I think it is related to Apparmor, I see the following lines in /etc/syslog:
Nov 22 14:36:23 uvir kernel: [18882.602278] audit: type=1400 audit(1416663383.171:69): apparmor="DENIED" operation="open" profile="libvirt-30619811-d285-944a-026a-cdd4a753b77a" name="/sys/devices/pci0000:00/0000:00:1c.3/0000:03:00.0/usb3/uevent" pid=14279 comm="qemu-system-x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 Nov 22 14:36:23 uvir kernel: [18882.602295] audit: type=1400 audit(1416663383.171:70): apparmor="DENIED" operation="open" profile="libvirt-30619811-d285-944a-026a-cdd4a753b77a" name="/sys/devices/pci0000:00/0000:00:1c.3/0000:03:00.0/usb3/3-0:1.0/uevent" pid=14279 comm="qemu-system-x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 Nov 22 14:36:23 uvir kernel: [18882.602306] audit: type=1400 audit(1416663383.171:71): apparmor="DENIED" operation="open" profile="libvirt-30619811-d285-944a-026a-cdd4a753b77a" name="/sys/devices/pci0000:00/0000:00:1c.3/0000:03:00.0/usb4/uevent" pid=14279 comm="qemu-system-x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 Nov 22 14:36:23 uvir kernel: [18882.602318] audit: type=1400 audit(1416663383.171:72): apparmor="DENIED" operation="open" profile="libvirt-30619811-d285-944a-026a-cdd4a753b77a" name="/sys/devices/pci0000:00/0000:00:1c.3/0000:03:00.0/usb4/4-0:1.0/uevent" pid=14279 comm="qemu-system-x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 Nov 22 14:36:23 uvir kernel: [18882.602330] audit: type=1400 audit(1416663383.171:73): apparmor="DENIED" operation="open" profile="libvirt-30619811-d285-944a-026a-cdd4a753b77a" name="/sys/devices/pci0000:00/0000:00:1c.3/0000:03:00.0/usb4/4-2/uevent" pid=14279 comm="qemu-system-x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 Nov 23 00:28:39 uvir kernel: [35109.848778] audit: type=1400 audit(1416698919.255:181): apparmor="DENIED" operation="open" profile="libvirt-30619811-d285-944a-026a-cdd4a753b77a" name="/sys/devices/pci0000:00/0000:00:1c.3/0000:03:00.0/usb3/uevent" pid=25427 comm="qemu-system-x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 Nov 23 00:28:39 uvir kernel: [35109.848799] audit: type=1400 audit(1416698919.255:182): apparmor="DENIED" operation="open" profile="libvirt-30619811-d285-944a-026a-cdd4a753b77a" name="/sys/devices/pci0000:00/0000:00:1c.3/0000:03:00.0/usb3/3-0:1.0/uevent" pid=25427 comm="qemu-system-x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 Nov 23 00:28:39 uvir kernel: [35109.848815] audit: type=1400 audit(1416698919.255:183): apparmor="DENIED" operation="open" profile="libvirt-30619811-d285-944a-026a-cdd4a753b77a" name="/sys/devices/pci0000:00/0000:00:1c.3/0000:03:00.0/usb4/uevent" pid=25427 comm="qemu-system-x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 Nov 23 00:28:39 uvir kernel: [35109.848831] audit: type=1400 audit(1416698919.255:184): apparmor="DENIED" operation="open" profile="libvirt-30619811-d285-944a-026a-cdd4a753b77a" name="/sys/devices/pci0000:00/0000:00:1c.3/0000:03:00.0/usb4/4-0:1.0/uevent" pid=25427 comm="qemu-system-x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 Nov 23 00:28:39 uvir kernel: [35109.848847] audit: type=1400 