s390/pai: change sampling event assignment for PMU device driver

Currently only one PAI sampling event can be created and active
at any one time. The PMU device drivers store a pointer to this
event in their data structures even when the event is created
for counting and the PMU device driver reference to this counting
event is never needed.
Change this and assign the pointer to the PMU device driver
only when a sampling event is created.

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Acked-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/kernel/perf_pai_crypto.c

@@ -324,12 +324,15 @@ static void paicrypt_read(struct perf_event *event)
 
 static void paicrypt_start(struct perf_event *event, int flags)
 {
+	struct paicrypt_mapptr *mp = this_cpu_ptr(paicrypt_root.mapptr);
+	struct paicrypt_map *cpump = mp->mapptr;
 	u64 sum;
 
 	if (!event->attr.sample_period) {	/* Counting */
 		sum = paicrypt_getall(event);	/* Get current value */
 		local64_set(&event->hw.prev_count, sum);
 	} else {				/* Sampling */
+		cpump->event = event;
 		perf_sched_cb_inc(event->pmu);
 	}
 }
@@ -345,7 +348,6 @@ static int paicrypt_add(struct perf_event *event, int flags)
 		WRITE_ONCE(S390_lowcore.ccd, ccd);
 		local_ctl_set_bit(0, CR0_CRYPTOGRAPHY_COUNTER_BIT);
 	}
-	cpump->event = event;
 	if (flags & PERF_EF_START)
 		paicrypt_start(event, PERF_EF_RELOAD);
 	event->hw.state = 0;

arch/s390/kernel/perf_pai_ext.c

@@ -203,7 +203,6 @@ static int paiext_alloc(struct perf_event_attr *a, struct perf_event *event)
 	}
 
 	rc = 0;
-	cpump->event = event;
 
 undo:
 	if (rc) {
@@ -328,12 +327,15 @@ static void paiext_read(struct perf_event *event)
 
 static void paiext_start(struct perf_event *event, int flags)
 {
+	struct paiext_mapptr *mp = this_cpu_ptr(paiext_root.mapptr);
+	struct paiext_map *cpump = mp->mapptr;
 	u64 sum;
 
 	if (!event->attr.sample_period) {	/* Counting */
 		sum = paiext_getall(event);	/* Get current value */
 		local64_set(&event->hw.prev_count, sum);
 	} else {				/* Sampling */
+		cpump->event = event;
 		perf_sched_cb_inc(event->pmu);
 	}
 }
@@ -352,7 +354,6 @@ static int paiext_add(struct perf_event *event, int flags)
 		debug_sprintf_event(paiext_dbg, 4, "%s 1508 %llx acc %llx\n",
 				    __func__, S390_lowcore.aicd, pcb->acc);
 	}
-	cpump->event = event;
 	if (flags & PERF_EF_START)
 		paiext_start(event, PERF_EF_RELOAD);
 	event->hw.state = 0;