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Date: Thu, 21 Jul 2022 13:38:14 +0100
From: Mike Leach <mike.leach@...aro.org>
To: James Clark <james.clark@....com>
Cc: mathieu.poirier@...aro.org, peterz@...radead.org, mingo@...hat.com,
acme@...nel.org, linux-perf-users@...r.kernel.org,
quic_jinlmao@...cinc.com, suzuki.poulose@....com,
coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 11/13] perf: cs-etm: Handle PERF_RECORD_AUX_OUTPUT_HW_ID
packet
Hi James
On Wed, 20 Jul 2022 at 17:07, James Clark <james.clark@....com> wrote:
>
>
>
> On 04/07/2022 09:11, Mike Leach wrote:
> > When using dynamically assigned CoreSight trace IDs the drivers can output
> > the ID / CPU association as a PERF_RECORD_AUX_OUTPUT_HW_ID packet.
> >
> > Update cs-etm decoder to handle this packet by setting the CPU/Trace ID
> > mapping.
> >
> > Signed-off-by: Mike Leach <mike.leach@...aro.org>
> > ---
> > tools/include/linux/coresight-pmu.h | 14 ++
> > .../perf/util/cs-etm-decoder/cs-etm-decoder.c | 9 +
> > tools/perf/util/cs-etm.c | 167 +++++++++++++++++-
> > 3 files changed, 185 insertions(+), 5 deletions(-)
> >
> > diff --git a/tools/include/linux/coresight-pmu.h b/tools/include/linux/coresight-pmu.h
> > index 31d007fab3a6..4e8b3148f939 100644
> > --- a/tools/include/linux/coresight-pmu.h
> > +++ b/tools/include/linux/coresight-pmu.h
> > @@ -7,6 +7,8 @@
> > #ifndef _LINUX_CORESIGHT_PMU_H
> > #define _LINUX_CORESIGHT_PMU_H
> >
> > +#include <linux/bits.h>
> > +
> > #define CORESIGHT_ETM_PMU_NAME "cs_etm"
> >
> > /*
> > @@ -40,4 +42,16 @@
> > #define ETM4_CFG_BIT_RETSTK 12
> > #define ETM4_CFG_BIT_VMID_OPT 15
> >
> > +/*
> > + * Interpretation of the PERF_RECORD_AUX_OUTPUT_HW_ID payload.
> > + * Used to associate a CPU with the CoreSight Trace ID.
> > + * [63:16] - unused SBZ
> > + * [15:08] - Trace ID
> > + * [07:00] - Version
> > + */
> > +#define CS_AUX_HW_ID_VERSION_MASK GENMASK_ULL(7, 0)
> > +#define CS_AUX_HW_ID_TRACE_ID_MASK GENMASK_ULL(15, 8)
> > +
> > +#define CS_AUX_HW_ID_CURR_VERSION 0
> > +
> > #endif
> > diff --git a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> > index 31fa3b45134a..d1dd73310707 100644
> > --- a/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> > +++ b/tools/perf/util/cs-etm-decoder/cs-etm-decoder.c
> > @@ -611,6 +611,8 @@ static ocsd_datapath_resp_t cs_etm_decoder__gen_trace_elem_printer(
> > return resp;
> > }
> >
> > +#define CS_TRACE_ID_MASK GENMASK(6, 0)
> > +
> > static int
> > cs_etm_decoder__create_etm_decoder(struct cs_etm_decoder_params *d_params,
> > struct cs_etm_trace_params *t_params,
> > @@ -625,6 +627,7 @@ cs_etm_decoder__create_etm_decoder(struct cs_etm_decoder_params *d_params,
> > switch (t_params->protocol) {
> > case CS_ETM_PROTO_ETMV3:
> > case CS_ETM_PROTO_PTM:
> > + csid = (t_params->etmv3.reg_idr & CS_TRACE_ID_MASK);
> > cs_etm_decoder__gen_etmv3_config(t_params, &config_etmv3);
> > decoder->decoder_name = (t_params->protocol == CS_ETM_PROTO_ETMV3) ?