audit(1416698919.255:185): apparmor="DENIED" operation="open" profile="libvirt-30619811-d285-944a-026a-cdd4a753b77a" name="/sys/devices/pci0000:00/0000:00:1c.3/0000:03:00.0/usb4/4-2/uevent" pid=25427 comm="qemu-system-x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 Nov 23 09:07:11 uvir kernel: [ 33.270565] audit: type=1400 audit(1416730031.240:59): apparmor="DENIED" operation="open" profile="libvirt-717d41d2-cfc9-5d70-e2f5-817c2ed1a90a" name="/sys/devices/pci0000:00/0000:00:1c.3/0000:03:00.0/usb3/uevent" pid=3599 comm="qemu-system-x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 Nov 23 09:07:11 uvir kernel: [ 33.270588] audit: type=1400 audit(1416730031.240:60): apparmor="DENIED" operation="open" profile="libvirt-717d41d2-cfc9-5d70-e2f5-817c2ed1a90a" name="/sys/devices/pci0000:00/0000:00:1c.3/0000:03:00.0/usb3/3-0:1.0/uevent" pid=3599 comm="qemu-system-x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 Nov 23 09:07:11 uvir kernel: [ 33.270606] audit: type=1400 audit(1416730031.240:61): apparmor="DENIED" operation="open" profile="libvirt-717d41d2-cfc9-5d70-e2f5-817c2ed1a90a" name="/sys/devices/pci0000:00/0000:00:1c.3/0000:03:00.0/usb4/uevent" pid=3599 comm="qemu-system-x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 Nov 23 09:07:11 uvir kernel: [ 33.270625] audit: type=1400 audit(1416730031.240:62): apparmor="DENIED" operation="open" profile="libvirt-717d41d2-cfc9-5d70-e2f5-817c2ed1a90a" name="/sys/devices/pci0000:00/0000:00:1c.3/0000:03:00.0/usb4/4-0:1.0/uevent" pid=3599 comm="qemu-system-x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0
I think it is related to Apparmor, I see the following lines in /etc/syslog:
Nov 22 14:36:23 uvir kernel: [18882.602278] audit: type=1400 audit(141666338 3.171:69) : apparmor="DENIED" operation="open" profile= "libvirt- 30619811- d285-944a- 026a-cdd4a753b7 7a" name="/ sys/devices/ pci0000: 00/0000: 00:1c.3/ 0000:03: 00.0/usb3/ uevent" pid=14279 comm="qemu- system- x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 3.171:70) : apparmor="DENIED" operation="open" profile= "libvirt- 30619811- d285-944a- 026a-cdd4a753b7 7a" name="/ sys/devices/ pci0000: 00/0000: 00:1c.3/ 0000:03: 00.0/usb3/ 3-0:1.0/ uevent" pid=14279 comm="qemu- system- x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 3.171:71) : apparmor="DENIED" operation="open" profile= "libvirt- 30619811- d285-944a- 026a-cdd4a753b7 7a" name="/ sys/devices/ pci0000: 00/0000: 00:1c.3/ 0000:03: 00.0/usb4/ uevent" pid=14279 comm="qemu- system- x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 3.171:72) : apparmor="DENIED" operation="open" profile= "libvirt- 30619811- d285-944a- 026a-cdd4a753b7 7a" name="/ sys/devices/ pci0000: 00/0000: 00:1c.3/ 0000:03: 00.0/usb4/ 4-0:1.0/ uevent" pid=14279 comm="qemu- system- x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 3.171:73) : apparmor="DENIED" operation="open" profile= "libvirt- 30619811- d285-944a- 026a-cdd4a753b7 7a" name="/ sys/devices/ pci0000: 00/0000: 00:1c.3/ 0000:03: 00.0/usb4/ 4-2/uevent" pid=14279 comm="qemu- system- x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 9.255:181) : apparmor="DENIED" operation="open" profile= "libvirt- 30619811- d285-944a- 026a-cdd4a753b7 7a" name="/ sys/devices/ pci0000: 00/0000: 00:1c.3/ 0000:03: 00.0/usb3/ uevent" pid=25427 