linux-kernel - [PATCH v4 16/21] perf arm-spe: Remove size condition checking for events

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Date:   Tue, 27 Oct 2020 11:09:12 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Andre Przywara <andre.przywara@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Wei Li <liwei391@...wei.com>,
        James Clark <james.clark@....com>, Al Grant <Al.Grant@....com>,
        Dave Martin <Dave.Martin@....com>, linux-kernel@...r.kernel.org
Cc:     Leo Yan <leo.yan@...aro.org>
Subject: [PATCH v4 16/21] perf arm-spe: Remove size condition checking for events

In the Armv8 ARM (ARM DDI 0487F.c), chapter "D10.2.6 Events packet", it
describes the event bit is valid with specific payload requirement.  For
example, the Last Level cache access event, the bit is defined as:

  E[8], byte 1 bit [0], when SZ == 0b01 , when SZ == 0b10 ,
  		     or when SZ == 0b11

It requires the payload size is at least 2 bytes, when byte 1 (start
counting from 0) is valid, E[8] (bit 0 in byte 1) can be used for LLC
access event type.  For safety, the code checks the condition for
payload size firstly, if meet the requirement for payload size, then
continue to parse event type.

If review function arm_spe_get_payload(), it has used cast, so any bytes
beyond the valid size have been set to zeros.

For this reason, we don't need to check payload size anymore afterwards
when parse events, thus this patch removes payload size conditions.

Suggested-by: Andre Przywara <andre.przywara@....com>
Signed-off-by: Leo Yan <leo.yan@...aro.org>
Reviewed-by: Andre Przywara <andre.przywara@....com>
---
 .../util/arm-spe-decoder/arm-spe-decoder.c    |  9 ++----
 .../arm-spe-decoder/arm-spe-pkt-decoder.c     | 30 +++++++++----------
 2 files changed, 17 insertions(+), 22 deletions(-)

diff --git a/tools/perf/util/arm-spe-decoder/arm-spe-decoder.c b/tools/perf/util/arm-spe-decoder/arm-spe-decoder.c
index e135ac01d94a..db93e8130916 100644
--- a/tools/perf/util/arm-spe-decoder/arm-spe-decoder.c
+++ b/tools/perf/util/arm-spe-decoder/arm-spe-decoder.c
@@ -196,16 +196,13 @@ static int arm_spe_read_record(struct arm_spe_decoder *decoder)
 			if (payload & BIT(EV_TLB_ACCESS))
 				decoder->record.type |= ARM_SPE_TLB_ACCESS;
 
-			if ((idx == 2 || idx == 4 || idx == 8) &&
-			    (payload & BIT(EV_LLC_MISS)))
+			if (payload & BIT(EV_LLC_MISS))
 				decoder->record.type |= ARM_SPE_LLC_MISS;
 
-			if ((idx == 2 || idx == 4 || idx == 8) &&
-			    (payload & BIT(EV_LLC_ACCESS)))
+			if (payload & BIT(EV_LLC_ACCESS))
 				decoder->record.type |= ARM_SPE_LLC_ACCESS;
 
-			if ((idx == 2 || idx == 4 || idx == 8) &&
-			    (payload & BIT(EV_REMOTE_ACCESS)))
+			if (payload & BIT(EV_REMOTE_ACCESS))
 				decoder->record.type |= ARM_SPE_REMOTE_ACCESS;
 
 			if (payload & BIT(EV_MISPRED))
diff --git a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
index 8e4c4c90eeb0..74f5fcebdc56 100644
--- a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
+++ b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
@@ -317,22 +317,20 @@ static int arm_spe_pkt_desc_event(const struct arm_spe_pkt *packet,
 		if (ret < 0)
 			return ret;
 	}
-	if (packet->index > 1) {
-		if (payload & BIT(EV_LLC_ACCESS)) {
-			ret = arm_spe_pkt_snprintf(&buf, &blen, " LLC-ACCESS");
-			if (ret < 0)
-				return ret;
-		}
-		if (payload & BIT(EV_LLC_MISS)) {
-			ret = arm_spe_pkt_snprintf(&buf, &blen, " LLC-REFILL");
-			if (ret < 0)
-				return ret;
-		}
-		if (payload & BIT(EV_REMOTE_ACCESS)) {
-			ret = arm_spe_pkt_snprintf(&buf, &blen, " REMOTE-ACCESS");
-			if (ret < 0)
-				return ret;
-		}
+	if (payload & BIT(EV_LLC_ACCESS)) {
+		ret = arm_spe_pkt_snprintf(&buf, &blen, " LLC-ACCESS");
+		if (ret < 0)
+			return ret;
+	}
+	if (payload & BIT(EV_LLC_MISS)) {
+		ret = arm_spe_pkt_snprintf(&buf, &blen, " LLC-REFILL");
+		if (ret < 0)
+			return ret;
+	}
+	if (payload & BIT(EV_REMOTE_ACCESS)) {
+		ret = arm_spe_pkt_snprintf(&buf, &blen, " REMOTE-ACCESS");
+		if (ret < 0)
+			return ret;
 	}
 
 	return buf_len - blen;
-- 
2.17.1