An issue was discovered in Xen through 4.11.x on Intel x86 platforms allowing guest OS users to cause a denial of service (host OS hang) because Xen does not work around Intel's mishandling of certain HLE transactions associated with the KACQUIRE instruction prefix.
https://xenbits.xen.org/xsa/advisory-282.html
https://www.debian.org/security/2019/dsa-4369
https://support.citrix.com/article/CTX239432
http://www.securityfocus.com/bid/106182
http://lists.opensuse.org/opensuse-security-announce/2019-04/msg00072.html
http://lists.opensuse.org/opensuse-security-announce/2019-04/msg00057.html