[PATCH 5.15 079/171] perf intel-pt: Fix state setting when receiving overflow (OVF) packet

Greg Kroah-Hartman
2021-12-13T10:21:26Z

From: Adrian Hunter <adrian.hunter@intel.com>

commit c79ee2b2160909889df67c8801352d3e69d43a1a upstream.

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")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: stable@vger.kernel.org # v5.15+
Link: https://lore.kernel.org/r/20211210162303.2288710-5-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
tools/perf/util/intel-pt-decoder/intel-pt-decoder.c | 32 +++++++++++++++++---
1 file changed, 28 insertions(+), 4 deletions(-)

--- a/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
+++ b/tools/perf/util/intel-pt-decoder/intel-pt-decoder.c
@@ -1248,6 +1248,20 @@ static bool intel_pt_fup_event(struct in
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;
@@ -1601,7 +1615,16 @@ static int intel_pt_overflow(struct inte
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;
}
@@ -2956,6 +2979,7 @@ next:

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) {
@@ -3461,10 +3485,10 @@ static int intel_pt_sync_ip(struct intel
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;
}
@@ -3479,7 +3503,6 @@ static int intel_pt_sync_ip(struct intel
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;
@@ -3698,7 +3721,8 @@ const struct intel_pt_state *intel_pt_de

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);