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Date:   Tue, 04 Apr 2017 12:11:25 +1000
From:   Daniel Axtens <dja@...ens.net>
To:     Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>, mpe@...erman.id.au
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        ego@...ux.vnet.ibm.com, bsingharora@...il.com,
        benh@...nel.crashing.org, paulus@...ba.org, anton@...ba.org,
        sukadev@...ux.vnet.ibm.com, mikey@...ling.org,
        stewart@...ux.vnet.ibm.com, eranian@...gle.com,
        Hemant Kumar <hemant@...ux.vnet.ibm.com>,
        Anju T Sudhakar <anju@...ux.vnet.ibm.com>,
        Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>
Subject: Re: [PATCH v6 04/11] powerpc/perf: Add event attribute and group to IMC pmus

Hi,

> 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 <anju@...ux.vnet.ibm.com>
> Signed-off-by: Hemant Kumar <hemant@...ux.vnet.ibm.com>
> Signed-off-by: Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>
> ---
>  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?

> +
>  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?

> +{
> +	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?

> +
> +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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