Xen guests cannot make use of all CPU features, and in some cases they are even risky to be advertised. One such feature is CONSTANT_TSC. This feature prevents the TSC (Time Stamp Counter) from being marked as unstable, which allows the sched_clock_stable option to be enabled. Having the sched_clock_stable option enabled is problematic for Xen PV guests because the sched_clock() function has been overridden with the xen_sched_clock() function, which is not synchronized between virtual CPUs. This update provides a patch, which sets all x86_power features to 0 as a preventive measure against other potentially dangerous assumptions the kernel could make based on the features, fixing this issue.