comm="qemu- system- x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 9.255:182) : apparmor="DENIED" operation="open" profile= "libvirt- 30619811- d285-944a- 026a-cdd4a753b7 7a" name="/ sys/devices/ pci0000: 00/0000: 00:1c.3/ 0000:03: 00.0/usb3/ 3-0:1.0/ uevent" pid=25427 comm="qemu- system- x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 9.255:183) : apparmor="DENIED" operation="open" profile= "libvirt- 30619811- d285-944a- 026a-cdd4a753b7 7a" name="/ sys/devices/ pci0000: 00/0000: 00:1c.3/ 0000:03: 00.0/usb4/ uevent" pid=25427 comm="qemu- system- x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 9.255:184) : apparmor="DENIED" operation="open" profile= "libvirt- 30619811- d285-944a- 026a-cdd4a753b7 7a" name="/ sys/devices/ pci0000: 00/0000: 00:1c.3/ 0000:03: 00.0/usb4/ 4-0:1.0/ uevent" pid=25427 comm="qemu- system- x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 9.255:185) : apparmor="DENIED" operation="open" profile= "libvirt- 30619811- d285-944a- 026a-cdd4a753b7 7a" name="/ sys/devices/ pci0000: 00/0000: 00:1c.3/ 0000:03: 00.0/usb4/ 4-2/uevent" pid=25427 comm="qemu- system- x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 1.240:59) : apparmor="DENIED" operation="open" profile= "libvirt- 717d41d2- cfc9-5d70- e2f5-817c2ed1a9 0a" name="/ sys/devices/ pci0000: 00/0000: 00:1c.3/ 0000:03: 00.0/usb3/ uevent" pid=3599 comm="qemu- system- x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 1.240:60) : apparmor="DENIED" operation="open" profile= "libvirt- 717d41d2- cfc9-5d70- e2f5-817c2ed1a9 0a" name="/ sys/devices/ pci0000: 00/0000: 00:1c.3/ 0000:03: 00.0/usb3/ 3-0:1.0/ uevent" pid=3599 comm="qemu- system- x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 1.240:61) : apparmor="DENIED" operation="open" profile= "libvirt- 717d41d2- cfc9-5d70- e2f5-817c2ed1a9 0a" name="/ sys/devices/ pci0000: 00/0000: 00:1c.3/ 0000:03: 00.0/usb4/ uevent" pid=3599 comm="qemu- system- x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0 1.240:62) : apparmor="DENIED" operation="open" profile= "libvirt- 717d41d2- cfc9-5d70- e2f5-817c2ed1a9 0a" name="/ sys/devices/ pci0000: 00/0000: 00:1c.3/ 0000:03: 00.0/usb4/ 4-0:1.0/ uevent" pid=3599 comm="qemu- system- x86" requested_mask="r" denied_mask="r" fsuid=106 ouid=0
Nov 22 14:36:23 uvir kernel: [18882.602295] audit: type=1400 audit(141666338
Nov 22 14:36:23 uvir kernel: [18882.602306] audit: type=1400 audit(141666338
Nov 22 14:36:23 uvir kernel: [18882.602318] audit: type=1400 audit(141666338
Nov 22 14:36:23 uvir kernel: [18882.602330] audit: type=1400 audit(141666338
Nov 23 00:28:39 uvir kernel: [35109.848778] audit: type=1400 audit(141669891
Nov 23 00:28:39 uvir kernel: [35109.848799] audit: type=1400 audit(141669891
Nov 23 00:28:39 uvir kernel: [35109.848815] audit: type=1400 audit(141669891
Nov 23 00:28:39 uvir kernel: [35109.848831] audit: type=1400 audit(141669891
Nov 23 00:28:39 uvir kernel: [35109.848847] audit: type=1400 audit(141669891
Nov 23 09:07:11 uvir kernel: [ 33.270565] audit: type=1400 audit(141673003
Nov 23 09:07:11 uvir kernel: [ 33.270588] audit: type=1400 audit(141673003
Nov 23 09:07:11 uvir kernel: [ 33.270606] audit: type=1400 audit(141673003
Nov 23 09:07:11 uvir kernel: [ 33.270625] audit: type=1400 audit(141673003