intel_pstate: Set CPU number before accessing MSRs

commit 179e8471 upstream.

Ensure that cpu->cpu is set before writing MSR_IA32_PERF_CTL during CPU
initialization. Otherwise only cpu0 has its P-state set and all other
cores are left with their values unchanged.

In most cases, this is not too serious because the P-states will be set
correctly when the timer function is run.  But when the default governor
is set to performance, the per-CPU current_pstate stays the same forever
and no attempts are made to write the MSRs again.
Signed-off-by: Vincent Minet <vincent@vincent-minet.net>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
[ kamal: backport to 3.13-stable (context) ]
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/cpufreq/intel_pstate.c

@@ -685,6 +685,7 @@ static int intel_pstate_init_cpu(unsigned int cpunum)
 
 	cpu = all_cpu_data[cpunum];
 
+	cpu->cpu = cpunum;
 	intel_pstate_get_cpu_pstates(cpu);
 	if (!cpu->pstate.current_pstate) {
 		all_cpu_data[cpunum] = NULL;
@@ -692,8 +693,6 @@ static int intel_pstate_init_cpu(unsigned int cpunum)
 		return -ENODATA;
 	}
 
-	cpu->cpu = cpunum;
-
 	init_timer_deferrable(&cpu->timer);
 	cpu->timer.function = intel_pstate_timer_func;
 	cpu->timer.data =