The vgic_v2_to_sgi function in arch/arm/vgic-v2.c in Xen 4.5.x, when running on ARM hardware with general interrupt controller (GIC) version 2, allows local guest users to cause a denial of service (host crash) by writing an invalid value to the GICD.SGIR register.
https://exchange.xforce.ibmcloud.com/vulnerabilities/100868
http://xenbits.xen.org/xsa/advisory-117.html