Red Hat: RHSA-2018:1997-01 Important: libvirt Cache Breach Fix

The libvirt library contains a C API for managing and interacting with the virtualization capabilities of Linux and other operating systems. In addition, libvirt provides tools for remote management of virtualized systems.
Security Fix(es):
* An industry-wide issue was found in the way many modern microprocessor designs have implemented speculative execution of Load & Store instructions (a commonly used performance optimization). It relies on the presence of a precisely-defined instruction sequence in the privileged code as well as the fact that memory read from address to which a recent memory write has occurred may see an older value and subsequently cause an update into the microprocessor's data cache even for speculatively executed instructions that never actually commit (retire). As a result, an unprivileged attacker could use this flaw to read privileged memory by conducting targeted cache side-channel attacks. (CVE-2018-3639)
Note: This is the libvirt side of the CVE-2018-3639 mitigation that includes support for guests running on hosts with AMD processors.
Red Hat would like to thank Ken Johnson (Microsoft Security Response Center) and Jann Horn (Google Project Zero) for reporting this issue.
Bug Fix(es):
* Previously, the virtlogd service logged redundant AVC denial errors when a guest virtual machine was started. With this update, the virtlogd service no longer attempts to send shutdown inhibition calls to systemd, which prevents the described errors from occurring. (BZ#1573268)
* Prior to this update, guest virtual machine actions that use a python library in some cases failed and "Hash operation not allowed during iteration" error messages were logged. Several redundant thread access checks have been removed, and the problem no longer occurs. (BZ#1581364)
* The "virsh capabilities" command previously displayed an inaccurate number of 4 KiB memory pages on systems with very large amounts of memory. This update optimizes the memory diagnostic mechanism to ensure memory page numbers are displayed correctly on such systems. (BZ#1582418)