Seems to be an apparmor problem, given this kernel message:
[18863.831346] audit: type=1400 audit(1409779637.619:110): apparmor="DENIED" operation="mknod" profile="libvirt-a83f3934-2f03-4915-80fd-67130bcf234b" name="/dev/shm/spice.31266" pid=31266 comm="qemu-system-x86" requested_mask="c" denied_mask="c" fsuid=123 ouid=123
Booting with apparmor=0 fixes it.
Seems to be an apparmor problem, given this kernel message:
[18863.831346] audit: type=1400 audit(140977963 7.619:110) : apparmor="DENIED" operation="mknod" profile= "libvirt- a83f3934- 2f03-4915- 80fd-67130bcf23 4b" name="/ dev/shm/ spice.31266" pid=31266 comm="qemu- system- x86" requested_mask="c" denied_mask="c" fsuid=123 ouid=123
Booting with apparmor=0 fixes it.