rsync://rsync.de.gentoo.org/gentoo-portage priority: -1000 overlay location: /usr/overlay masters: gentoo priority: 0 hacking-gentoo location: /var/lib/layman/hacking-gentoo masters: gentoo hacking-gentoo priority: 50 nx location: /var/lib/layman/nx masters: gentoo priority: 50 Installed sets: @kde ACCEPT_KEYWORDS="amd64 ~amd64" ACCEPT_LICENSE="* -@EULA" CBUILD="x86_64-pc-linux-gnu" CFLAGS="-march=native -mtune=native -O2 -pipe " CHOST="x86_64-pc-linux-gnu" CONFIG_PROTECT="/etc /etc/stunnel/stunnel.conf /usr/lib64/libreoffice/program/sofficerc /usr/share/config /usr/share/easy-rsa /usr/share/gnupg/qualified.txt /usr/share/maven-bin-3.0/conf /usr/share/maven-bin-3.2/conf /usr/share/themes/oxygen-gtk/gtk-2.0" CONFIG_PROTECT_MASK="/etc/ca-certificates.conf /etc/dconf /etc/env.d /etc/fonts/fonts.conf /etc/gconf /etc/gentoo-release /etc/php/apache2-php5.6/ext-active/ /etc/php/cgi-php5.6/ext-active/ /etc/php/cli-php5.6/ext-active/ /etc/revdep-rebuild /etc/sandbox.d /etc/terminfo /etc/texmf/language.dat.d /etc/texmf/language.def.d /etc/texmf/updmap.d /etc/texmf/web2c" CXXFLAGS="-march=native -mtune=native -O2 -pipe " DISTDIR="/usr/portage/distfiles" FCFLAGS="-O2 -pipe" FEATURES="assume-digests binpkg-logs clean-logs config-protect-if-modified distlocks ebuild-locks fixlafiles merge-sync metadata-transfer news parallel-fetch preserve-libs protect-owned sandbox sfperms strict unknown-features-warn unmerge-logs unmerge-orphans userfetch userpriv usersandbox usersync xattr" FFLAGS="-O2 -pipe" GENTOO_MIRRORS="http://distfiles.gentoo.org" LANG="it_IT.utf8" LDFLAGS="-Wl,-O1 -Wl,--as-needed" MAKEOPTS="-j4" PKGDIR="/usr/portage/packages" PORTAGE_CONFIGROOT="/" PORTAGE_RSYNC_OPTS="--recursive --links --safe-links --perms --times --omit-dir-times --compress --force --whole-file --delete --stats --human-readable --timeout=180 --exclude=/distfiles --exclude=/local --exclude=/packages" PORTAGE_TMPDIR="/var/tmp" USE="3dnow 3dnowext 3dnowprefetch X \ a52 aac aalib acl acpi aim alsa amd64 apng ares asf ati audio audiofile avahi bash-completion berkdb bidi bl branding bri bzip2 cairo caps ccdda cdda cdr cjk cli cracklib crypt cups curl cxx dba dbus declarative device-mapper dga divx divx4linux dparanoia dri dts dv dvb dvd dvdr dvdread eap-sim edl embedded emboss encode ethereal exif expat faad fam fame fbcon ffmpeg fftw firefox flac force-cgi-redirect fortran ftp gallium garmin gd gdbm gif gimp glamor gles2 gmedia gmp gnutls gphoto2 gpm gps gsm gtk h264 h323 iconv icq icu idn ifp ilbc imagemagick imap innodb ipod iproute2 ipv6 ithreads jabber java javascript joystick jpeg kde kipi kontact kvm lastfm lcms ldap libcaca libnotify libvirtd live lm_sensors lua lvm lxc lzma lzo mad maildir matroska mbox mdnsresponder-compat mhash mime mjpeg mmap mmx mmxext mng modules mozdevelop mozilla mp3 mp4 mpeg msn mtp multilib mysql ncurses nepomuk network networkmanager new-hpcups nfsv4 njb nls nptl nptlonly nsplugin offensive ofx ogg oggvorbis ogm openal openexr opengl openmp oscar pam pango parted pcap pcre pdf phonon php plasma plotutils png policykit ppds pulseaudio qemu qt3support qt4 qt5 readline real rtc ruby samba sasl sdl semantic-desktop session sha512 sip slang slp smartcard sndfile snmp sox speex spell