[PATCH v4 0/6] perf: Add ioctl for PMU driver configuration

[PATCH v4 0/6] perf: Add ioctl for PMU driver configuration

[Mathieu Poirier]

This is the fourth iteration of a set that adds the capability to communicate
event specific configuration to PMU kernel drivers using an ioctl().  Though
targeted at the identification of CoreSight sinks when operating in CPU-wide
trace scenarios the functionality is made generic enough for anyone to use.

The work fits in a wider scheme to support CPU-wide trace scenarios on CoreSight
that is available here[1].  If someone is to test the functionality using this 
branch, note that only dumping of CPU-wide trace data is working.  Full decoding
capability is being verified.

Patch 1 to 3 deal with kernel enhancement to the perf core while patch 4 is
CoreSight specific.  Patches 5 and 6 concentrate on the perf tools.

# Before this set: 

root@juno:/home/linaro# perf record -e cs_etm/@20070000.etr/ -C 2,3 sleep 1
failed to mmap with 12 (Cannot allocate memory)

# After this set:

root@juno:/home/linaro# perf record -e cs_etm/@20070000.etr/ -C 2,3 sleep 1
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 4.145 MB perf.data ]


Thanks,
Mathieu

[1]. https://git.linaro.org/people/mathieu.poirier/coresight.git/log/?h=cpu-wide-coresight 

---
Changes for V4:
. Made passing of information between ioctl() and PMU simpler.
. Rebased to 4.20-rc4


Mathieu Poirier (6):
  perf: Introduce ioctl to communicate driver configuration to kernel
  perf/core: Use ioctl to communicate driver configuration to kernel
  perf/aux: Make perf_event accessible to setup_aux()
  coresight: Use PMU driver configuration for sink selection
  perf tools: Make perf_evsel accessible to PMU driver configuration
    code
  perf tools: Use ioctl function to send sink configuration to kernel

 arch/s390/kernel/perf_cpum_sf.c                  |  6 +--
 arch/x86/events/intel/bts.c                      |  4 +-
 arch/x86/events/intel/pt.c                       |  5 +-
 drivers/hwtracing/coresight/coresight-etm-perf.c | 64 ++++++++++++++++------
 drivers/perf/arm_spe_pmu.c                       |  6 +--
 include/linux/perf_event.h                       | 40 +++++++++++++-
 include/uapi/linux/perf_event.h                  |  1 +
 kernel/events/core.c                             | 69 ++++++++++++++++++++++++
 kernel/events/ring_buffer.c                      |  2 +-
 tools/include/uapi/linux/perf_event.h            |  1 +
 tools/perf/arch/arm/util/cs-etm.c                | 67 ++++++++++++++++++++++-
 tools/perf/arch/arm/util/cs-etm.h                |  3 +-
 tools/perf/util/drv_configs.c                    | 30 +++--------
 tools/perf/util/evsel.c                          |  7 +++
 tools/perf/util/evsel.h                          |  1 +
 tools/perf/util/pmu.h                            |  3 +-
 16 files changed, 257 insertions(+), 52 deletions(-)

-- 
2.7.4

[PATCH v4 1/6] perf: Introduce ioctl to communicate driver configuration to kernel

[Mathieu Poirier]

Adding a new IOCTL command to communicate PMU specific configuration to
PMU kernel drivers.  This can be anything a PMU might need for
configuration that doesn't fit in the perf_event_attr structure, such
as the CoreSight sink to use for a session.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 include/uapi/linux/perf_event.h       | 1 +
 tools/include/uapi/linux/perf_event.h | 1 +
 2 files changed, 2 insertions(+)

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 9de8780ac8d9..bb558caeb33b 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -462,6 +462,7 @@ struct perf_event_query_bpf {
 #define PERF_EVENT_IOC_PAUSE_OUTPUT		_IOW('$', 9, __u32)
 #define PERF_EVENT_IOC_QUERY_BPF		_IOWR('$', 10, struct perf_event_query_bpf *)
 #define PERF_EVENT_IOC_MODIFY_ATTRIBUTES	_IOW('$', 11, struct perf_event_attr *)
+#define PERF_EVENT_IOC_SET_DRV_CONFIG		_IOW('$', 12, char *)
 
 enum perf_event_ioc_flags {
 	PERF_IOC_FLAG_GROUP		= 1U << 0,
diff --git a/tools/include/uapi/linux/perf_event.h b/tools/include/uapi/linux/perf_event.h
index 9de8780ac8d9..bb558caeb33b 100644
--- a/tools/include/uapi/linux/perf_event.h
+++ b/tools/include/uapi/linux/perf_event.h
@@ -462,6 +462,7 @@ struct perf_event_query_bpf {
 #define PERF_EVENT_IOC_PAUSE_OUTPUT		_IOW('$', 9, __u32)
 #define PERF_EVENT_IOC_QUERY_BPF		_IOWR('$', 10, struct perf_event_query_bpf *)
 #define PERF_EVENT_IOC_MODIFY_ATTRIBUTES	_IOW('$', 11, struct perf_event_attr *)
+#define PERF_EVENT_IOC_SET_DRV_CONFIG		_IOW('$', 12, char *)
 
 enum perf_event_ioc_flags {
 	PERF_IOC_FLAG_GROUP		= 1U << 0,
-- 
2.7.4

Re: [PATCH v4 1/6] perf: Introduce ioctl to communicate driver configuration to kernel

[Greg KH]

On Wed, Nov 28, 2018 at 03:01:13PM -0700, Mathieu Poirier wrote:
> Adding a new IOCTL command to communicate PMU specific configuration to
> PMU kernel drivers.  This can be anything a PMU might need for
> configuration that doesn't fit in the perf_event_attr structure, such
> as the CoreSight sink to use for a session.
> 
> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> ---
>  include/uapi/linux/perf_event.h       | 1 +
>  tools/include/uapi/linux/perf_event.h | 1 +
>  2 files changed, 2 insertions(+)
> 
> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
> index 9de8780ac8d9..bb558caeb33b 100644
> --- a/include/uapi/linux/perf_event.h
> +++ b/include/uapi/linux/perf_event.h
> @@ -462,6 +462,7 @@ struct perf_event_query_bpf {
>  #define PERF_EVENT_IOC_PAUSE_OUTPUT		_IOW('$', 9, __u32)
>  #define PERF_EVENT_IOC_QUERY_BPF		_IOWR('$', 10, struct perf_event_query_bpf *)
>  #define PERF_EVENT_IOC_MODIFY_ATTRIBUTES	_IOW('$', 11, struct perf_event_attr *)
> +#define PERF_EVENT_IOC_SET_DRV_CONFIG		_IOW('$', 12, char *)


A generic "char *" that the kernel is then going to parse?  Can you make
any more flexible of a new syscall to the kernel that allows anyone to
do anything with this?  :)

Please make this a lot more specific, this is way to generic, sorry.

greg k-h

[PATCH v4 2/6] perf/core: Use ioctl to communicate driver configuration to kernel

[Mathieu Poirier]

This patch adds the mechanic needed for user space to send PMU specific
configuration to the kernel driver using an ioctl() command.  That way
events can keep track of options that don't fit in the perf_event_attr
structure like the selection of a CoreSight sink to use for the session.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 include/linux/perf_event.h | 38 +++++++++++++++++++++++++
 kernel/events/core.c       | 69 ++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 107 insertions(+)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 53c500f0ca79..629fa1e1d6cf 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -114,6 +114,14 @@ struct hw_perf_event_extra {
 	int		idx;	/* index in shared_regs->regs[] */
 };
 
+/*
+ * PMU driver configuration
+ */
+struct pmu_drv_config {
+	void		*config;
+	raw_spinlock_t	lock;
+};
+
 /**
  * struct hw_perf_event - performance event hardware details:
  */
@@ -178,6 +186,9 @@ struct hw_perf_event {
 	/* Last sync'ed generation of filters */
 	unsigned long			addr_filters_gen;
 
+	/* PMU driver configuration */
+	struct pmu_drv_config		drv_config;
+
 /*
  * hw_perf_event::state flags; used to track the PERF_EF_* state.
  */
@@ -447,6 +458,17 @@ struct pmu {
 	 * Filter events for PMU-specific reasons.
 	 */
 	int (*filter_match)		(struct perf_event *event); /* optional */
+
+	/*
+	 * Validate complex PMU configuration that don't fit in the
+	 * perf_event_attr struct.  Returns a PMU specific pointer or an error
+	 * value < 0.
+	 *
+	 * As with addr_filters_validate(), runs in the context of the ioctl()
+	 * process and is not serialized with the rest of the PMU callbacks.
+	 */
+	void *(*drv_config_validate)	(struct perf_event *event,
+					 char *config_str);
 };
 
 enum perf_addr_filter_action_t {
@@ -1235,6 +1257,11 @@ static inline bool has_addr_filter(struct perf_event *event)
 	return event->pmu->nr_addr_filters;
 }
 
+static inline bool has_drv_config(struct perf_event *event)
+{
+	return event->pmu->drv_config_validate;
+}
+
 /*
  * An inherited event uses parent's filters
  */
@@ -1249,6 +1276,17 @@ perf_event_addr_filters(struct perf_event *event)
 	return ifh;
 }
 
+static inline struct pmu_drv_config *
+perf_event_get_drv_config(struct perf_event *event)
+{
+	struct pmu_drv_config *cfg = &event->hw.drv_config;
+
+	if (event->parent)
+		cfg = &event->parent->hw.drv_config;
+
+	return cfg;
+}
+
 extern void perf_event_addr_filters_sync(struct perf_event *event);
 
 extern int perf_output_begin(struct perf_output_handle *handle,
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 84530ab358c3..a76c0ce39c4e 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5003,6 +5003,8 @@ static inline int perf_fget_light(int fd, struct fd *p)
 static int perf_event_set_output(struct perf_event *event,
 				 struct perf_event *output_event);
 static int perf_event_set_filter(struct perf_event *event, void __user *arg);
+static int perf_event_set_drv_config(struct perf_event *event,
+				     void __user *arg);
 static int perf_event_set_bpf_prog(struct perf_event *event, u32 prog_fd);
 static int perf_copy_attr(struct perf_event_attr __user *uattr,
 			  struct perf_event_attr *attr);
@@ -5089,6 +5091,10 @@ static long _perf_ioctl(struct perf_event *event, unsigned int cmd, unsigned lon
 
 		return perf_event_modify_attr(event,  &new_attr);
 	}
+
+	case PERF_EVENT_IOC_SET_DRV_CONFIG:
+		return perf_event_set_drv_config(event, (void __user *)arg);
+
 	default:
 		return -ENOTTY;
 	}
@@ -9128,6 +9134,68 @@ static int perf_event_set_filter(struct perf_event *event, void __user *arg)
 	return ret;
 }
 