> > OCSD_BUILTIN_DCD_ETMV3 :
> > @@ -632,11 +635,13 @@ cs_etm_decoder__create_etm_decoder(struct cs_etm_decoder_params *d_params,
> > trace_config = &config_etmv3;
> > break;
> > case CS_ETM_PROTO_ETMV4i:
> > + csid = (t_params->etmv4.reg_traceidr & CS_TRACE_ID_MASK);
> > cs_etm_decoder__gen_etmv4_config(t_params, &trace_config_etmv4);
> > decoder->decoder_name = OCSD_BUILTIN_DCD_ETMV4I;
> > trace_config = &trace_config_etmv4;
> > break;
> > case CS_ETM_PROTO_ETE:
> > + csid = (t_params->ete.reg_traceidr & CS_TRACE_ID_MASK);
> > cs_etm_decoder__gen_ete_config(t_params, &trace_config_ete);
> > decoder->decoder_name = OCSD_BUILTIN_DCD_ETE;
> > trace_config = &trace_config_ete;
> > @@ -645,6 +650,10 @@ cs_etm_decoder__create_etm_decoder(struct cs_etm_decoder_params *d_params,
> > return -1;
> > }
> >
> > + /* if the CPU has no trace ID associated, no decoder needed */
> > + if (csid == CS_UNUSED_TRACE_ID)
> > + return 0;
> > +
> > if (d_params->operation == CS_ETM_OPERATION_DECODE) {
> > if (ocsd_dt_create_decoder(decoder->dcd_tree,
> > decoder->decoder_name,
> > diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> > index df9d67901f8d..ffce858f21fd 100644
> > --- a/tools/perf/util/cs-etm.c
> > +++ b/tools/perf/util/cs-etm.c
> > @@ -217,6 +217,139 @@ static int cs_etm__map_trace_id(u8 trace_chan_id, u64 *cpu_metadata)
> > return 0;
> > }
> >
> > +static int cs_etm__metadata_get_trace_id(u8 *trace_chan_id, u64 *cpu_metadata)
> > +{
> > + u64 cs_etm_magic = cpu_metadata[CS_ETM_MAGIC];
> > +
> > + switch (cs_etm_magic) {
> > + case __perf_cs_etmv3_magic:
> > + *trace_chan_id = cpu_metadata[CS_ETM_ETMTRACEIDR];
> > + break;
> > + case __perf_cs_etmv4_magic:
> > + case __perf_cs_ete_magic:
> > + *trace_chan_id = cpu_metadata[CS_ETMV4_TRCTRACEIDR];
> > + break;
> > +
> > + default:
> > + return -EINVAL;
> > + }
> > + return 0;
> > +}
> > +
> > +static int cs_etm__metadata_set_trace_id(u8 trace_chan_id, u64 *cpu_metadata)
> > +{
> > + u64 cs_etm_magic = cpu_metadata[CS_ETM_MAGIC];
> > +
> > + switch (cs_etm_magic) {
> > + case __perf_cs_etmv3_magic:
> > + cpu_metadata[CS_ETM_ETMTRACEIDR] = trace_chan_id;
> > + break;
> > + case __perf_cs_etmv4_magic:
> > + case __perf_cs_ete_magic:
> > + cpu_metadata[CS_ETMV4_TRCTRACEIDR] = trace_chan_id;
> > + break;
> > +
> > + default:
> > + return -EINVAL;
> > + }
> > + return 0;
> > +}
> > +
> > +/*
> > + * FIELD_GET (linux/bitfield.h) not available outside kernel code,
> > + * and the header contains too many dependencies to just copy over,
> > + * so roll our own based on the original
> > + */
> > +#define __bf_shf(x) (__builtin_ffsll(x) - 1)
> > +#define FIELD_GET(_mask, _reg) \
> > + ({ \
> > + (typeof(_mask))(((_reg) & (_mask)) >> __bf_shf(_mask)); \
> > + })
> > +> +/*
> > + * Handle the PERF_RECORD_AUX_OUTPUT_HW_ID event.
> > + *
> > + * The payload associates the Trace ID and the CPU.
> > + * The routine is tolerant of seeing multiple packets with the same association,
> > + * but a CPU / Trace ID association changing during a session is an error.
