This update for xen fixes the following issues:
Security issues fixed:
CVE-2018-3639: Spectre V4 – Speculative Store Bypass aka 'Memory Disambiguation' (bsc#1092631)
This feature can be controlled by the 'ssbd=on/off' commandline flag for the XEN hypervisor.
CVE-2018-10982: x86 vHPET interrupt injection errors (XSA-261 bsc#1090822)
CVE-2018-10981: qemu may drive Xen into unbounded loop (XSA-262 bsc#1090823)
Other bugfixes: