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From: Stephane Eranian <eranian@google.com>
To: linux-kernel@vger.kernel.org
Cc: peterz@infradead.org, mingo@elte.hu, venkateshs@google.com,
	bp@alien8.de, ak@linux.intel.com, zheng.z.yan@intel.com
Subject: [PATCH] perf/x86: fix RAPL rdmsrl_safe() usage
Date: Wed, 23 Apr 2014 19:04:19 +0200	[thread overview]
Message-ID: <20140423170418.GA12767@quad> (raw)


This patch fixes a bug introduced by commit 24223657.

The rdmsrl_safe() function returns 0 on success.
The current code was failing to detect the RAPL PMU
on real hardware  (missing /sys/devices/power) because
the return value of rdmsrl_safe() was misinterpreted.

Signed-off-by: Stephane Eranian <eranian@google.com>

diff --git a/arch/x86/kernel/cpu/perf_event_intel_rapl.c b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
index 7c87424..619f769 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_rapl.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
@@ -543,7 +543,8 @@ 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))
+	/* protect rdmsrl() to handle virtualization */
+	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));

             reply	other threads:[~2014-04-23 17:04 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-04-23 17:04 Stephane Eranian [this message]
2014-04-23 19:00 ` [PATCH] perf/x86: fix RAPL rdmsrl_safe() usage Borislav Petkov
2014-04-23 19:27   ` Venkatesh Srinivas
2014-04-23 20:00     ` Andi Kleen
2014-04-24  8:03 ` [tip:perf/urgent] perf/x86: Fix " tip-bot for Stephane Eranian

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