RE: [PATCH v3 3/4] perf: imx_perf: limit counter ID from user space and optimize counter usage

[Frank Li]

> -----Original Message-----
> From: Xu Yang <xu.yang_2@xxxxxxx>
> Sent: Monday, January 29, 2024 4:15 AM
> To: Frank Li <frank.li@xxxxxxx>; will@xxxxxxxxxx; mark.rutland@xxxxxxx;
> robh+dt@xxxxxxxxxx; krzysztof.kozlowski+dt@xxxxxxxxxx;
> conor+dt@xxxxxxxxxx; shawnguo@xxxxxxxxxx; s.hauer@xxxxxxxxxxxxxx;
> kernel@xxxxxxxxxxxxxx; festevam@xxxxxxxxx; john.g.garry@xxxxxxxxxx;
> jolsa@xxxxxxxxxx; namhyung@xxxxxxxxxx; irogers@xxxxxxxxxx
> Cc: dl-linux-imx <linux-imx@xxxxxxx>; mike.leach@xxxxxxxxxx;
> leo.yan@xxxxxxxxxx; peterz@xxxxxxxxxxxxx; mingo@xxxxxxxxxx;
> acme@xxxxxxxxxx; alexander.shishkin@xxxxxxxxxxxxxxx;
> adrian.hunter@xxxxxxxxx; Xu Yang <xu.yang_2@xxxxxxx>; linux-arm-
> kernel@xxxxxxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; linux-perf-users@xxxxxxxxxxxxxxx
> Subject: [PATCH v3 3/4] perf: imx_perf: limit counter ID from user space and
> optimize counter usage
> 
> The user can pass any counter ID to perf app. However, current pmu driver
> doesn't judge the validity of the counter ID. This will add necessary
> check for counter ID from user space. Besides, this pmu has 10 counters
> except cycle counter which can be used to count reference events and
> counter specific evnets. This will also add supports to auto allocate
> counter if the user doesn't pass it the perf. Then, the usage of counter
> will be optimized.
> 
> Signed-off-by: Xu Yang <xu.yang_2@xxxxxxx>
> 
> ---
> Changes in v2:
>  - limit counter ID from user to 0-10
>  - combine dynamic and static allocation of counter
> Changes in v3:
>  - no changes
> ---
>  drivers/perf/fsl_imx9_ddr_perf.c | 69
> +++++++++++++++++++++++++++++++-
>  1 file changed, 67 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/perf/fsl_imx9_ddr_perf.c
> b/drivers/perf/fsl_imx9_ddr_perf.c
> index fd118773508d..4bb80050920c 100644
> --- a/drivers/perf/fsl_imx9_ddr_perf.c
> +++ b/drivers/perf/fsl_imx9_ddr_perf.c
> @@ -51,6 +51,7 @@
> 
>  #define NUM_COUNTERS		11
>  #define CYCLES_COUNTER		0
> +#define CYCLES_EVENT_ID		0
> 
>  #define to_ddr_pmu(p)		container_of(p, struct ddr_pmu, pmu)
> 
> @@ -235,6 +236,14 @@ static struct attribute *ddr_perf_events_attrs[] = {
>  	NULL,
>  };
> 
> +static bool ddr_perf_is_specific_event(int event)

Why call specific? Name is too general.  Such as is_fixed? Or Is_with_filter? 
Need know what specific?

> +{
> +	if (event >= 64 && event <= 73)
> +		return true;
> +	else
> +		return false;
> +}
> +
>  static const struct attribute_group ddr_perf_events_attr_group = {
>  	.name = "events",
>  	.attrs = ddr_perf_events_attrs,
> @@ -507,6 +516,7 @@ static int ddr_perf_event_init(struct perf_event
> *event)
>  	struct ddr_pmu *pmu = to_ddr_pmu(event->pmu);
>  	struct hw_perf_event *hwc = &event->hw;
>  	struct perf_event *sibling;
> +	int event_id, counter;
> 
>  	if (event->attr.type != event->pmu->type)
>  		return -ENOENT;
> @@ -519,6 +529,18 @@ static int ddr_perf_event_init(struct perf_event
> *event)
>  		return -EOPNOTSUPP;
>  	}
> 
> +	counter = (event->attr.config & 0xFF00) >> 8;
 
Define 0xFF00?

> +	if (counter > NUM_COUNTERS) {
> +		dev_warn(pmu->dev, "Only counter 0-10 is supported!\n");
> +		return -EINVAL;
> +	}
> +
> +	event_id = event->attr.config & 0x00FF;

same for hardcode 0x00FF

> +	if (ddr_perf_is_specific_event(event_id) && counter == 0) {
> +		dev_err(pmu->dev, "Need specify counter for counter
> specific events!\n");
> +		return -EINVAL;
> +	}
> +
>  	/*
>  	 * We must NOT create groups containing mixed PMUs, although
> software
>  	 * events are acceptable (for example to create a CCN group
> @@ -552,6 +574,39 @@ static void ddr_perf_event_start(struct perf_event
> *event, int flags)
>  	hwc->state = 0;
>  }
> 
> +static int ddr_perf_alloc_counter(struct ddr_pmu *pmu, int event, int
> counter)
> +{
> +	int i;
> +
> +	if (event == CYCLES_EVENT_ID) {
> +		/*
> +		 * Always map cycle event to counter 0.
> +		 * Cycles counter is dedicated for cycle event
> +		 * can't used for the other events.
> +		 */
> +		if (pmu->events[CYCLES_COUNTER] == NULL)
> +			return CYCLES_COUNTER;
> +	} else if (counter != 0) {
> +		/*
> +		 * 1. ddr_perf_event_init() will make sure counter
> +		 *    is not 0 for counter specific events.
> +		 * 2. Allow specify counter for referene event too.
> +		 */
> +		if (pmu->events[counter] == NULL)
> +			return counter;
> +	} else {
> +		/*
> +		 * Counter may be 0 if user doesn't specify it.
> +		 * Auto allocate counter for referene event.
> +		 */
> +		for (i = 1; i < NUM_COUNTERS; i++)
> +			if (pmu->events[i] == NULL)
> +				return i;
> +	}
> +
> +	return -ENOENT;
> +}
> +
>  static int ddr_perf_event_add(struct perf_event *event, int flags)
>  {
>  	struct ddr_pmu *pmu = to_ddr_pmu(event->pmu);
> @@ -559,9 +614,17 @@ static int ddr_perf_event_add(struct perf_event
> *event, int flags)
>  	int cfg = event->attr.config;
>  	int cfg1 = event->attr.config1;
>  	int cfg2 = event->attr.config2;
> -	int counter;
> +	int event_id, counter;
> 
> -	counter = (cfg & 0x0000FF00) >> 8;
> +	event_id = cfg & 0x00FF;
> +	counter = (cfg & 0xFF00) >> 8;
> +
> +	/* check if counter is available */
> +	counter = ddr_perf_alloc_counter(pmu, event_id, counter);
> +	if (counter < 0) {
> +		dev_dbg(pmu->dev, "There are not enough counters\n");
> +		return -EOPNOTSUPP;
> +	}
> 
>  	pmu->events[counter] = event;
>  	pmu->active_events++;
> @@ -597,9 +660,11 @@ static void ddr_perf_event_del(struct perf_event
> *event, int flags)
>  {
>  	struct ddr_pmu *pmu = to_ddr_pmu(event->pmu);
>  	struct hw_perf_event *hwc = &event->hw;
> +	int counter = hwc->idx;
> 
>  	ddr_perf_event_stop(event, PERF_EF_UPDATE);
> 
> +	pmu->events[counter] = NULL;
>  	pmu->active_events--;
>  	hwc->idx = -1;
>  }
> --
> 2.34.1