srt sse sse2 ssh ssl ssse3 startup-notification svg symlink systemd tcltk tcpd theora threads tiff tk tremor truetype udev udisks unicode upower usb utempter v4l v4l2 vaapi vcd vde vhosts video videos vim-syntax virt-network virtualbox vorbis wav webkit wifi wimax wmf wmp wps wxwidgets wxwindows x264 xanim xattr xcb xcomposite xface xft xine xinerama xml xosd xpm xscreensaver xsl xulrunner xv xvid zeroconf zlib zpm" ABI_X86="64 32" ALSA_CARDS="ali5451 als4000 atiixp atiixp-modem bt87x ca0106 cmipci emu10k1x ens1370 ens1371 es1938 es1968 fm801 hda-intel intel8x0 intel8x0m maestro3 trident usb-audio via82xx via82xx-modem ymfpci" APACHE2_MODULES="authn_core authz_core socache_shmcb unixd actions alias auth_basic authn_alias authn_anon authn_dbm authn_default authn_file authz_dbm authz_default authz_groupfile authz_host authz_owner authz_user autoindex cache cgi cgid dav dav_fs dav_lock deflate dir disk_cache env expires ext_filter file_cache filter headers include info log_config logio mem_cache mime mime_magic negotiation rewrite setenvif speling status unique_id userdir usertrack vhost_alias" CALLIGRA_FEATURES="kexi words flow plan sheets stage tables krita karbon braindump author" CAMERAS="ptp2" COLLECTD_PLUGINS="df interface irq load memory rrdtool swap syslog" CPU_FLAGS_X86="aes avx mmx mmxext popcnt sse sse2 sse3 sse4_1 sse4_2 ssse3" DRACUT_MODULES="btrfs crypt crypt-gpg crypt-loop lvm plymouth systemd" ELIBC="glibc" GPSD_PROTOCOLS="ashtech aivdm earthmate evermore fv18 garmin garmintxt gpsclock itrax mtk3301 nmea ntrip navcom oceanserver oldstyle oncore rtcm104v2 rtcm104v3 sirf superstar2 timing tsip tripmate tnt ublox ubx" INPUT_DEVICES="evdev synaptics" KERNEL="linux" LCD_DEVICES="bayrad cfontz cfontz633 glk hd44780 lb216 lcdm001 mtxorb ncurses text" LIBREOFFICE_EXTENSIONS="presenter-console presenter-minimizer" LINGUAS="it en" OFFICE_IMPLEMENTATION="libreoffice" PHP_TARGETS="php5-5" PYTHON_SINGLE_TARGET="python3_4" PYTHON_TARGETS="python2_7 python3_4" QEMU_SOFTMMU_TARGETS="i386 x86_64" QEMU_USER_TARGETS="i386 x86_64" RUBY_TARGETS="ruby19 ruby20 ruby21" USERLAND="GNU" VIDEO_CARDS="intel v4l" XTABLES_ADDONS="quota2 psd pknock lscan length2 ipv4options ipset ipp2p iface geoip fuzzy condition tee tarpit sysrq steal rawnat logmark ipmark dhcpmac delude chaos account" USE_PYTHON="2.7 3.4" Unset: CPPFLAGS, CTARGET, EMERGE_DEFAULT_OPTS, INSTALL_MASK, LC_ALL, PORTAGE_BUNZIP2_COMMAND, PORTAGE_COMPRESS, PORTAGE_COMPRESS_FLAGS, PORTAGE_RSYNC_EXTRA_OPTS
(In reply to Fabio Coatti from comment #0) > Any hint about how to debug the issue will be most useful Check the logs first: ~/.cache/virt-manager/virt-manager.log
After some digging, I found maybe not the culprit but a possible good hint. If xlib-xcb use flag is active on x11-libs/cairo, several issues arise, one being this one and another is a problem in libreoffice impress with hardware acceleration activated. To solve this issue is enough, at least on my system, to turn off this flag. I can't recall why it is active on my system, probably due to having nx installed. I think I can close this bug, and maybe open another one related to cairo. Many thanks for your answer!
*** This bug has been marked as a duplicate of bug 441878 ***