+static void perf_drv_config_replace(struct perf_event *event, void *drv_data)
+{
+	unsigned long flags;
+	struct pmu_drv_config *drv_config = &event->hw.drv_config;
+
+	if (!has_drv_config(event))
+		return;
+
+	/* Children take their configuration from their parent */
+	if (event->parent)
+		return;
+
+	/* Make sure the PMU doesn't get a handle on the data */
+	raw_spin_lock_irqsave(&drv_config->lock, flags);
+	drv_config->config = drv_data;
+	raw_spin_unlock_irqrestore(&drv_config->lock, flags);
+}
+
+static int
+perf_event_process_drv_config(struct perf_event *event, char *config_str)
+{
+	int ret = -EINVAL;
+	void *drv_data;
+
+	/* Make sure ctx.mutex is held */
+	lockdep_assert_held(&event->ctx->mutex);
+
+	/* Children take their configuration from their parent */
+	if (WARN_ON_ONCE(event->parent))
+		goto out;
+
+	drv_data = event->pmu->drv_config_validate(event, config_str);
+	if (IS_ERR(drv_data)) {
+		ret = PTR_ERR(drv_data);
+		goto out;
+	}
+
+	perf_drv_config_replace(event, drv_data);
+
+	ret = 0;
+out:
+	return ret;
+}
+
+static int perf_event_set_drv_config(struct perf_event *event, void __user *arg)
+{
+	int ret = -EINVAL;
+	char *config_str;
+
+	if (!has_drv_config(event))
+		return ret;
+
+	config_str = strndup_user(arg, PAGE_SIZE);
+	if (IS_ERR(config_str))
+		return PTR_ERR(config_str);
+
+	ret = perf_event_process_drv_config(event, config_str);
+
+	kfree(config_str);
+	return ret;
+}
+
 /*
  * hrtimer based swevent callback
  */
@@ -10052,6 +10120,7 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
 	if (attr->freq && attr->sample_freq)
 		hwc->sample_period = 1;
 	hwc->last_period = hwc->sample_period;
+	raw_spin_lock_init(&hwc->drv_config.lock);
 
 	local64_set(&hwc->period_left, hwc->sample_period);
 
-- 
2.7.4

Re: [PATCH v4 2/6] perf/core: Use ioctl to communicate driver configuration to kernel

[Greg KH]

On Wed, Nov 28, 2018 at 03:01:14PM -0700, Mathieu Poirier wrote:
> This patch adds the mechanic needed for user space to send PMU specific
> configuration to the kernel driver using an ioctl() command.  That way
> events can keep track of options that don't fit in the perf_event_attr
> structure like the selection of a CoreSight sink to use for the session.

This is what configfs is for, please use that instead of a generic "send
a string to the kernel for it to parse" type of thing.  No other driver
does this (or if they do, they should not), so this driver should not do
it as well, sorry.

greg k-h

[PATCH v4 3/6] perf/aux: Make perf_event accessible to setup_aux()

[Mathieu Poirier]

When pmu::setup_aux() is called the coresight PMU needs to know which
sink to use for the session by looking up the information in the
drv_config field of the hw_perf_event structure.

As such simply replace the cpu information by the complete perf_event
structure and change all affected customers.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 arch/s390/kernel/perf_cpum_sf.c                  | 6 +++---
 arch/x86/events/intel/bts.c                      | 4 +++-
 arch/x86/events/intel/pt.c                       | 5 +++--
 drivers/hwtracing/coresight/coresight-etm-perf.c | 6 +++---
 drivers/perf/arm_spe_pmu.c                       | 6 +++---
 include/linux/perf_event.h                       | 2 +-
 kernel/events/ring_buffer.c                      | 2 +-
 7 files changed, 17 insertions(+), 14 deletions(-)

diff --git a/arch/s390/kernel/perf_cpum_sf.c b/arch/s390/kernel/perf_cpum_sf.c
index 7bf604ff50a1..df92c2af99b6 100644
--- a/arch/s390/kernel/perf_cpum_sf.c
+++ b/arch/s390/kernel/perf_cpum_sf.c
@@ -1600,7 +1600,7 @@ static void aux_sdb_init(unsigned long sdb)
 
