Re: [PATCH v6 04/11] powerpc/perf: Add event attribute and group to IMC pmus

From: Daniel Axtens <hidden>
Date: 2017-04-04 02:11:32
Also in: lkml

Hi,

quoted hunk ↗ jump to hunk

Device tree IMC driver code parses the IMC units and their events. It
passes the information to IMC pmu code which is placed in powerpc/perf
as "imc-pmu.c".

This patch creates only event attributes and attribute groups for the
IMC pmus.

Signed-off-by: Anju T Sudhakar <redacted>
Signed-off-by: Hemant Kumar <redacted>
Signed-off-by: Madhavan Srinivasan <redacted>
---
 arch/powerpc/perf/Makefile                |  6 +-
 arch/powerpc/perf/imc-pmu.c               | 97 +++++++++++++++++++++++++++++++
 arch/powerpc/platforms/powernv/opal-imc.c | 12 +++-
 3 files changed, 112 insertions(+), 3 deletions(-)
 create mode 100644 arch/powerpc/perf/imc-pmu.c

diff --git a/arch/powerpc/perf/Makefile b/arch/powerpc/perf/Makefile
index 4d606b99a5cb..d0d1f04203c7 100644
--- a/arch/powerpc/perf/Makefile
+++ b/arch/powerpc/perf/Makefile

@@ -2,10 +2,14 @@ subdir-ccflags-$(CONFIG_PPC_WERROR) := -Werror
 
 obj-$(CONFIG_PERF_EVENTS)	+= callchain.o perf_regs.o
 
+imc-$(CONFIG_PPC_POWERNV)       += imc-pmu.o
+
 obj-$(CONFIG_PPC_PERF_CTRS)	+= core-book3s.o bhrb.o
 obj64-$(CONFIG_PPC_PERF_CTRS)	+= power4-pmu.o ppc970-pmu.o power5-pmu.o \
 				   power5+-pmu.o power6-pmu.o power7-pmu.o \
-				   isa207-common.o power8-pmu.o power9-pmu.o
+				   isa207-common.o power8-pmu.o power9-pmu.o \
+				   $(imc-y)

Hmm, this seems... obtuse. Will the IMC stuff fail to compile on
non-powerNV? Can we just link it in like we do with every other sort of
performance counter and let runtime detection do its thing?

quoted hunk ↗ jump to hunk

+
 obj32-$(CONFIG_PPC_PERF_CTRS)	+= mpc7450-pmu.o
 
 obj-$(CONFIG_FSL_EMB_PERF_EVENT) += core-fsl-emb.o

diff --git a/arch/powerpc/perf/imc-pmu.c b/arch/powerpc/perf/imc-pmu.c
new file mode 100644
index 000000000000..ec464c76b749
--- /dev/null
+++ b/arch/powerpc/perf/imc-pmu.c

@@ -0,0 +1,97 @@
+/*
+ * Nest Performance Monitor counter support.
+ *
+ * Copyright (C) 2016 Madhavan Srinivasan, IBM Corporation.
+ *	     (C) 2016 Hemant K Shaw, IBM Corporation.
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
+ * by the Free Software Foundation.
+ */
+#include <linux/perf_event.h>
+#include <linux/slab.h>
+#include <asm/opal.h>
+#include <asm/imc-pmu.h>
+#include <asm/cputhreads.h>
+#include <asm/smp.h>
+#include <linux/string.h>
+
+struct perchip_nest_info nest_perchip_info[IMC_MAX_CHIPS];
+struct imc_pmu *per_nest_pmu_arr[IMC_MAX_PMUS];
+
+/* dev_str_attr : Populate event "name" and string "str" in attribute */
+static struct attribute *dev_str_attr(const char *name, const char *str)
+{
+	struct perf_pmu_events_attr *attr;
+
+	attr = kzalloc(sizeof(*attr), GFP_KERNEL);
+
+	sysfs_attr_init(&attr->attr.attr);
+
+	attr->event_str = str;
+	attr->attr.attr.name = name;
+	attr->attr.attr.mode = 0444;
+	attr->attr.show = perf_event_sysfs_show;
+
+	return &attr->attr.attr;
+}
+
+/*
+ * update_events_in_group: Update the "events" information in an attr_group
+ *                         and assign the attr_group to the pmu "pmu".
+ */
+static int update_events_in_group(struct imc_events *events,
+				  int idx, struct imc_pmu *pmu)

So I've probably missed a key point in the earlier patches, but for the
life of me I cannot figure out what idx is supposed to represent.

