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Commit 24223657 authored by Venkatesh Srinivas's avatar Venkatesh Srinivas Committed by Ingo Molnar
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perf/x86/intel: Use rdmsrl_safe() when initializing RAPL PMU 



CPUs which should support the RAPL counters according to
Family/Model/Stepping may still issue #GP when attempting to access
the RAPL MSRs. This may happen when Linux is running under KVM and
we are passing-through host F/M/S data, for example. Use rdmsrl_safe
to first access the RAPL_POWER_UNIT MSR; if this fails, do not
attempt to use this PMU.

Signed-off-by: default avatarVenkatesh Srinivas <venkateshs@google.com>
Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1394739386-22260-1-git-send-email-venkateshs@google.com


Cc: zheng.z.yan@intel.com
Cc: eranian@google.com
Cc: ak@linux.intel.com
Cc: linux-kernel@vger.kernel.org
[ The patch also silently fixes another bug: rapl_pmu_init() didn't handle the memory alloc failure case previously. ]
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 6381c24c

arch/x86/kernel/cpu/perf_event_intel_rapl.c

+9 −3
Original line number Diff line number Diff line
@@ -535,6 +535,7 @@ static int rapl_cpu_prepare(int cpu) 
	struct rapl_pmu *pmu = per_cpu(rapl_pmu, cpu);

	int phys_id = topology_physical_package_id(cpu);

	u64 ms;

	u64 msr_rapl_power_unit_bits;



	if (pmu)

		return 0;
@@ -542,6 +543,9 @@ static int rapl_cpu_prepare(int cpu) 
	if (phys_id < 0)

		return -1;



	if (!rdmsrl_safe(MSR_RAPL_POWER_UNIT, &msr_rapl_power_unit_bits))

		return -1;



	pmu = kzalloc_node(sizeof(*pmu), GFP_KERNEL, cpu_to_node(cpu));

	if (!pmu)

		return -1;
@@ -555,8 +559,7 @@ static int rapl_cpu_prepare(int cpu) 
	 *

	 * we cache in local PMU instance

	 */

	rdmsrl(MSR_RAPL_POWER_UNIT, pmu->hw_unit);

	pmu->hw_unit = (pmu->hw_unit >> 8) & 0x1FULL;

	pmu->hw_unit = (msr_rapl_power_unit_bits >> 8) & 0x1FULL;

	pmu->pmu = &rapl_pmu_class;



	/*
@@ -677,7 +680,9 @@ static int __init rapl_pmu_init(void) 
	cpu_notifier_register_begin();



	for_each_online_cpu(cpu) {

		rapl_cpu_prepare(cpu);

		ret = rapl_cpu_prepare(cpu);

		if (ret)

			goto out;

		rapl_cpu_init(cpu);

	}
@@ -700,6 +705,7 @@ static int __init rapl_pmu_init(void) 
		hweight32(rapl_cntr_mask),

		ktime_to_ms(pmu->timer_interval));



out:

	cpu_notifier_register_done();



	return 0;