 /*
  * aux_buffer_setup() - Setup AUX buffer for diagnostic mode sampling
- * @cpu:	On which to allocate, -1 means current
+ * @event:	Event the buffer is setup for, event->cpu == -1 means current
  * @pages:	Array of pointers to buffer pages passed from perf core
  * @nr_pages:	Total pages
  * @snapshot:	Flag for snapshot mode
@@ -1612,8 +1612,8 @@ static void aux_sdb_init(unsigned long sdb)
  *
  * Return the private AUX buffer structure if success or NULL if fails.
  */
-static void *aux_buffer_setup(int cpu, void **pages, int nr_pages,
-			      bool snapshot)
+static void *aux_buffer_setup(struct perf_event *event, void **pages,
+			      int nr_pages, bool snapshot)
 {
 	struct sf_buffer *sfb;
 	struct aux_buffer *aux;
diff --git a/arch/x86/events/intel/bts.c b/arch/x86/events/intel/bts.c
index 24ffa1e88cf9..7139f6bf27ad 100644
--- a/arch/x86/events/intel/bts.c
+++ b/arch/x86/events/intel/bts.c
@@ -77,10 +77,12 @@ static size_t buf_size(struct page *page)
 }
 
 static void *
-bts_buffer_setup_aux(int cpu, void **pages, int nr_pages, bool overwrite)
+bts_buffer_setup_aux(struct perf_event *event, void **pages,
+		     int nr_pages, bool overwrite)
 {
 	struct bts_buffer *buf;
 	struct page *page;
+	int cpu = event->cpu;
 	int node = (cpu == -1) ? cpu : cpu_to_node(cpu);
 	unsigned long offset;
 	size_t size = nr_pages << PAGE_SHIFT;
diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index 3a0aa83cbd07..f7ec5c5fbf0a 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -1104,10 +1104,11 @@ static int pt_buffer_init_topa(struct pt_buffer *buf, unsigned long nr_pages,
  * Return:	Our private PT buffer structure.
  */
 static void *
-pt_buffer_setup_aux(int cpu, void **pages, int nr_pages, bool snapshot)
+pt_buffer_setup_aux(struct perf_event *event, void **pages,
+		    int nr_pages, bool snapshot)
 {
 	struct pt_buffer *buf;
-	int node, ret;
+	int node, ret, cpu = event->cpu;
 
 	if (!nr_pages)
 		return NULL;
diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index abe8249b893b..f21eb28b6782 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -177,15 +177,15 @@ static void etm_free_aux(void *data)
 	schedule_work(&event_data->work);
 }
 
-static void *etm_setup_aux(int event_cpu, void **pages,
+static void *etm_setup_aux(struct perf_event *event, void **pages,
 			   int nr_pages, bool overwrite)
 {
-	int cpu;
+	int cpu = event->cpu;
 	cpumask_t *mask;
 	struct coresight_device *sink;
 	struct etm_event_data *event_data = NULL;
 
-	event_data = alloc_event_data(event_cpu);
+	event_data = alloc_event_data(cpu);
 	if (!event_data)
 		return NULL;
 	INIT_WORK(&event_data->work, free_event_data);
diff --git a/drivers/perf/arm_spe_pmu.c b/drivers/perf/arm_spe_pmu.c
index 54ec278d2fc4..4dcd7bf14dcc 100644
--- a/drivers/perf/arm_spe_pmu.c
+++ b/drivers/perf/arm_spe_pmu.c
@@ -824,10 +824,10 @@ static void arm_spe_pmu_read(struct perf_event *event)
 {
 }
 
-static void *arm_spe_pmu_setup_aux(int cpu, void **pages, int nr_pages,
-				   bool snapshot)
+static void *arm_spe_pmu_setup_aux(struct perf_event *event, void **pages,
+				   int nr_pages, bool snapshot)
 {
-	int i;
+	int i, cpu = event->cpu;
 	struct page **pglist;
 	struct arm_spe_pmu_buf *buf;
 
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 629fa1e1d6cf..c17cbba10b30 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -420,7 +420,7 @@ struct pmu {
 	/*
 	 * Set up pmu-private data structures for an AUX area
 	 */
-	void *(*setup_aux)		(int cpu, void **pages,
+	void *(*setup_aux)		(struct perf_event *event, void **pages,
 					 int nr_pages, bool overwrite);
 					/* optional */
 
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 4a9937076331..857308295f63 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -658,7 +658,7 @@ int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event,
 			goto out;
 	}
 
-	rb->aux_priv = event->pmu->setup_aux(event->cpu, rb->aux_pages, nr_pages,
+	rb->aux_priv = event->pmu->setup_aux(event, rb->aux_pages, nr_pages,
 					     overwrite);
 	if (!rb->aux_priv)
 		goto out;
-- 
2.7.4

[PATCH v4 4/6] coresight: Use PMU driver configuration for sink selection

[Mathieu Poirier]

This patch uses the PMU driver configuration held in event::hw::drv_config
to select a sink for each event that is created (the old sysFS way of
working is kept around for backward compatibility).