+{
+	struct attribute_group *attr_group;
+	struct attribute **attrs;
+	int i;
+
+	/* Allocate memory for attribute group */
+	attr_group = kzalloc(sizeof(*attr_group), GFP_KERNEL);
+	if (!attr_group)
+		return -ENOMEM;
+
+	/* Allocate memory for attributes */
+	attrs = kzalloc((sizeof(struct attribute *) * (idx + 1)), GFP_KERNEL);

Also, idx is an int, so:
 - things will go wrong if idx is -1
 - things will go very wrong if idx is -2
 - do you need to do some sort of validation to make sure it's within
   bounds? If not in this function, what function ensures the necessary
   'sanity check' preconditions for idx?

+	if (!attrs) {
+		kfree(attr_group);
+		return -ENOMEM;
+	}
+
+	attr_group->name = "events";
+	attr_group->attrs = attrs;
+	for (i = 0; i < idx; i++, events++) {
+		attrs[i] = dev_str_attr((char *)events->ev_name,
+					(char *)events->ev_value);
+	}
+
+	pmu->attr_groups[0] = attr_group;

Again, I may have missed something, but what's special about group 0?
Patch 1 lets you have up to 4 groups - are they used elsewhere?

+	return 0;
+}
+
+/*
+ * init_imc_pmu : Setup the IMC pmu device in "pmu_ptr" and its events
+ *                "events".
+ * Setup the cpu mask information for these pmus and setup the state machine
+ * hotplug notifiers as well.

I cannot figure out how this function sets cpu mask information or sets
up hotplug notifiers. Is this done in a later patch? (looking at the
subject lines - perhaps patch 6?)

+ */
+int init_imc_pmu(struct imc_events *events, int idx,
+		 struct imc_pmu *pmu_ptr)

Should this be marked __init, or can it be called in a hotplug path?

quoted hunk ↗ jump to hunk

+{
+	int ret = -ENODEV;
+
+	ret = update_events_in_group(events, idx, pmu_ptr);
+	if (ret)
+		goto err_free;
+
+	return 0;
+
+err_free:
+	/* Only free the attr_groups which are dynamically allocated  */
+	if (pmu_ptr->attr_groups[0]) {
+		kfree(pmu_ptr->attr_groups[0]->attrs);
+		kfree(pmu_ptr->attr_groups[0]);
+	}
+
+	return ret;
+}

diff --git a/arch/powerpc/platforms/powernv/opal-imc.c b/arch/powerpc/platforms/powernv/opal-imc.c
index ba0203e669c0..73c46703c2af 100644
--- a/arch/powerpc/platforms/powernv/opal-imc.c
+++ b/arch/powerpc/platforms/powernv/opal-imc.c

@@ -32,8 +32,11 @@
 #include <asm/cputable.h>
 #include <asm/imc-pmu.h>
 
-struct perchip_nest_info nest_perchip_info[IMC_MAX_CHIPS];
-struct imc_pmu *per_nest_pmu_arr[IMC_MAX_PMUS];
+extern struct perchip_nest_info nest_perchip_info[IMC_MAX_CHIPS];
+extern struct imc_pmu *per_nest_pmu_arr[IMC_MAX_PMUS];

Why are these definitions being moved?
If they're still needed in this file, should the extern lines live in a
header file?

quoted hunk ↗ jump to hunk

+
+extern int init_imc_pmu(struct imc_events *events,
+			int idx, struct imc_pmu *pmu_ptr);
 
 static int imc_event_info(char *name, struct imc_events *events)
 {

@@ -379,6 +382,11 @@ static int imc_pmu_create(struct device_node *parent, int pmu_index)
 		idx += ret;
 	}
 
+	ret = init_imc_pmu(events, idx, pmu_ptr);
+	if (ret) {
+		pr_err("IMC PMU %s Register failed\n", pmu_ptr->pmu.name);
+		goto free_events;
+	}
 	return 0;
 
 free_events:

-- 
2.7.4

Regards,
Daniel

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