> > + */
> > +static int cs_etm__process_aux_output_hw_id(struct perf_session *session,
> > + union perf_event *event)
> > +{
> > + struct cs_etm_auxtrace *etm;
> > + struct perf_sample sample;
> > + struct int_node *inode;
> > + struct evsel *evsel;
> > + u64 *cpu_data;
> > + u64 hw_id;
> > + int cpu, version, err;
> > + u8 trace_chan_id, curr_chan_id;
> > +
> > + /* extract and parse the HW ID */
> > + hw_id = event->aux_output_hw_id.hw_id;
> > + version = FIELD_GET(CS_AUX_HW_ID_VERSION_MASK, hw_id);
> > + trace_chan_id = FIELD_GET(CS_AUX_HW_ID_TRACE_ID_MASK, hw_id);
> > +
> > + /* check that we can handle this version */
> > + if (version > CS_AUX_HW_ID_CURR_VERSION)
> > + return -EINVAL;
> > +
> > + /* get access to the etm metadata */
> > + etm = container_of(session->auxtrace, struct cs_etm_auxtrace, auxtrace);
> > + if (!etm || !etm->metadata)
> > + return -EINVAL;
> > +
> > + /* parse the sample to get the CPU */
> > + evsel = evlist__event2evsel(session->evlist, event);
> > + if (!evsel)
> > + return -EINVAL;
> > + err = evsel__parse_sample(evsel, event, &sample);
> > + if (err)
> > + return err;
> > + cpu = sample.cpu;
> > + if (cpu == -1) {
> > + /* no CPU in the sample - possibly recorded with an old version of perf */
> > + pr_err("CS_ETM: no CPU AUX_OUTPUT_HW_ID sample. Use compatible perf to record.");
> > + return -EINVAL;
> > + }
> > +
> > + /*
> > + * look to see if the metadata contains a valid trace ID.
> > + * if so we mapped it before and it must be the same as the ID in the packet.
> > + */
> > + cpu_data = etm->metadata[cpu];
> > + err = cs_etm__metadata_get_trace_id(&curr_chan_id, cpu_data);
> > + if (err)
> > + return err;
> > + if (CS_IS_VALID_TRACE_ID(curr_chan_id) && (curr_chan_id != trace_chan_id)) {
> > + pr_err("CS_ETM: mismatch between CPU trace ID and HW_ID packet ID\n");
> > + return -EINVAL;
> > + }
> > +
> > + /* next see if the ID is mapped to a CPU, and it matches the current CPU */
> > + inode = intlist__find(traceid_list, trace_chan_id);
> > + if (inode) {
> > + cpu_data = inode->priv;
> > + if ((int)cpu_data[CS_ETM_CPU] != cpu) {
> > + pr_err("CS_ETM: map mismatch between HW_ID packet CPU and Trace ID\n");
> > + return -EINVAL;
> > + }
> > + return 0;
> > + }
> > +
> > + /* not one we've seen before - lets map it */
> > + err = cs_etm__map_trace_id(trace_chan_id, cpu_data);
> > + if (err)
> > + return err;
> > +
> > + /*
> > + * if we are picking up the association from the packet, need to plug
> > + * the correct trace ID into the metadata for setting up decoders later.
> > + */
> > + err = cs_etm__metadata_set_trace_id(trace_chan_id, cpu_data);
> > + return err;
> > +}
> > +
> > void cs_etm__etmq_set_traceid_queue_timestamp(struct cs_etm_queue *etmq,
> > u8 trace_chan_id)
> > {
> > @@ -2433,6 +2566,8 @@ static int cs_etm__process_event(struct perf_session *session,
> > return cs_etm__process_itrace_start(etm, event);
> > else if (event->header.type == PERF_RECORD_SWITCH_CPU_WIDE)
> > return cs_etm__process_switch_cpu_wide(etm, event);
> > + else if (event->header.type == PERF_RECORD_AUX_OUTPUT_HW_ID)
> > + return cs_etm__process_aux_output_hw_id(session, event);
>
> This shouldn't need to be handled here because of the peek at the beginning. Although
> it's probably harmless to do it twice, it can make deciphering the flow quite difficult.
>
Agreed - this was really belt and braces coding while I was testing -
and where PT decoded it.
Given the peek events this can be dropped next time.
> >
> > if (!etm->timeless_decoding && event->header.type == PERF_RECORD_AUX) {
> > /*
> > @@ -2662,7 +2797,7 @@ static void cs_etm__print_auxtrace_info(__u64 *val, int num)
> > for (i = CS_HEADER_VERSION_MAX; cpu < num; cpu++) {
> > if (version == 0)
> > err = cs_etm__print_cpu_metadata_v0(val, &i);
> > - else if (version == 1)
> > + else if (version == 1 || version == 2)
> > err = cs_etm__print_cpu_metadata_v1(val, &i);
> > if (err)
> > return;
> > @@ -2774,11 +2909,16 @@ static int cs_etm__queue_aux_fragment(struct perf_session *session, off_t file_o
> > }
> >
> > /*
> > - * In per-thread mode, CPU is set to -1, but TID will be set instead. See
> > - * auxtrace_mmap_params__set_idx(). Return 'not found' if neither CPU nor TID match.
