Xen 4.5.x through 4.7.x on AMD systems without the NRip feature, when emulating instructions that generate software interrupts, allows local HVM guest OS users to cause a denial of service (guest crash) by leveraging an incorrect choice for software interrupt delivery.
https://security.gentoo.org/glsa/201612-56
http://xenbits.xen.org/xsa/advisory-196.html