An issue was discovered in Xen 4.4.x through 4.9.x allowing ARM guest OS users to cause a denial of service (prevent physical CPU usage) because of lock mishandling upon detection of an add-to-physmap error.
https://xenbits.xen.org/xsa/advisory-235.html
http://www.securitytracker.com/id/1039568
http://www.debian.org/security/2017/dsa-3969