[tip:perf/core] perf/x86/intel: Use rdmsrl_safe() when initializing RAPL PMU

tip-bot for Venkatesh Srinivas
2014-04-18T13:09:09Z

Commit-ID: 24223657806a0ebd0ae5c9caaf7b021091889cf2
Gitweb: http://git.kernel.org/tip/24223657806a0ebd0ae5c9caaf7b021091889cf2
Author: Venkatesh Srinivas <venkateshs@google.com>
AuthorDate: Thu, 13 Mar 2014 12:36:26 -0700
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 18 Apr 2014 12:14:26 +0200

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: Venkatesh Srinivas <venkateshs@google.com>
Signed-off-by: Peter 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: Ingo Molnar <mingo@kernel.org>
---
arch/x86/kernel/cpu/perf_event_intel_rapl.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel_rapl.c b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
index 4b9a9e9..7c87424 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_rapl.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
@@ -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;