guest use of HLE constructs may lock up host

ISSUE DESCRIPTION

Various Intel CPU models have an erratum listed under the title “Processor May Hang When Executing Code In an HLE Transaction”. It describes a potential hang when using instructions with the XACQUIRE prefix on the host physical memory range covering the first 4 MiB starting at the 1GiB boundary.

IMPACT

A malicious or buggy guest may cause a CPU to hang, resulting in a DoS (Denial of Service) affecting the entire host.

VULNERABLE SYSTEMS

All Xen versions are affected.
Only Intel based x86 systems are affected. Please refer to Intel documentation as to which specific CPU models are affected.
AMD x86 systems as well as Arm ones are not affected.