By proceeding in this way a sink can be used by multiple sessions
without having to play games with entries in sysFS.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 drivers/hwtracing/coresight/coresight-etm-perf.c | 58 +++++++++++++++++++-----
 1 file changed, 46 insertions(+), 12 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index f21eb28b6782..0fbff912d515 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -14,6 +14,7 @@
 #include <linux/perf_event.h>
 #include <linux/percpu-defs.h>
 #include <linux/slab.h>
+#include <linux/string.h>
 #include <linux/types.h>
 #include <linux/workqueue.h>
 
@@ -177,6 +178,26 @@ static void etm_free_aux(void *data)
 	schedule_work(&event_data->work);
 }
 
+static struct coresight_device *etm_drv_config_sync(struct perf_event *event)
+{
+	struct coresight_device *sink = NULL;
+	struct pmu_drv_config *drv_config = perf_event_get_drv_config(event);
+
+	/*
+	 * Make sure we don't race with perf_drv_config_replace() in
+	 * kernel/events/core.c.
+	 */
+	raw_spin_lock(&drv_config->lock);
+
+	/* Copy what we got from user space if applicable. */
+	if (drv_config->config)
+		sink = drv_config->config;
+
+	raw_spin_unlock(&drv_config->lock);
+
+	return sink;
+}
+
 static void *etm_setup_aux(struct perf_event *event, void **pages,
 			   int nr_pages, bool overwrite)
 {
@@ -190,18 +211,11 @@ static void *etm_setup_aux(struct perf_event *event, void **pages,
 		return NULL;
 	INIT_WORK(&event_data->work, free_event_data);
 
-	/*
-	 * In theory nothing prevent tracers in a trace session from being
-	 * associated with different sinks, nor having a sink per tracer.  But
-	 * until we have HW with this kind of topology we need to assume tracers
-	 * in a trace session are using the same sink.  Therefore go through
-	 * the coresight bus and pick the first enabled sink.
-	 *
-	 * When operated from sysFS users are responsible to enable the sink
-	 * while from perf, the perf tools will do it based on the choice made
-	 * on the cmd line.  As such the "enable_sink" flag in sysFS is reset.
-	 */
-	sink = coresight_get_enabled_sink(true);
+	/* First get the sink config from user space. */
+	sink = etm_drv_config_sync(event);
+	if (!sink)
+		sink = coresight_get_enabled_sink(true);
+
 	if (!sink || !sink_ops(sink)->alloc_buffer)
 		goto err;
 
@@ -454,6 +468,25 @@ static void etm_addr_filters_sync(struct perf_event *event)
 	filters->nr_filters = i;
 }
 
+static void *etm_drv_config_validate(struct perf_event *event, char *cstr)
+{
+	char drv_config[NAME_MAX];
+	struct device *dev;
+	struct coresight_device *sink;
+
+	strncpy(drv_config, cstr, NAME_MAX);
+
+	/* Look for the device with that name on the CS bus. */
+	dev = bus_find_device_by_name(&coresight_bustype, NULL, drv_config);
+	if (!dev)
+		return ERR_PTR(-EINVAL);
+
+	sink = to_coresight_device(dev);
+	put_device(dev);
+
+	return sink;
+}
+
 int etm_perf_symlink(struct coresight_device *csdev, bool link)
 {
 	char entry[sizeof("cpu9999999")];
@@ -498,6 +531,7 @@ static int __init etm_perf_init(void)
 	etm_pmu.addr_filters_sync	= etm_addr_filters_sync;
 	etm_pmu.addr_filters_validate	= etm_addr_filters_validate;
 	etm_pmu.nr_addr_filters		= ETM_ADDR_CMP_MAX;
+	etm_pmu.drv_config_validate	= etm_drv_config_validate;
 
 	ret = perf_pmu_register(&etm_pmu, CORESIGHT_ETM_PMU_NAME, -1);
 	if (ret == 0)
-- 
2.7.4

Re: [PATCH v4 4/6] coresight: Use PMU driver configuration for sink selection

[Greg KH]

On Wed, Nov 28, 2018 at 03:01:16PM -0700, Mathieu Poirier wrote:
> This patch uses the PMU driver configuration held in event::hw::drv_config
> to select a sink for each event that is created (the old sysFS way of
> working is kept around for backward compatibility).

It is "sysfs", no InterCaps please, I've never called it that in the
past.

And just use sysfs, if that does not work properly, then fix that, don't
create yet-another-way-to-configure-this-thing to just confuse people.

thanks,

greg k-h

Re: [PATCH v4 4/6] coresight: Use PMU driver configuration for sink selection

[Mathieu Poirier]

Hi Greg,

On Thu, Nov 29, 2018 at 08:49:36AM +0100, Greg KH wrote:
> On Wed, Nov 28, 2018 at 03:01:16PM -0700, Mathieu Poirier wrote:
> > This patch uses the PMU driver configuration held in event::hw::drv_config
> > to select a sink for each event that is created (the old sysFS way of
> > working is kept around for backward compatibility).
> 
> It is "sysfs", no InterCaps please, I've never called it that in the
> past.
> 
> And just use sysfs, if that does not work properly, then fix that, don't
> create yet-another-way-to-configure-this-thing to just confuse people.

Thanks for the review, you've provided usefull comments.

Regarding the "char *" argument for the ioctl, I followed an example that
currently exist but I can proceed differently.  

My goal with this patchset was specifically to fix what is wrong with sysfs and
completely take it out of the equation.  The only reason to keep the kernel 
interface alive was to prevent braking older user space perf tools currently
using it.  

I chose to use an ioctl() because it is flexible and well suited for the dynamic
nature of perf events.  It is also currently used to set various event specific 
configuration so doing the same adds to the established pattern and avoids
creating a new way of doing things, something the perf crew would have been
quick to point out.

