Re: [PATCH v5 06/17] perf: cs-etm: Support version 0.1 of HW_ID packets

[James Clark <james.clark@linaro.org>]

On 18/07/2024 2:24 pm, Mike Leach wrote:
> On Fri, 12 Jul 2024 at 11:22, James Clark <james.clark@linaro.org> wrote:
>>
>> From: James Clark <james.clark@arm.com>
>>
>> v0.1 HW_ID packets have a new field that describes which sink each CPU
>> writes to. Use the sink ID to link trace ID maps to each other so that
>> mappings are shared wherever the sink is shared.
>>
>> Also update the error message to show that overlapping IDs aren't an
>> error in per-thread mode, just not supported. In the future we can
>> use the CPU ID from the AUX records, or watch for changing sink IDs on
>> HW_ID packets to use the correct decoders.
>>
>> Signed-off-by: James Clark <james.clark@arm.com>
>> Signed-off-by: James Clark <james.clark@linaro.org>
>> ---
>>   tools/include/linux/coresight-pmu.h |  17 +++--
>>   tools/perf/util/cs-etm.c            | 100 +++++++++++++++++++++++++---
>>   2 files changed, 103 insertions(+), 14 deletions(-)
>>
>> diff --git a/tools/include/linux/coresight-pmu.h b/tools/include/linux/coresight-pmu.h
>> index 51ac441a37c3..89b0ac0014b0 100644
>> --- a/tools/include/linux/coresight-pmu.h
>> +++ b/tools/include/linux/coresight-pmu.h
>> @@ -49,12 +49,21 @@
>>    * Interpretation of the PERF_RECORD_AUX_OUTPUT_HW_ID payload.
>>    * Used to associate a CPU with the CoreSight Trace ID.
>>    * [07:00] - Trace ID - uses 8 bits to make value easy to read in file.
>> - * [59:08] - Unused (SBZ)
>> - * [63:60] - Version
>> + * [39:08] - Sink ID - as reported in /sys/bus/event_source/devices/cs_etm/sinks/
>> + *           Added in minor version 1.
>> + * [55:40] - Unused (SBZ)
>> + * [59:56] - Minor Version - previously existing fields are compatible with
>> + *           all minor versions.
>> + * [63:60] - Major Version - previously existing fields mean different things
>> + *           in new major versions.
>>    */
>>   #define CS_AUX_HW_ID_TRACE_ID_MASK     GENMASK_ULL(7, 0)
>> -#define CS_AUX_HW_ID_VERSION_MASK      GENMASK_ULL(63, 60)
>> +#define CS_AUX_HW_ID_SINK_ID_MASK      GENMASK_ULL(39, 8)
>>
>> -#define CS_AUX_HW_ID_CURR_VERSION 0
>> +#define CS_AUX_HW_ID_MINOR_VERSION_MASK        GENMASK_ULL(59, 56)
>> +#define CS_AUX_HW_ID_MAJOR_VERSION_MASK        GENMASK_ULL(63, 60)
>> +
>> +#define CS_AUX_HW_ID_MAJOR_VERSION 0
>> +#define CS_AUX_HW_ID_MINOR_VERSION 1
>>
>>   #endif
>> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
>> index 954a6f7bedf3..87e983da19be 100644
>> --- a/tools/perf/util/cs-etm.c
>> +++ b/tools/perf/util/cs-etm.c
>> @@ -118,6 +118,12 @@ struct cs_etm_queue {
>>          struct cs_etm_traceid_queue **traceid_queues;
>>          /* Conversion between traceID and metadata pointers */
>>          struct intlist *traceid_list;
>> +       /*
>> +        * Same as traceid_list, but traceid_list may be a reference to another
>> +        * queue's which has a matching sink ID.
>> +        */
>> +       struct intlist *own_traceid_list;
>> +       u32 sink_id;
>>   };
>>
>>   static int cs_etm__process_timestamped_queues(struct cs_etm_auxtrace *etm);
>> @@ -142,6 +148,7 @@ static int cs_etm__metadata_set_trace_id(u8 trace_chan_id, u64 *cpu_metadata);
>>                        (queue_nr << 16 | trace_chan_id)
>>   #define TO_QUEUE_NR(cs_queue_nr) (cs_queue_nr >> 16)
>>   #define TO_TRACE_CHAN_ID(cs_queue_nr) (cs_queue_nr & 0x0000ffff)
>> +#define SINK_UNSET ((u32) -1)
>>
>>   static u32 cs_etm__get_v7_protocol_version(u32 etmidr)
>>   {
>> @@ -241,7 +248,16 @@ static int cs_etm__insert_trace_id_node(struct cs_etm_queue *etmq,
>>                  int err;
>>
>>                  if (curr_cpu_data[CS_ETM_CPU] != cpu_metadata[CS_ETM_CPU]) {
>> -                       pr_err("CS_ETM: map mismatch between HW_ID packet CPU and Trace ID\n");
>> +                       /*
>> +                        * With > CORESIGHT_TRACE_IDS_MAX ETMs, overlapping IDs
>> +                        * are expected (but not supported) in per-thread mode,
>> +                        * rather than signifying an error.
>> +                        */
>> +                       if (etmq->etm->per_thread_decoding)
>> +                               pr_err("CS_ETM: overlapping Trace IDs aren't currently supported in per-thread mode\n");
>> +                       else
>> +                               pr_err("CS_ETM: map mismatch between HW_ID packet CPU and Trace ID\n");
