linux-kernel - [PATCH 4/7] perf intel-pt: Fix overflow state

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Message-Id: <20211210162303.2288710-5-adrian.hunter@intel.com>
Date:   Fri, 10 Dec 2021 18:23:00 +0200
From:   Adrian Hunter <adrian.hunter@...el.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Jiri Olsa <jolsa@...hat.com>, linux-kernel@...r.kernel.org
Subject: [PATCH 4/7] perf intel-pt: Fix overflow state

An overflow (OVF packet) is treated as an error because it represents a
loss of trace data, but there is no loss of synchronization, so the packet
state should be INTEL_PT_STATE_IN_SYNC not INTEL_PT_STATE_ERR_RESYNC.
To support that, some additional variables must be reset, and the FUP
packet that may follow OVF is treated as an FUP event.

Fixes: f4aa081949e7b6 ("perf tools: Add Intel PT decoder")
Cc: stable@...r.kernel.org # v5.15+
Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
---
 .../util/intel-pt-decoder/intel-pt-decoder.c  | 32 ++++++++++++++++---
 1 file changed, 28 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
index 16fbbf07e367..845b0ca866a4 100644
--- a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
+++ b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
@@ -1249,6 +1249,20 @@ static bool intel_pt_fup_event(struct intel_pt_decoder *decoder)
 		decoder->state.type |= INTEL_PT_BLK_ITEMS;
 		ret = true;
 	}
+	if (decoder->overflow) {
+		decoder->overflow = false;
+		if (!ret && !decoder->pge) {
+			if (decoder->hop) {
+				decoder->state.type = 0;
+				decoder->pkt_state = INTEL_PT_STATE_RESAMPLE;
+			}
+			decoder->pge = true;
+			decoder->state.type |= INTEL_PT_BRANCH | INTEL_PT_TRACE_BEGIN;
+			decoder->state.from_ip = 0;
+			decoder->state.to_ip = decoder->ip;
+			return true;
+		}
+	}
 	if (ret) {
 		decoder->state.from_ip = decoder->ip;
 		decoder->state.to_ip = 0;
@@ -1602,7 +1616,16 @@ static int intel_pt_overflow(struct intel_pt_decoder *decoder)
 	intel_pt_clear_tx_flags(decoder);
 	intel_pt_set_nr(decoder);
 	decoder->timestamp_insn_cnt = 0;
-	decoder->pkt_state = INTEL_PT_STATE_ERR_RESYNC;
+	decoder->pkt_state = INTEL_PT_STATE_IN_SYNC;
+	decoder->state.from_ip = decoder->ip;
+	decoder->ip = 0;
+	decoder->pge = false;
+	decoder->set_fup_tx_flags = false;
+	decoder->set_fup_ptw = false;
+	decoder->set_fup_mwait = false;
+	decoder->set_fup_pwre = false;
+	decoder->set_fup_exstop = false;
+	decoder->set_fup_bep = false;
 	decoder->overflow = true;
 	return -EOVERFLOW;
 }
@@ -2957,6 +2980,7 @@ static int intel_pt_walk_trace(struct intel_pt_decoder *decoder)
 
 		case INTEL_PT_TIP_PGE: {
 			decoder->pge = true;
+			decoder->overflow = false;
 			intel_pt_mtc_cyc_cnt_pge(decoder);
 			intel_pt_set_nr(decoder);
 			if (decoder->packet.count == 0) {
@@ -3462,10 +3486,10 @@ static int intel_pt_sync_ip(struct intel_pt_decoder *decoder)
 	decoder->set_fup_pwre = false;
 	decoder->set_fup_exstop = false;
 	decoder->set_fup_bep = false;
+	decoder->overflow = false;
 
 	if (!decoder->branch_enable) {
 		decoder->pkt_state = INTEL_PT_STATE_IN_SYNC;
-		decoder->overflow = false;
 		decoder->state.type = 0; /* Do not have a sample */
 		return 0;
 	}
@@ -3480,7 +3504,6 @@ static int intel_pt_sync_ip(struct intel_pt_decoder *decoder)
 		decoder->pkt_state = INTEL_PT_STATE_RESAMPLE;
 	else
 		decoder->pkt_state = INTEL_PT_STATE_IN_SYNC;
-	decoder->overflow = false;
 
 	decoder->state.from_ip = 0;
 	decoder->state.to_ip = decoder->ip;
@@ -3699,7 +3722,8 @@ const struct intel_pt_state *intel_pt_decode(struct intel_pt_decoder *decoder)
 
 	if (err) {
 		decoder->state.err = intel_pt_ext_err(err);
-		decoder->state.from_ip = decoder->ip;
+		if (err != -EOVERFLOW)
+			decoder->state.from_ip = decoder->ip;
 		intel_pt_update_sample_time(decoder);
 		decoder->sample_tot_cyc_cnt = decoder->tot_cyc_cnt;
 		intel_pt_set_nr(decoder);
-- 
2.25.1