Was my approach wrong?

Regards,
Mathieu

> 
> thanks,
> 
> greg k-h

Re: [PATCH v4 4/6] coresight: Use PMU driver configuration for sink selection

[Greg KH]

On Thu, Nov 29, 2018 at 04:09:15PM -0700, Mathieu Poirier wrote:
> Hi Greg,
> 
> On Thu, Nov 29, 2018 at 08:49:36AM +0100, Greg KH wrote:
> > On Wed, Nov 28, 2018 at 03:01:16PM -0700, Mathieu Poirier wrote:
> > > This patch uses the PMU driver configuration held in event::hw::drv_config
> > > to select a sink for each event that is created (the old sysFS way of
> > > working is kept around for backward compatibility).
> > 
> > It is "sysfs", no InterCaps please, I've never called it that in the
> > past.
> > 
> > And just use sysfs, if that does not work properly, then fix that, don't
> > create yet-another-way-to-configure-this-thing to just confuse people.
> 
> Thanks for the review, you've provided usefull comments.
> 
> Regarding the "char *" argument for the ioctl, I followed an example that
> currently exist but I can proceed differently.  

What driver currently uses a char * on an ioctl to parse arbritrary
userspace information to set its configuration?  That should be fixed...

> My goal with this patchset was specifically to fix what is wrong with sysfs and
> completely take it out of the equation.  The only reason to keep the kernel 
> interface alive was to prevent braking older user space perf tools currently
> using it.  

That's fine, just don't create a new syscall that takes arbritrary data
and parses it in the kernel, that's not ok.

> I chose to use an ioctl() because it is flexible and well suited for the dynamic
> nature of perf events.  It is also currently used to set various event specific 
> configuration so doing the same adds to the established pattern and avoids
> creating a new way of doing things, something the perf crew would have been
> quick to point out.
> 
> Was my approach wrong?

I don't know how the perf interface works, so perhaps work with those
developers to sync up and match what they use today?

But step back, what exactly are you trying to do here?  You have an
implementation of a solution but I don't see the problem stated anywhere
here.

thanks,

greg k-h

Re: [PATCH v4 4/6] coresight: Use PMU driver configuration for sink selection

[Mathieu Poirier]

On Fri, 30 Nov 2018 at 00:42, Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Thu, Nov 29, 2018 at 04:09:15PM -0700, Mathieu Poirier wrote:
> > Hi Greg,
> >
> > On Thu, Nov 29, 2018 at 08:49:36AM +0100, Greg KH wrote:
> > > On Wed, Nov 28, 2018 at 03:01:16PM -0700, Mathieu Poirier wrote:
> > > > This patch uses the PMU driver configuration held in event::hw::drv_config
> > > > to select a sink for each event that is created (the old sysFS way of
> > > > working is kept around for backward compatibility).
> > >
> > > It is "sysfs", no InterCaps please, I've never called it that in the
> > > past.
> > >
> > > And just use sysfs, if that does not work properly, then fix that, don't
> > > create yet-another-way-to-configure-this-thing to just confuse people.
> >
> > Thanks for the review, you've provided usefull comments.
> >
> > Regarding the "char *" argument for the ioctl, I followed an example that
> > currently exist but I can proceed differently.
>
> What driver currently uses a char * on an ioctl to parse arbritrary
> userspace information to set its configuration?  That should be fixed...
>

Perf filters [1] are communicated to the kernel as a char *.  Given
the dynamic nature of event creation I really don't know how else it
could have been done.

[1]. https://elixir.bootlin.com/linux/latest/source/include/uapi/linux/perf_event.h#L459

> > My goal with this patchset was specifically to fix what is wrong with sysfs and
> > completely take it out of the equation.  The only reason to keep the kernel
> > interface alive was to prevent braking older user space perf tools currently
> > using it.
>
> That's fine, just don't create a new syscall that takes arbritrary data
> and parses it in the kernel, that's not ok.

You got it.

>
> > I chose to use an ioctl() because it is flexible and well suited for the dynamic
> > nature of perf events.  It is also currently used to set various event specific
> > configuration so doing the same adds to the established pattern and avoids
> > creating a new way of doing things, something the perf crew would have been
> > quick to point out.
> >
> > Was my approach wrong?
>
> I don't know how the perf interface works, so perhaps work with those
> developers to sync up and match what they use today?

I have already done a fair amount of work with them.

>
> But step back, what exactly are you trying to do here?  You have an
> implementation of a solution but I don't see the problem stated anywhere
> here.

In the coresight world there can be more than one sink to aggregate
trace data generated by CPUs, hence the need for users to select which
one to use from the perf command line.

Up until now sysfs was used to communicate sink information to the
kernel but that was never the right way to proceed because it breaks
when more than one perf session are created at the same time.  The
situation was manageable when working with per-thread scenarios where
a single HW trace event is created but in CPU-wide mode a HW trace
event is created for each CPU that is specified on the perf command
line, taking us back to the concurrency problem we have when dealing
with multiple per-thread session.

