[PATCH v3 08/46] perf/x86/intel/cmt: add MONitored Resource (monr) initialization

[David Carrillo-Cisneros <davidcc@google.com>]

Events use monrs to monitor CMT events. Events that share their
monitoring target (same thread or cgroup) share a monr.

This patch introduces monrs and adds support for monr creation/destruction.

An event's associated monr is referenced by event->cmt_monr (introduced
in previous patch).

monr->mon_events references the first event that uses that monr and events
that share monr are appended to first event's cmt_list list head.

Hold all pkgd->mutex to modify monr->mon_events and event's data.

Support for CPU and cgroups is added in future patches in this series.

More details in code's comments.

Signed-off-by: David Carrillo-Cisneros <davidcc@google.com>
---
 arch/x86/events/intel/cmt.c | 228 ++++++++++++++++++++++++++++++++++++++++++++
 arch/x86/events/intel/cmt.h |  20 ++++
 2 files changed, 248 insertions(+)

diff --git a/arch/x86/events/intel/cmt.c b/arch/x86/events/intel/cmt.c
index 0a24896..23606a7 100644
--- a/arch/x86/events/intel/cmt.c
+++ b/arch/x86/events/intel/cmt.c
@@ -19,6 +19,8 @@ static struct lock_class_key	lock_keys[CMT_MAX_NR_PKGS];
 #endif
 
 static DEFINE_MUTEX(cmt_mutex);
+/* List of monrs that are associated with an event. */
+static LIST_HEAD(cmt_event_monrs);
 
 static unsigned int cmt_l3_scale;	/* cmt hw units to bytes. */
 
@@ -49,8 +51,210 @@ static struct pkg_data *cmt_pkgs_data_next_rcu(struct pkg_data *pkgd)
 	return pkgd;
 }
 
+/*
+ * Functions to lock/unlock/assert all per-package mutexes/locks at once.
+ */
+
+static void monr_hrchy_acquire_mutexes(void)
+{
+	struct pkg_data *pkgd = NULL;
+
+	/* RCU protected by cmt_mutex. */
+	while ((pkgd = cmt_pkgs_data_next_rcu(pkgd)))
+		mutex_lock(&pkgd->mutex);
+}
+
+static void monr_hrchy_release_mutexes(void)
+{
+	struct pkg_data *pkgd = NULL;
+
+	/* RCU protected by cmt_mutex. */
+	while ((pkgd = cmt_pkgs_data_next_rcu(pkgd)))
+		mutex_unlock(&pkgd->mutex);
+}
+
+static void monr_hrchy_assert_held_mutexes(void)
+{
+	struct pkg_data *pkgd = NULL;
+
+	/* RCU protected by cmt_mutex. */
+	while ((pkgd = cmt_pkgs_data_next_rcu(pkgd)))
+		lockdep_assert_held(&pkgd->mutex);
+}
+
+static void monr_dealloc(struct monr *monr)
+{
+	kfree(monr);
+}
+
+static struct monr *monr_alloc(void)
+{
+	struct monr *monr;
+
+	lockdep_assert_held(&cmt_mutex);
+
+	monr = kzalloc(sizeof(*monr), GFP_KERNEL);
+	if (!monr)
+		return ERR_PTR(-ENOMEM);
+
+	return monr;
+}
+
+static inline struct monr *monr_from_event(struct perf_event *event)
+{
+	return (struct monr *) READ_ONCE(event->hw.cmt_monr);
+}
+
+static struct monr *monr_remove_event(struct perf_event *event)
+{
+	struct monr *monr = monr_from_event(event);
+
+	lockdep_assert_held(&cmt_mutex);
+	monr_hrchy_assert_held_mutexes();
+
+	if (list_empty(&monr->mon_events->hw.cmt_list)) {
+		monr->mon_events = NULL;
+		/* remove from cmt_event_monrs */
+		list_del_init(&monr->entry);
+	} else {
+		if (monr->mon_events == event)
+			monr->mon_events = list_next_entry(event, hw.cmt_list);
+		list_del_init(&event->hw.cmt_list);
+	}
+
+	WRITE_ONCE(event->hw.cmt_monr, NULL);
+
+	return monr;
+}
+
+static int monr_append_event(struct monr *monr, struct perf_event *event)
+{
+	lockdep_assert_held(&cmt_mutex);
+	monr_hrchy_assert_held_mutexes();
+
+	if (monr->mon_events) {
+		list_add_tail(&event->hw.cmt_list,
+			      &monr->mon_events->hw.cmt_list);
+	} else {
+		monr->mon_events = event;
+		list_add_tail(&monr->entry, &cmt_event_monrs);
+	}
+
+	WRITE_ONCE(event->hw.cmt_monr, monr);
+
+	return 0;
+}
+
+static bool is_cgroup_event(struct perf_event *event)
+{
+	return false;
+}
+
+static int monr_hrchy_attach_cgroup_event(struct perf_event *event)
+{
+	return -EPERM;
+}
+
+static int monr_hrchy_attach_cpu_event(struct perf_event *event)
+{
+	return -EPERM;
+}
+
+static int monr_hrchy_attach_task_event(struct perf_event *event)
+{
+	struct monr *monr;
+	int err;
+
+	monr = monr_alloc();
+	if (IS_ERR(monr))
+		return -ENOMEM;
+
+	err = monr_append_event(monr, event);
+	if (err)
+		monr_dealloc(monr);
+	return err;
+}
+
+/* Insert or create monr in appropriate position in hierarchy. */
+static int monr_hrchy_attach_event(struct perf_event *event)
+{
+	int err = 0;
+
+	lockdep_assert_held(&cmt_mutex);
+	monr_hrchy_acquire_mutexes();
+
+	if (!is_cgroup_event(event) &&
+	    !(event->attach_state & PERF_ATTACH_TASK)) {
+		err = monr_hrchy_attach_cpu_event(event);
+		goto exit;
+	}
+	if (is_cgroup_event(event)) {
+		err = monr_hrchy_attach_cgroup_event(event);
+		goto exit;
+	}
+	err = monr_hrchy_attach_task_event(event);
+exit:
+	monr_hrchy_release_mutexes();
+
+	return err;
+}
+
+/**
+ * __match_event() - Determine if @a and @b should share a rmid.
+ */
+static bool __match_event(struct perf_event *a, struct perf_event *b)
+{
+	/* Cgroup/non-task per-cpu and task events don't mix */
+	if ((a->attach_state & PERF_ATTACH_TASK) !=
+	    (b->attach_state & PERF_ATTACH_TASK))
+		return false;
+
+#ifdef CONFIG_CGROUP_PERF
+	if (a->cgrp != b->cgrp)
+		return false;
+#endif
+
+	/* If not task event, it's a a cgroup or a non-task cpu event. */
+	if (!(b->attach_state & PERF_ATTACH_TASK))
+		return true;
+
+	/* Events that target same task are placed into the same group. */
+	if (a->hw.target == b->hw.target)
+		return true;
+
+	/* Are we a inherited event? */
+	if (b->parent == a)
+		return true;
+
+	return false;
+}
+
 static struct pmu intel_cmt_pmu;
 
