linux-kernel - [PATCH 3.13 073/259] intel_pstate: Set CPU number before accessing MSRs

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Date:	Fri,  8 Aug 2014 13:38:16 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Vincent Minet <vincent@...cent-minet.net>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.13 073/259] intel_pstate: Set CPU number before accessing MSRs

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

------------------

From: Vincent Minet <vincent@...cent-minet.net>

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@...cent-minet.net>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
[ kamal: backport to 3.13-stable (context) ]
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 drivers/cpufreq/intel_pstate.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index fbfdde1..2d26563 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/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 =
-- 
1.9.1

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