This update for kvm fixes one security issues. This security issue was fixed: - CVE-2018-3639: Spectre v4 vulnerability mitigation support for KVM guests . Systems with microprocessors utilizing speculative execution and speculative execution of memory reads before the addresses of all prior memory writes are known may allow unauthorized disclosure of information to an attacker with local user access via a side-channel analysis. This patch permits the new x86 cpu feature flag named ssbd to be presented to the guest, given that the host has this feature, and KVM exposes it to the guest as well. For this feature to be enabled please use the qemu commandline -cpu $MODEL,+spec-ctrl,+ssbd so the guest OS can take advantage of the feature. spec-ctrl and ssbd support is also required in the host.