[PATCH V2 0/6] tools/perf: Add powerpc HTM auxtrace support

[Athira Rajeev <atrajeev@linux.ibm.com>]

Overview:
This series adds perf tool support for capturing and processing Hardware
Trace Macro (HTM) trace data on POWER systems.  HTM exposes raw bus-trace
data via the H_HTM hypervisor call.  The kernel-side HTM PMU driver
(submitted separately) streams this data into perf AUX buffers and emits
memory configuration as PERF_SAMPLE_RAW records.

This series wires up the record and report sides in the perf tool so that
'perf record' collects HTM data and 'perf report' writes the trace and
memory configuration to files ready for post-processing with htmdecoder.

Patch overview:
Patch 1 refactors the existing powerpc auxtrace dispatch.  All VPA-DTL
recording logic is moved from arch/powerpc/util/auxtrace.c into its own
file, arch/powerpc/util/vpa-dtl.c, leaving auxtrace_record__init() as a
thin per-PMU dispatcher.  This is a prerequisite for adding the HTM
recording path cleanly.

Patch 2 adds the HTM recording path (arch/powerpc/util/htm.c and
util/powerpc-htm.h).  htm_recording_init() sets up the auxtrace_record
callbacks.  htm_info_fill() stores the PMU type and a (cpu, attr.config)
pair for each htm evsel into the PERF_RECORD_AUXTRACE_INFO priv[] area.
The decode side reads these back to map each AUX buffer to its
(node, chip, core) target using event->auxtrace.cpu.  PERF_SAMPLE_RAW is
also enabled here so that memory configuration records are captured
alongside the AUX stream.

Patch 3 adds a generic weak arch_perf_record__need_read() hook in
builtin-record.c.  When the hook returns non-zero, perf record performs
an extra mmap-read pass before disabling events.  The drain loop runs
until the hook returns 0 or no forward progress is made, then the events
are disabled and closed normally.

Patch 4 implements arch_perf_record__need_read() for powerpc.  It reads
event->count for all open htm evsels via perf_evsel__read() and
accumulates the values.  The kernel driver sets this count to 1 while
data is staged in its internal buffers and to 0 once the stream is
exhausted.  A non-zero total causes the recording loop to perform another
read pass.

Patch 5 adds PERF_AUXTRACE_POWERPC_HTM to the auxtrace_type enum and
wires the dispatch in perf_event__process_auxtrace_info().  It also
amends htm_info_fill() to set auxtrace_info->type now that the constant
is available.

Patch 6 adds the full HTM decode path in util/powerpc-htm.c.
powerpc_htm_process_auxtrace_info() reads the (cpu, config) pairs from
priv[] and builds a cpu_configs[] lookup table.  As each
PERF_RECORD_AUXTRACE event arrives, process_auxtrace_event() maps it to
the correct target and writes the data to htm.bin.nX.pX.cX immediately.
PERF_RECORD_SAMPLE RAW records are written to translation.nX.pX.cX by
process_event().  Per-run first-write tracking (htm_target_seen) ensures
O_TRUNC on the first write and O_APPEND on subsequent writes.

Patches not included in V2:
Three patches present in V1 are intentionally dropped from this series
and will be submitted as a follow-on once the core infrastructure gets
integrated:

  - htmdecode integration: V1 patch 6 invoked the external htmdecode
    tool via fork/exec after writing htm.bin.* to decode the raw
    bus-trace data in-process.  This is deferred because the interface
    between perf and an external decode tool needs more discussion.

  - Physical-to-logical address mapping: V1 patch 7 read the current
    partition ID and parsed the translation.*

  - Synthetic sample generation: V1 patches 8 and 9 created a
    PERF_TYPE_SYNTH event named "htm", injected synthetic perf samples

Usage example:
Collect HTM trace data from a single chip target:

  # perf record -C 9 -m,256 \
      -e htm/nodalchipindex=2,nodeindex=0,htm_type=1/ sleep 3
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 256.277 MB perf.data ]

  # perf report

Output files written by perf report:

  htm.bin.n0.p2.c0       raw HTM bus-trace data
  translation.n0.p2.c0   memory configuration records

Multiple targets can be collected simultaneously:

  # perf record -m,256 \
      -e htm/nodalchipindex=2,nodeindex=0,htm_type=1,cpu=8/ \
      -e htm/nodalchipindex=1,nodeindex=0,htm_type=1,cpu=9/ \
      -a sleep 10

Testing:
Tested on POWER10.  Both htm.bin.* and translation.* files are produced
correctly for single and dual target collection.

Note: Link to kernel patches:
https://lore.kernel.org/linuxppc-dev/20260720104447.11843-1-atrajeev@linux.ibm.com/T/#t

Athira Rajeev (6):
  tools/perf: Move powerpc VPA-DTL auxtrace init into a separate file
  tools/perf: Add AUXTRACE recording support for powerpc HTM
  tools/perf: Add arch hook to drain remaining data before event close
  tools/perf: Add powerpc callback support for
    arch_perf_record__need_read
  tools/perf: Add powerpc HTM auxtrace event processing support
  tools/perf: Add perf tool support for processing powerpc HTM AUXTRACE
    records

 tools/perf/arch/powerpc/util/Build      |   2 +
 tools/perf/arch/powerpc/util/auxtrace.c |  93 +-----
 tools/perf/arch/powerpc/util/evsel.c    |  69 ++++
 tools/perf/arch/powerpc/util/htm.c      | 169 ++++++++++
 tools/perf/arch/powerpc/util/vpa-dtl.c  |  95 ++++++
 tools/perf/builtin-record.c             |  45 +++
 tools/perf/util/Build                   |   1 +
 tools/perf/util/auxtrace.c              |   4 +
 tools/perf/util/auxtrace.h              |   1 +
 tools/perf/util/powerpc-htm.c           | 415 ++++++++++++++++++++++++
 tools/perf/util/powerpc-htm.h           |  43 +++
 tools/perf/util/powerpc-vpadtl.h        |   1 +
 tools/perf/util/record.h                |   3 +
 13 files changed, 865 insertions(+), 76 deletions(-)
 create mode 100644 tools/perf/arch/powerpc/util/htm.c
 create mode 100644 tools/perf/arch/powerpc/util/vpa-dtl.c
 create mode 100644 tools/perf/util/powerpc-htm.c
 create mode 100644 tools/perf/util/powerpc-htm.h

-- 
2.43.0