linux-kernel - [PATCH V2 1/1] perf/x86: filter branches for PEBS event

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Date:	Fri, 27 Mar 2015 10:38:25 -0400
From:	kan.liang@...el.com
To:	a.p.zijlstra@...llo.nl
Cc:	eranian@...gle.com, andi@...stfloor.org,
	linux-kernel@...r.kernel.org, Kan Liang <kan.liang@...el.com>
Subject: [PATCH V2 1/1] perf/x86: filter branches for PEBS event

From: Kan Liang <kan.liang@...el.com>

For supporting Intel LBR branches filtering, Intel LBR sharing logic
mechanism is introduced from commit b36817e88630 ("perf/x86: Add Intel
LBR sharing logic"). It modifies __intel_shared_reg_get_constraints to
config lbr_sel, which is finally used to set LBR_SELECT.
However, the intel_shared_regs_constraints is called after
intel_pebs_constraints. The PEBS event will return immediately after
intel_pebs_constraints. So it's impossible to filter branches for PEBS
event.

This patch move intel_shared_regs_constraints ahead of
intel_pebs_constraints.
We can safely do that because the intel_shared_regs_constraints only
returns emptyconstraint if its rejecting the event, otherwise it returns
NULL such that we continue calling intel_pebs_constraints and
x86_get_event_constraint.

Signed-off-by: Kan Liang <kan.liang@...el.com>
---

Changes since V1:
 - Move all shared regs ahead of intel_pebs_constraints
 - Modify the description and quote Peter's comments.

 arch/x86/kernel/cpu/perf_event_intel.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index 9f1dd18..83bee99 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -1635,11 +1635,11 @@ intel_get_event_constraints(struct cpu_hw_events *cpuc, struct perf_event *event
 	if (c)
 		return c;

-	c = intel_pebs_constraints(event);
+	c = intel_shared_regs_constraints(cpuc, event);
 	if (c)
 		return c;

-	c = intel_shared_regs_constraints(cpuc, event);
+	c = intel_pebs_constraints(event);
 	if (c)
 		return c;

-- 
1.8.3.1

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