> > + * In per-thread mode, auxtrace CPU is set to -1, but TID will be set instead. See
> > + * auxtrace_mmap_params__set_idx(). However, the sample AUX event will contain a
> > + * CPU as we set this always for the AUX_OUTPUT_HW_ID event.
> > + * So now compare only TIDs if auxtrace CPU is -1, and CPUs if auxtrace CPU is not -1.
> > + * Return 'not found' if mismatch.
> > */
> > - if ((auxtrace_event->cpu == (__u32) -1 && auxtrace_event->tid != sample->tid) ||
> > - auxtrace_event->cpu != sample->cpu)
> > + if (auxtrace_event->cpu == (__u32) -1) {
> > + if (auxtrace_event->tid != sample->tid)
> > + return 1;
> > + } else if (auxtrace_event->cpu != sample->cpu)
> > return 1;
> >
> > if (aux_event->flags & PERF_AUX_FLAG_OVERWRITE) {
> > @@ -2827,6 +2967,15 @@ static int cs_etm__queue_aux_fragment(struct perf_session *session, off_t file_o
> > return 1;
> > }
> >
> > +static int cs_etm__process_aux_hw_id_cb(struct perf_session *session, union perf_event *event,
> > + u64 offset __maybe_unused, void *data __maybe_unused)
> > +{
> > + /* look to handle PERF_RECORD_AUX_OUTPUT_HW_ID early to ensure decoders can be set up */
> > + if (event->header.type == PERF_RECORD_AUX_OUTPUT_HW_ID)
> > + return cs_etm__process_aux_output_hw_id(session, event);
> > + return 0;
> > +}
>
> I couldn't see the relationship between the two peeks and why they couldn't be done together
> in one pass. I changed it so cs_etm__process_aux_hw_id_cb() is also called on the peek
> to queue the aux records and it seemed to work. At least just opening the file and glancing.
>
> If there is some dependency though, I don't think two passes is excessive.
>
I initially tried this and there are issues.
During testing I had a --per-thread run with two buffers. One buffer
had only a single ID, which appeared as a packet before the buffer was
processed.
The second had the same ID plus a new ID, which appeared after the
first buffer and before the second.
Problem is, under the current system, once data is queued, the
decoders are set and it meant a decoder for the second ID was never
created, resulting in a bunch of undecoded data.
It may well be possible to re-examine how and when decoders are
created, but there is currently a built in assumption that all IDs are
available before the first buffer is queued, and changing this is well
beyond the remit of this patch set.
> > +
> > static int cs_etm__queue_aux_records_cb(struct perf_session *session, union perf_event *event,
> > u64 offset __maybe_unused, void *data __maybe_unused)
> > {
> > @@ -3109,6 +3258,14 @@ int cs_etm__process_auxtrace_info(union perf_event *event,
> > if (err)
> > goto err_delete_thread;
> >
> > + /* scan for AUX_OUTPUT_HW_ID records */
> > + if (hdr_version >= CS_AUX_HW_ID_VERSION_MIN) {
> > + err = perf_session__peek_events(session, session->header.data_offset,
> > + session->header.data_size,
> > + cs_etm__process_aux_hw_id_cb, NULL);
>
> This no longer works at all with piping because of this line in peek_events:
>
> if (perf_data__is_pipe(session->data))
> return -1;
>
Does this not also apply to the:
cs_etm__queue_aux_records(session);
call immediately after this, which also uses perf_session__peek_events()?
> So we should change the warning message to an error and exit earlier:
>
> if (!etm->data_queued)
> pr_warning("CS ETM warning: Coresight decode and TRBE support requires random file access.\n"
> "Continuing with best effort decoding in piped mode.\n\n");
>
> And then we can also remove all the now dead code and variables related to piping like:
>
> etm->data_queued = etm->queues.populated;
> ...
>
> if (!etm->data_queued) {
> ...
> }
>
which means that these were already dead code?
>
> > + if (err)
> > + goto err_delete_thread;
> > + }
> > err = cs_etm__queue_aux_records(session);
> > if (err)
> > goto err_delete_thread;
Regards
Mike
--
Mike Leach
Principal Engineer, ARM Ltd.
Manchester Design Centre. UK
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