+/* Try to find a monr with same target, otherwise create new one. */
+static int mon_group_setup_event(struct perf_event *event)
+{
+	struct monr *monr;
+	int err;
+
+	lockdep_assert_held(&cmt_mutex);
+
+	list_for_each_entry(monr, &cmt_event_monrs, entry) {
+		if (!__match_event(monr->mon_events, event))
+			continue;
+		monr_hrchy_acquire_mutexes();
+		err = monr_append_event(monr, event);
+		monr_hrchy_release_mutexes();
+		return err;
+	}
+	/*
+	 * Since no match was found, create a new monr and set this
+	 * event as head of a mon_group. All events in this group
+	 * will share the monr.
+	 */
+	return monr_hrchy_attach_event(event);
+}
+
 static void intel_cmt_event_read(struct perf_event *event)
 {
 }
@@ -68,6 +272,20 @@ static int intel_cmt_event_add(struct perf_event *event, int mode)
 	return 0;
 }
 
+static void intel_cmt_event_destroy(struct perf_event *event)
+{
+	struct monr *monr;
+
+	mutex_lock(&cmt_mutex);
+	monr_hrchy_acquire_mutexes();
+
+	/* monr is dettached from event. */
+	monr = monr_remove_event(event);
+
+	monr_hrchy_release_mutexes();
+	mutex_unlock(&cmt_mutex);
+}
+
 static int intel_cmt_event_init(struct perf_event *event)
 {
 	int err = 0;
@@ -88,6 +306,16 @@ static int intel_cmt_event_init(struct perf_event *event)
 	    event->attr.sample_period) /* no sampling */
 		return -EINVAL;
 
+	event->destroy = intel_cmt_event_destroy;
+
+	INIT_LIST_HEAD(&event->hw.cmt_list);
+
+	mutex_lock(&cmt_mutex);
+
+	err = mon_group_setup_event(event);
+
+	mutex_unlock(&cmt_mutex);
+
 	return err;
 }
 
diff --git a/arch/x86/events/intel/cmt.h b/arch/x86/events/intel/cmt.h
index 55416db..0ce5d4d 100644
--- a/arch/x86/events/intel/cmt.h
+++ b/arch/x86/events/intel/cmt.h
@@ -3,6 +3,12 @@
  * (formerly Intel Cache QoS Monitoring, CQM)
  *
  *
+ * A "Monitored Resource" (monr) is the entity monitored by CMT and MBM.
+ * In order to monitor a cgroups and/or thread, it must be associated to
+ * a monr. A monr is active in a CPU when a thread that is associated to
+ * it (either directly or through a cgroup) is scheduled in it.
+ *
+ *
  * Locking
  *
  * One global cmt_mutex. One mutex and spin_lock per package.
@@ -35,3 +41,17 @@ struct pkg_data {
 	u32			max_rmid;
 	u16			pkgid;
 };
+
+/**
+ * struct monr - MONitored Resource.
+ * @mon_events:		The head of event's group that use this monr, if any.
+ * @entry:		List entry into cmt_event_monrs.
+ *
+ * An monr is assigned to every CMT event and/or monitored cgroups when
+ * monitoring is activated and that instance's address do not change during
+ * the lifetime of the event or cgroup.
+ */
+struct monr {
+	struct perf_event		*mon_events;
+	struct list_head		entry;
+};
-- 
2.8.0.rc3.226.g39d4020