Filter MSR writes from user-space by default, and print a syslog entry if they happen outside the allowed set of MSRs, which is a single one for now, MSR_IA32_ENERGY_PERF_BIAS. The plan is to eventually disable MSR writes by default (they can still be enabled via allow_writes=on). Signed-off-by: Ingo Molnar <mingo@kernel.org>