linux-kernel - [PATCH v2] perf: honoring the architectural performance monitoring version

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Date:	Fri,  5 Jun 2015 17:28:45 +0200
From:	Imre Palik <imrep.amz@...il.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Paul Mackerras <paulus@...ba.org>, Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, "Palik, Imre" <imrep@...zon.de>,
	Anthony Liguori <aliguori@...zon.com>
Subject: [PATCH v2] perf: honoring the architectural performance monitoring version

From: "Palik, Imre" <imrep@...zon.de>

Architectural performance monitoring version 1 doesn't support fixed
counters.  Currently, even if a hypervisor advertises support for
architectural performance monitoring version 1, perf may still tries to use
the fixed counters, as the constraints are set up based on the CPU model.

This patch ensures that perf honors the architectural performance
monitoring version returned by CPUID, and it only uses the fixed counters
for version two and above.

Some of the ideas in this patch are coming from Peter Zijlstra.

Signed-off-by: Imre Palik <imrep@...zon.de>
Cc: Anthony Liguori <aliguori@...zon.com>
---
 arch/x86/kernel/cpu/perf_event_intel.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index 3998131..bde66aa 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -1870,7 +1870,7 @@ x86_get_event_constraints(struct cpu_hw_events *cpuc, int idx,
 		for_each_event_constraint(c, x86_pmu.event_constraints) {
 			if ((event->hw.config & c->cmask) == c->code) {
 				event->hw.flags |= c->flags;
-				return c;
+				return  c->idxmsk64 ? c : NULL;
 			}
 		}
 	}
@@ -3341,9 +3341,12 @@ __init int intel_pmu_init(void)
 		for_each_event_constraint(c, x86_pmu.event_constraints) {
 			if (c->cmask != FIXED_EVENT_FLAGS
 			    || c->idxmsk64 == INTEL_PMC_MSK_FIXED_REF_CYCLES) {
+				c->idxmsk64 &=
+					~(~0UL << (INTEL_PMC_IDX_FIXED + x86_pmu.num_counters_fixed));
 				continue;
 			}
-
+			c->idxmsk64 &=
+				~(~0UL << (INTEL_PMC_IDX_FIXED + x86_pmu.num_counters_fixed));
 			c->idxmsk64 |= (1ULL << x86_pmu.num_counters) - 1;
 			c->weight += x86_pmu.num_counters;
 		}
-- 
1.7.9.5

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