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>

1 files 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 4b9a9e9466bd..7c87424d4140 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;