Since my goal is to add coresight support for CPU-wide trace
scenarios, the issue with sysfs concurrency needs to be addressed
first, which this set is aiming at.  Sysfs is a problem so I'm
removing it in favour of an ioctl() where a specific sink can be
assigned to each event.

The above should probably go in the cover letter.  Let me know if you
want more information.

Thanks,
Mathieu

[PATCH v4 5/6] perf tools: Make perf_evsel accessible to PMU driver configuration code

[Mathieu Poirier]

Make the perf_evsel available to the PMU driver configuration code.  That
way function perf_evsel__run_ioctl() can be used from there and
information pertaining to the perf_evsel_config_term is still available.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 tools/perf/arch/arm/util/cs-etm.c | 22 +++++++++++++++++++++-
 tools/perf/arch/arm/util/cs-etm.h |  3 ++-
 tools/perf/util/drv_configs.c     | 30 +++++++-----------------------
 tools/perf/util/pmu.h             |  3 ++-
 4 files changed, 32 insertions(+), 26 deletions(-)

diff --git a/tools/perf/arch/arm/util/cs-etm.c b/tools/perf/arch/arm/util/cs-etm.c
index 2f595cd73da6..d8081c2e6d44 100644
--- a/tools/perf/arch/arm/util/cs-etm.c
+++ b/tools/perf/arch/arm/util/cs-etm.c
@@ -635,7 +635,7 @@ static int __printf(2, 3) cs_device__print_file(const char *name, const char *fm
 	return ret;
 }
 
-int cs_etm_set_drv_config(struct perf_evsel_config_term *term)
+static int cs_etm_set_drv_config_term(struct perf_evsel_config_term *term)
 {
 	int ret;
 	char enable_sink[ENABLE_SINK_MAX];
@@ -649,3 +649,23 @@ int cs_etm_set_drv_config(struct perf_evsel_config_term *term)
 
 	return 0;
 }
+
+int cs_etm_set_drv_config(struct perf_evsel *evsel,
+			  struct perf_evsel_config_term **err_term)
+{
+	int err = 0;
+	struct perf_evsel_config_term *term;
+
+	list_for_each_entry(term, &evsel->config_terms, list) {
+		if (term->type != PERF_EVSEL__CONFIG_TERM_DRV_CFG)
+			continue;
+
+		err = cs_etm_set_drv_config_term(term);
+		if (err) {
+			*err_term = term;
+			break;
+		}
+	}
+
+	return err;
+}
diff --git a/tools/perf/arch/arm/util/cs-etm.h b/tools/perf/arch/arm/util/cs-etm.h
index 1a12e64f5127..a3f8dde6ccef 100644
--- a/tools/perf/arch/arm/util/cs-etm.h
+++ b/tools/perf/arch/arm/util/cs-etm.h
@@ -10,6 +10,7 @@
 #include "../../util/evsel.h"
 
 struct auxtrace_record *cs_etm_record_init(int *err);
-int cs_etm_set_drv_config(struct perf_evsel_config_term *term);
+int cs_etm_set_drv_config(struct perf_evsel *evsel,
+			  struct perf_evsel_config_term **err_term);
 
 #endif
diff --git a/tools/perf/util/drv_configs.c b/tools/perf/util/drv_configs.c
index eec754243f4d..f7c1bcf08549 100644
--- a/tools/perf/util/drv_configs.c
+++ b/tools/perf/util/drv_configs.c
@@ -25,7 +25,6 @@ perf_evsel__apply_drv_configs(struct perf_evsel *evsel,
 {
 	bool found = false;
 	int err = 0;
-	struct perf_evsel_config_term *term;
 	struct perf_pmu *pmu = NULL;
 
 	while ((pmu = perf_pmu__scan(pmu)) != NULL)
@@ -34,29 +33,14 @@ perf_evsel__apply_drv_configs(struct perf_evsel *evsel,
 			break;
 		}
 
-	list_for_each_entry(term, &evsel->config_terms, list) {
-		if (term->type != PERF_EVSEL__CONFIG_TERM_DRV_CFG)
-			continue;
+	/*
+	 * No need to continue if we didn't get a match or if there is no
+	 * driver configuration function for this PMU.
+	 */
+	if (!found || !pmu->set_drv_config)
+		return err;
 
-		/*
-		 * We have a configuration term, report an error if we
-		 * can't find the PMU or if the PMU driver doesn't support
-		 * cmd line driver configuration.
-		 */
-		if (!found || !pmu->set_drv_config) {
-			err = -EINVAL;
-			*err_term = term;
-			break;
-		}
-
-		err = pmu->set_drv_config(term);
-		if (err) {
-			*err_term = term;
-			break;
-		}
-	}
-
-	return err;
+	return pmu->set_drv_config(evsel, err_term);
 }
 
 int perf_evlist__apply_drv_configs(struct perf_evlist *evlist,
diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
index 76fecec7b3f9..47f44394042b 100644
--- a/tools/perf/util/pmu.h
+++ b/tools/perf/util/pmu.h
@@ -29,7 +29,8 @@ struct perf_pmu {
 	struct list_head format;  /* HEAD struct perf_pmu_format -> list */
 	struct list_head aliases; /* HEAD struct perf_pmu_alias -> list */
 	struct list_head list;    /* ELEM */
-	int (*set_drv_config)	(struct perf_evsel_config_term *term);
+	int (*set_drv_config)	(struct perf_evsel *evsel,
+				 struct perf_evsel_config_term **err_term);
 };
 
 struct perf_pmu_info {
-- 
2.7.4

[PATCH v4 6/6] perf tools: Use ioctl function to send sink configuration to kernel

[Mathieu Poirier]

The communication of sink information for a trace session doesn't work when
more than one CPU is involved in the scenario due to the static nature of
sysFS.  As such communicate the sink information to each event by using the
driver's sink configuration information and an ioctl command.

Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
---
 tools/perf/arch/arm/util/cs-etm.c | 49 +++++++++++++++++++++++++++++++++++++--
 tools/perf/util/evsel.c           |  7 ++++++
 tools/perf/util/evsel.h           |  1 +
 3 files changed, 55 insertions(+), 2 deletions(-)

diff --git a/tools/perf/arch/arm/util/cs-etm.c b/tools/perf/arch/arm/util/cs-etm.c
index d8081c2e6d44..4f0563b99a07 100644
--- a/tools/perf/arch/arm/util/cs-etm.c
+++ b/tools/perf/arch/arm/util/cs-etm.c
@@ -619,6 +619,26 @@ static FILE *cs_device__open_file(const char *name)
 
 }
 
+static int cs_etm_check_drv_config_term(const char *name)
+{
+	struct stat st;
+	char path[PATH_MAX];
+	const char *sysfs;
+
+	/* CS devices are all found under sysFS */
+	sysfs = sysfs__mountpoint();
+	if (!sysfs)
+		return -EINVAL;
+
+	snprintf(path, PATH_MAX,
+		 "%s" CS_BUS_DEVICE_PATH "%s", sysfs, name);
+
+	if (stat(path, &st) < 0)
+		return -EINVAL;
+
+	return 0;
+}
+
 static int __printf(2, 3) cs_device__print_file(const char *name, const char *fmt, ...)
 {
 	va_list args;
@@ -635,7 +655,7 @@ static int __printf(2, 3) cs_device__print_file(const char *name, const char *fm
 	return ret;
 }
 
-static int cs_etm_set_drv_config_term(struct perf_evsel_config_term *term)
+static int cs_etm_set_drv_config_term_sysfs(struct perf_evsel_config_term *term)
 {
 	int ret;
 	char enable_sink[ENABLE_SINK_MAX];
@@ -650,6 +670,21 @@ static int cs_etm_set_drv_config_term(struct perf_evsel_config_term *term)
 	return 0;
 }
 
+static int cs_etm_set_drv_config_term_ioctl(struct perf_evsel *evsel,
+					    struct perf_evsel_config_term *term)
+{
+	int ret;
+	const char *drv_cfg = term->val.drv_cfg;
+
+	/* First check the input */
+	ret = cs_etm_check_drv_config_term(drv_cfg);
+	if (ret)
+		return ret;
+
+	/* All good, apply configuration */
+	return perf_evsel__apply_drv_config(evsel, drv_cfg);
+}
+
 int cs_etm_set_drv_config(struct perf_evsel *evsel,
 			  struct perf_evsel_config_term **err_term)
 {
@@ -660,7 +695,17 @@ int cs_etm_set_drv_config(struct perf_evsel *evsel,
 		if (term->type != PERF_EVSEL__CONFIG_TERM_DRV_CFG)
 			continue;
 
-		err = cs_etm_set_drv_config_term(term);
+		/* First try the new interface, i.e ioctl() */
+		err = cs_etm_set_drv_config_term_ioctl(evsel, term);
+		if (!err)
+			continue;
+
+		/*
+		 * Something went wrong, we are probably working with an older
+		 * kernel.  As such use the sysFS interface, which will only
+		 * work for per-thread scenarios.
+		 */
+		err = cs_etm_set_drv_config_term_sysfs(term);
 		if (err) {
 			*err_term = term;
 			break;
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 6d187059a373..a0374dab843f 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1195,6 +1195,13 @@ static int perf_evsel__append_filter(struct perf_evsel *evsel,
 	return -1;
 }
 
+int perf_evsel__apply_drv_config(struct perf_evsel *evsel, const char *config)
+{
+	return perf_evsel__run_ioctl(evsel,
+				     PERF_EVENT_IOC_SET_DRV_CONFIG,
+				     (void *)config);
+}
+
 int perf_evsel__append_tp_filter(struct perf_evsel *evsel, const char *filter)
 {
 	return perf_evsel__append_filter(evsel, "(%s) && (%s)", filter);
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index 3147ca76c6fc..30083b0ae62c 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -276,6 +276,7 @@ int perf_evsel__append_tp_filter(struct perf_evsel *evsel, const char *filter);
 int perf_evsel__append_addr_filter(struct perf_evsel *evsel,
 				   const char *filter);
 int perf_evsel__apply_filter(struct perf_evsel *evsel, const char *filter);
+int perf_evsel__apply_drv_config(struct perf_evsel *evsel, const char *config);
 int perf_evsel__enable(struct perf_evsel *evsel);
 int perf_evsel__disable(struct perf_evsel *evsel);
 
-- 
2.7.4