[gentoo-hardened] Problem with usb-passthrough using libvirt with hardened-sources-3.15.8

[Marcin Mirosław]

Hi!
A few days ago I boot KVM host with hardened kernel. After some time I
noticed that usb passthrough from host to kvm guest doesn't work. Simply
sayoing guest didn't seen any usb device. After switching kernel on host
to gentoo-sources-{3.14.14,3.16.2} usb-passthrough works as I expect. I
didn't any related information in logs.
Does libvirt or grsec need special configuration to have such feature
working?
Thanks,
Marcin