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

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Date:	Thu, 26 Mar 2015 14:13:23 -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 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 for branch_reg ahead of
intel_pebs_constraints.
intel_shared_regs_constraints for branch_reg doesn't modify event->hw,
so it's safe to be called before intel_pebs_constraints.
intel_shared_regs_constraints for branch_reg also special case when it
returns &emptyconstraint. It put constraints for extra_reg. This patch
remove it. Because it will never get constraints for extra_reg if return
is &emptyconstraint.

Signed-off-by: Kan Liang <kan.liang@...el.com>
---
 arch/x86/kernel/cpu/perf_event_intel.c | 34 ++++++++++++----------------------
 1 file changed, 12 insertions(+), 22 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index 9f1dd18..247780a 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -1587,25 +1587,14 @@ __intel_shared_reg_put_constraints(struct cpu_hw_events *cpuc,
 
 static struct event_constraint *
 intel_shared_regs_constraints(struct cpu_hw_events *cpuc,
-			      struct perf_event *event)
+			      struct perf_event *event,
+			      struct hw_perf_event_extra *reg)
 {
-	struct event_constraint *c = NULL, *d;
-	struct hw_perf_event_extra *xreg, *breg;
+	struct event_constraint *c = NULL;
+
+	if (reg->idx != EXTRA_REG_NONE)
+		c = __intel_shared_reg_get_constraints(cpuc, event, reg);
 
-	xreg = &event->hw.extra_reg;
-	if (xreg->idx != EXTRA_REG_NONE) {
-		c = __intel_shared_reg_get_constraints(cpuc, event, xreg);
-		if (c == &emptyconstraint)
-			return c;
-	}
-	breg = &event->hw.branch_reg;
-	if (breg->idx != EXTRA_REG_NONE) {
-		d = __intel_shared_reg_get_constraints(cpuc, event, breg);
-		if (d == &emptyconstraint) {
-			__intel_shared_reg_put_constraints(cpuc, xreg);
-			c = d;
-		}
-	}
 	return c;
 }
 
@@ -1629,17 +1618,18 @@ x86_get_event_constraints(struct cpu_hw_events *cpuc, struct perf_event *event)
 static struct event_constraint *
 intel_get_event_constraints(struct cpu_hw_events *cpuc, struct perf_event *event)
 {
-	struct event_constraint *c;
+	struct event_constraint *c, *d;
 
 	c = intel_bts_constraints(event);
 	if (c)
 		return c;
 
-	c = intel_pebs_constraints(event);
-	if (c)
-		return c;
+	c = intel_shared_regs_constraints(cpuc, event, &event->hw.branch_reg);
+	d = intel_pebs_constraints(event);
+	if (d || c)
+		return (d) ? (d) : (c);
 
-	c = intel_shared_regs_constraints(cpuc, event);
+	c = intel_shared_regs_constraints(cpuc, event, &event->hw.extra_reg);
 	if (c)
 		return c;
 
-- 
1.8.3.2

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