s390/pai_crypto: Enable per-task and system-wide sampling event

The PMU for PAI crypto counters enforces the following restrictions:

      - No per-task context for PAI crypto sampling event CRYPTO_ALL
      - No multiple system-wide PAI crypto sampling event CRYPTO_ALL

Both restrictions are removed. One or more per-task sampling events
are supported. Also one or more system-wide sampling events are
supported.

Example for per-task context of sampling event CRYPTO_ALL:
       # perf record -e pai_crypto/CRYPTO_ALL/ -- true
Example for system-wide context of sampling event CRYPTO_ALL:
       # perf record -e pai_crypto/CRYPTO_ALL/ -a -- sleep 4
Acked-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

arch/s390/kernel/perf_pai_crypto.c

@@ -24,6 +24,8 @@ static debug_info_t *cfm_dbg;
 static unsigned int paicrypt_cnt;	/* Size of the mapped counter sets */
 					/* extracted with QPACI instruction */
 
+#define PAI_SWLIST(x)		(&(x)->hw.tp_list)
+
 DEFINE_STATIC_KEY_FALSE(pai_key);
 
 struct pai_userdata {
@@ -36,8 +38,8 @@ struct paicrypt_map {
 	struct pai_userdata *save;	/* Page to store no-zero counters */
 	unsigned int active_events;	/* # of PAI crypto users */
 	refcount_t refcnt;		/* Reference count mapped buffers */
-	enum paievt_mode mode;		/* Type of event */
 	struct perf_event *event;	/* Perf event for sampling */
+	struct list_head syswide_list;	/* List system-wide sampling events */
 };
 
 struct paicrypt_mapptr {
@@ -90,13 +92,10 @@ static void paicrypt_event_destroy_cpu(struct perf_event *event, int cpu)
 	struct paicrypt_map *cpump = mp->mapptr;
 
 	mutex_lock(&pai_reserve_mutex);
-	debug_sprintf_event(cfm_dbg, 5, "%s event %#llx cpu %d users %d"
-			    " mode %d refcnt %u\n", __func__,
-			    event->attr.config, event->cpu,
-			    cpump->active_events, cpump->mode,
+	debug_sprintf_event(cfm_dbg, 5, "%s event %#llx cpu %d users %d "
+			    "refcnt %u\n", __func__, event->attr.config,
+			    event->cpu, cpump->active_events,
 			    refcount_read(&cpump->refcnt));
-	if (event->attr.sample_period)
-		cpump->mode &= ~PAI_MODE_SAMPLING;
 	if (refcount_dec_and_test(&cpump->refcnt)) {
 		debug_sprintf_event(cfm_dbg, 4, "%s page %#lx save %p\n",
 				    __func__, (unsigned long)cpump->page,
@@ -172,12 +171,7 @@ static u64 paicrypt_getall(struct perf_event *event)
 	return sum;
 }
 
-/* Used to avoid races in checking concurrent access of counting and
- * sampling for crypto events
- *
- * Only one instance of event pai_crypto/CRYPTO_ALL/ for sampling is
- * allowed. Several counting events are allowed in parallel.
- *
+/* Check concurrent access of counting and sampling for crypto events.
  * This function is called in process context and it is save to block.
  * When the event initialization functions fails, no other call back will
  * be invoked.
@@ -186,7 +180,6 @@ static u64 paicrypt_getall(struct perf_event *event)
  */
 static struct paicrypt_map *paicrypt_busy(struct perf_event *event, int cpu)
 {
-	struct perf_event_attr *a = &event->attr;
 	struct paicrypt_map *cpump = NULL;
 	struct paicrypt_mapptr *mp;
 	int rc;
@@ -207,25 +200,9 @@ static struct paicrypt_map *paicrypt_busy(struct perf_event *event, int cpu)
 			rc = -ENOMEM;
 			goto free_root;
 		}
+		INIT_LIST_HEAD(&cpump->syswide_list);
 	}
 
-	if (a->sample_period) {		/* Sampling requested */
-		if (cpump->mode & PAI_MODE_SAMPLING)
-			rc = -EBUSY;	/* ... and sampling active */
-		else
-			cpump->mode |= PAI_MODE_SAMPLING;
-	}
-
-	/*
-	 * This error case triggers when there is a conflict:
-	 * Either sampling requested and counting already active, or visa
-	 * versa. Therefore the struct paicrypto_map for this CPU is
-	 * needed or the error could not have occurred. Only adjust root
-	 * node refcount.
-	 */
-	if (rc)
-		goto free_root;
-
 	/* Allocate memory for counter page and counter extraction.
 	 * Only the first counting event has to allocate a page.
 	 */
@@ -250,14 +227,14 @@ static struct paicrypt_map *paicrypt_busy(struct perf_event *event, int cpu)
 	rc = 0;
 	refcount_set(&cpump->refcnt, 1);
 	mp->mapptr = cpump;
-	debug_sprintf_event(cfm_dbg, 5, "%s sample_period %#llx users %d"
-			    " mode %d refcnt %u page %#lx save %p rc %d\n",
-			    __func__, a->sample_period, cpump->active_events,
-			    cpump->mode, refcount_read(&cpump->refcnt),
+	debug_sprintf_event(cfm_dbg, 5, "%s users %d refcnt %u page %#lx "
+			    "save %p rc %d\n", __func__, cpump->active_events,
+			    refcount_read(&cpump->refcnt),
 			    (unsigned long)cpump->page, cpump->save, rc);
 	goto unlock;
 