>> +
>>                          return -EINVAL;
>>                  }
>>
>> @@ -326,6 +342,64 @@ static int cs_etm__process_trace_id_v0(struct cs_etm_auxtrace *etm, int cpu,
>>          return cs_etm__metadata_set_trace_id(trace_chan_id, cpu_data);
>>   }
>>
>> +static int cs_etm__process_trace_id_v0_1(struct cs_etm_auxtrace *etm, int cpu,
>> +                                        u64 hw_id)
>> +{
>> +       struct cs_etm_queue *etmq = cs_etm__get_queue(etm, cpu);
>> +       int ret;
>> +       u64 *cpu_data;
>> +       u32 sink_id = FIELD_GET(CS_AUX_HW_ID_SINK_ID_MASK, hw_id);
>> +       u8 trace_id = FIELD_GET(CS_AUX_HW_ID_TRACE_ID_MASK, hw_id);
>> +
>> +       /*
>> +        * Check sink id hasn't changed in per-cpu mode. In per-thread mode,
>> +        * let it pass for now until an actual overlapping trace ID is hit. In
>> +        * most cases IDs won't overlap even if the sink changes.
>> +        */
>> +       if (!etmq->etm->per_thread_decoding && etmq->sink_id != SINK_UNSET &&
>> +           etmq->sink_id != sink_id) {
>> +               pr_err("CS_ETM: mismatch between sink IDs\n");
>> +               return -EINVAL;
>> +       }
>> +
>> +       etmq->sink_id = sink_id;
>> +
>> +       /* Find which other queues use this sink and link their ID maps */
>> +       for (unsigned int i = 0; i < etm->queues.nr_queues; ++i) {
>> +               struct cs_etm_queue *other_etmq = etm->queues.queue_array[i].priv;
>> +
>> +               /* Different sinks, skip */
>> +               if (other_etmq->sink_id != etmq->sink_id)
>> +                       continue;
>> +
>> +               /* Already linked, skip */
>> +               if (other_etmq->traceid_list == etmq->traceid_list)
>> +                       continue;
>> +
>> +               /* At the point of first linking, this one should be empty */
>> +               if (!intlist__empty(etmq->traceid_list)) {
>> +                       pr_err("CS_ETM: Can't link populated trace ID lists\n");
>> +                       return -EINVAL;
>> +               }
>> +
>> +               etmq->own_traceid_list = NULL;
>> +               intlist__delete(etmq->traceid_list);
>> +               etmq->traceid_list = other_etmq->traceid_list;
>> +               break;
>> +       }
>> +
>> +       cpu_data = get_cpu_data(etm, cpu);
>> +       ret = cs_etm__insert_trace_id_node(etmq, trace_id, cpu_data);
>> +       if (ret)
>> +               return ret;
>> +
>> +       ret = cs_etm__metadata_set_trace_id(trace_id, cpu_data);
>> +       if (ret)
>> +               return ret;
>> +
>> +       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];
>> @@ -414,10 +488,10 @@ static int cs_etm__process_aux_output_hw_id(struct perf_session *session,
>>
>>          /* 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);
>> +       version = FIELD_GET(CS_AUX_HW_ID_MAJOR_VERSION_MASK, hw_id);
>>
>>          /* check that we can handle this version */
>> -       if (version > CS_AUX_HW_ID_CURR_VERSION) {
>> +       if (version > CS_AUX_HW_ID_MAJOR_VERSION) {
>>                  pr_err("CS ETM Trace: PERF_RECORD_AUX_OUTPUT_HW_ID version %d not supported. Please update Perf.\n",
>>                         version);
>>                  return -EINVAL;
>> @@ -442,7 +516,10 @@ static int cs_etm__process_aux_output_hw_id(struct perf_session *session,
>>                  return -EINVAL;
>>          }
>>
>> -       return cs_etm__process_trace_id_v0(etm, cpu, hw_id);
> 
> Perhaps leave this as the final statement of the function
> 
>> +       if (FIELD_GET(CS_AUX_HW_ID_MINOR_VERSION_MASK, hw_id) == 0)
> 
> this could be moved before and be
> 
> if (FIELD_GET(CS_AUX_HW_ID_MINOR_VERSION_MASK, hw_id) == 1)
>                 return cs_etm__process_trace_id_v0_1(etm, cpu, hw_id);
> 
> 

Because I was intending minor version changes to be backwards compatible 
I have it so that any value other than 0 is treated as v0.1. Otherwise 
version updates will break old versions of Perf. And then if we added a 
v0.3 it would look like this:

  if (FIELD_GET(CS_AUX_HW_ID_MINOR_VERSION_MASK, hw_id) == 0)
    return cs_etm__process_trace_id_v0(etm, cpu, hw_id);
  else if (FIELD_GET(CS_AUX_HW_ID_MINOR_VERSION_MASK, hw_id) == 1)
    return cs_etm__process_trace_id_v0_1(etm, cpu, hw_id);
  else
    return cs_etm__process_trace_id_v0_2(etm, cpu, hw_id);

Based on that I'm not sure if you still think it should be changed?