powerpc/perf/hv-24x7: Dont create sysfs event files for dummy events

The hv_24x7 performance monitoring unit creates a list of supported
events from the event catalog obtained via HCALL. The hv_24x7 catalog
could also contain invalid or dummy events with names like RESERVED*.
These events do not have any hardware counters backing them. Add a
check to string compare the event names to filter such events out.

Result on power9 machine:

Before this patch:
  .....
  hv_24x7/PM_XLINK2_OUT_ODD_CYC,chip=?/              [Kernel PMU event]
  hv_24x7/PM_XLINK2_OUT_ODD_DATA_COUNT,chip=?/       [Kernel PMU event]
  hv_24x7/PM_XLINK2_OUT_ODD_TOTAL_UTIL,chip=?/       [Kernel PMU event]
  hv_24x7/PM_XTS_ATR_DEMAND_CHECKOUT,chip=?/         [Kernel PMU event]
  hv_24x7/PM_XTS_ATR_DEMAND_CHECKOUT_MISS,chip=?/    [Kernel PMU event]
  hv_24x7/PM_XTS_ATSD_SENT,chip=?/                   [Kernel PMU event]
  hv_24x7/PM_XTS_ATSD_TLBI_RCV,chip=?/               [Kernel PMU event]
  hv_24x7/RESERVED_NEST1,chip=?/                     [Kernel PMU event]
  hv_24x7/RESERVED_NEST10,chip=?/                    [Kernel PMU event]
  hv_24x7/RESERVED_NEST11,chip=?/                    [Kernel PMU event]
  hv_24x7/RESERVED_NEST12,chip=?/                    [Kernel PMU event]
  hv_24x7/RESERVED_NEST13,chip=?/                    [Kernel PMU event]
  ......

dmesg:
  [    0.000362] printk: console [hvc0] enabled
  [    0.815452] hv-24x7: read 1530 catalog entries, created 537 event attrs (0 failures), 275 descs

After this patch:
  ......
  hv_24x7/PM_XLINK2_OUT_ODD_AVLBL_CYC,chip=?/        [Kernel PMU event]
  hv_24x7/PM_XLINK2_OUT_ODD_CYC,chip=?/              [Kernel PMU event]
  hv_24x7/PM_XLINK2_OUT_ODD_DATA_COUNT,chip=?/       [Kernel PMU event]
  hv_24x7/PM_XLINK2_OUT_ODD_TOTAL_UTIL,chip=?/       [Kernel PMU event]
  hv_24x7/PM_XTS_ATR_DEMAND_CHECKOUT,chip=?/         [Kernel PMU event]
  hv_24x7/PM_XTS_ATR_DEMAND_CHECKOUT_MISS,chip=?/    [Kernel PMU event]
  hv_24x7/PM_XTS_ATSD_SENT,chip=?/                   [Kernel PMU event]
  hv_24x7/PM_XTS_ATSD_TLBI_RCV,chip=?/               [Kernel PMU event]
  hv_24x7/TOD,chip=?/                                [Kernel PMU event]
  ......

dmesg:
  [    0.000357] printk: console [hvc0] enabled
  [    0.808592] hv-24x7: read 1530 catalog entries, created 509 event attrs (0 failures), 275 descs
Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
[mpe: Simplify ignore_event(), minor change log formatting]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201228085204.18026-1-kjain@linux.ibm.com

arch/powerpc/perf/hv-24x7.c

@@ -764,6 +764,14 @@ static ssize_t catalog_event_len_validate(struct hv_24x7_event_data *event,
 	return ev_len;
 }
 
+/*
+ * Return true incase of invalid or dummy events with names like RESERVED*
+ */
+static bool ignore_event(const char *name)
+{
+	return strncmp(name, "RESERVED", 8) == 0;
+}
+
 #define MAX_4K (SIZE_MAX / 4096)
 
 static int create_events_from_catalog(struct attribute ***events_,
@@ -894,6 +902,10 @@ static int create_events_from_catalog(struct attribute ***events_,
 
 		name = event_name(event, &nl);
 
+		if (ignore_event(name)) {
+			junk_events++;
+			continue;
+		}
 		if (event->event_group_record_len == 0) {
 			pr_devel("invalid event %zu (%.*s): group_record_len == 0, skipping\n",
 					event_idx, nl, name);
@@ -955,6 +967,9 @@ static int create_events_from_catalog(struct attribute ***events_,
 			continue;
 
 		name  = event_name(event, &nl);
+		if (ignore_event(name))
+			continue;
+
 		nonce = event_uniq_add(&ev_uniq, name, nl, event->domain);
 		ct    = event_data_to_attrs(event_idx, events + event_attr_ct,
 					    event, nonce);