 free_paicrypt_map:
+	/* Undo memory allocation */
 	kfree(cpump);
 	mp->mapptr = NULL;
 free_root:
@@ -315,11 +292,7 @@ static int paicrypt_event_init(struct perf_event *event)
 	if (a->config < PAI_CRYPTO_BASE ||
 	    a->config > PAI_CRYPTO_BASE + paicrypt_cnt)
 		return -EINVAL;
-	/* Allow only CPU wide operation for sampling */
-	if (a->sample_period &&
-	    ((event->attach_state & PERF_ATTACH_TASK) || event->cpu == -1))
-		return -ENOENT;
-	/* Allow only CRYPTO_ALL for sampling. */
+	/* Allow only CRYPTO_ALL for sampling */
 	if (a->sample_period && a->config != PAI_CRYPTO_BASE)
 		return -EINVAL;
 	/* Get a page to store last counter values for sampling */
@@ -382,9 +355,14 @@ static void paicrypt_start(struct perf_event *event, int flags)
 		sum = paicrypt_getall(event);	/* Get current value */
 		local64_set(&event->hw.prev_count, sum);
 	} else {				/* Sampling */
-		cpump->event = event;
 		memcpy((void *)PAI_SAVE_AREA(event), cpump->page, PAGE_SIZE);
-		perf_sched_cb_inc(event->pmu);
+		/* Enable context switch callback for system-wide sampling */
+		if (!(event->attach_state & PERF_ATTACH_TASK)) {
+			list_add_tail(PAI_SWLIST(event), &cpump->syswide_list);
+			perf_sched_cb_inc(event->pmu);
+		} else {
+			cpump->event = event;
+		}
 	}
 }
 
@@ -405,6 +383,7 @@ static int paicrypt_add(struct perf_event *event, int flags)
 	return 0;
 }
 
+static void paicrypt_have_sample(struct perf_event *, struct paicrypt_map *);
 static void paicrypt_stop(struct perf_event *event, int flags)
 {
 	struct paicrypt_mapptr *mp = this_cpu_ptr(paicrypt_root.mapptr);
@@ -413,8 +392,13 @@ static void paicrypt_stop(struct perf_event *event, int flags)
 	if (!event->attr.sample_period) {	/* Counting */
 		paicrypt_read(event);
 	} else {				/* Sampling */
-		perf_sched_cb_dec(event->pmu);
-		cpump->event = NULL;
+		if (!(event->attach_state & PERF_ATTACH_TASK)) {
+			perf_sched_cb_dec(event->pmu);
+			list_del(PAI_SWLIST(event));
+		} else {
+			paicrypt_have_sample(event, cpump);
+			cpump->event = NULL;
+		}
 	}
 	event->hw.state = PERF_HES_STOPPED;
 }
@@ -507,23 +491,30 @@ static int paicrypt_push_sample(size_t rawsize, struct paicrypt_map *cpump,
 }
 
 /* Check if there is data to be saved on schedule out of a task. */
-static int paicrypt_have_sample(void)
+static void paicrypt_have_sample(struct perf_event *event,
+				 struct paicrypt_map *cpump)
 {
-	struct paicrypt_mapptr *mp = this_cpu_ptr(paicrypt_root.mapptr);
-	struct paicrypt_map *cpump = mp->mapptr;
-	struct perf_event *event = cpump->event;
 	size_t rawsize;
-	int rc = 0;
 
 	if (!event)		/* No event active */
-		return 0;
+		return;
 	rawsize = paicrypt_copy(cpump->save, cpump->page,
 				(unsigned long *)PAI_SAVE_AREA(event),
-				cpump->event->attr.exclude_user,
-				cpump->event->attr.exclude_kernel);
+				event->attr.exclude_user,
+				event->attr.exclude_kernel);
 	if (rawsize)			/* No incremented counters */
-		rc = paicrypt_push_sample(rawsize, cpump, event);
-	return rc;
+		paicrypt_push_sample(rawsize, cpump, event);
+}
+
+/* Check if there is data to be saved on schedule out of a task. */
+static void paicrypt_have_samples(void)
+{
+	struct paicrypt_mapptr *mp = this_cpu_ptr(paicrypt_root.mapptr);
+	struct paicrypt_map *cpump = mp->mapptr;
+	struct perf_event *event;
+
+	list_for_each_entry(event, &cpump->syswide_list, hw.tp_list)
+		paicrypt_have_sample(event, cpump);
 }
 
 /* Called on schedule-in and schedule-out. No access to event structure,
@@ -535,7 +526,7 @@ static void paicrypt_sched_task(struct perf_event_pmu_context *pmu_ctx, bool sch
 	 * results on schedule_out and if page was dirty, save old values.
 	 */
 	if (!sched_in)
-		paicrypt_have_sample();
+		paicrypt_have_samples();
 }
 
 /* Attribute definitions for paicrypt interface. As with other CPU