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

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Message-Id: <20140715231714.623077138@linuxfoundation.org>
Date:	Tue, 15 Jul 2014 16:17:44 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Vincent Minet <vincent@...cent-minet.net>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>
Subject: [PATCH 3.15 47/84] intel_pstate: Set CPU number before accessing MSRs

3.15-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>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 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);

 	init_timer_deferrable(&cpu->timer);
 	cpu->timer.function = intel_pstate_timer_func;

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