[PATCH 3.15 47/84] intel_pstate: Set CPU number before accessing MSRs

From: Greg Kroah-Hartman
Date: Tue Jul 15 2014 - 19:16:08 EST

3.15-stable review patch. If anyone has any objections, please let me know.


From: Vincent Minet <vincent@xxxxxxxxxxxxxxxxx>

commit 179e8471673ce0249cd4ecda796008f7757e5bad 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@xxxxxxxxxxxxxxxxx>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

drivers/cpufreq/intel_pstate.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -709,9 +709,8 @@ static int intel_pstate_init_cpu(unsigne

cpu = all_cpu_data[cpunum];

- intel_pstate_get_cpu_pstates(cpu);
cpu->cpu = cpunum;
+ intel_pstate_get_cpu_pstates(cpu);

cpu->timer.function = intel_pstate_timer_func;

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