[PATCH v4 41/49] perf test: Migrate Intel PT virtual LBR test to Python API

[Ian Rogers]

Migrate the Intel PT virtual LBR test from generating an inline legacy
perf script callback to using a standalone Python script
(perf_brstack_max.py) with the brstack iterator API in the perf Python
module.

Assisted-by: Antigravity:gemini-3.1-pro
Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
---
 .../perf/tests/shell/lib/perf_brstack_max.py  | 40 +++++++++++++++++
 tools/perf/tests/shell/test_intel_pt.sh       | 43 ++++++++-----------
 2 files changed, 58 insertions(+), 25 deletions(-)
 create mode 100644 tools/perf/tests/shell/lib/perf_brstack_max.py

diff --git a/tools/perf/tests/shell/lib/perf_brstack_max.py b/tools/perf/tests/shell/lib/perf_brstack_max.py
new file mode 100644
index 000000000000..cc065f07cfed
--- /dev/null
+++ b/tools/perf/tests/shell/lib/perf_brstack_max.py
@@ -0,0 +1,40 @@
+#!/usr/bin/python
+# SPDX-License-Identifier: GPL-2.0
+# Determine the maximum size of branch stacks in a perf.data file.
+
+import argparse
+import sys
+
+import perf
+
+def main():
+    ap = argparse.ArgumentParser()
+    ap.add_argument("-i", "--input", default="perf.data", help="Input file name")
+    args = ap.parse_args()
+
+    bmax = 0
+
+    def process_event(sample):
+        nonlocal bmax
+        try:
+            brstack = sample.brstack
+            if brstack:
+                n = len(list(brstack))
+                if n > bmax:
+                    bmax = n
+        except AttributeError:
+            pass
+
+    session = None
+    try:
+        session = perf.session(perf.data(args.input), sample=process_event)
+        session.process_events()
+        print("max brstack", bmax)
+    except Exception as e:
+        print(f"Error processing events: {e}", file=sys.stderr)
+        sys.exit(1)
+    finally:
+        session = None
+
+if __name__ == "__main__":
+    main()
diff --git a/tools/perf/tests/shell/test_intel_pt.sh b/tools/perf/tests/shell/test_intel_pt.sh
index a2e87ef09593..c0ecece0a825 100755
--- a/tools/perf/tests/shell/test_intel_pt.sh
+++ b/tools/perf/tests/shell/test_intel_pt.sh
@@ -1,6 +1,6 @@
 #!/bin/bash
-# Miscellaneous Intel PT testing (exclusive)
 # SPDX-License-Identifier: GPL-2.0
+# Miscellaneous Intel PT testing (exclusive)
 
 set -e
 
@@ -21,7 +21,6 @@ perfdatafile="${temp_dir}/test-perf.data"
 outfile="${temp_dir}/test-out.txt"
 errfile="${temp_dir}/test-err.txt"
 awkscript="${temp_dir}/awkscript"
-maxbrstack="${temp_dir}/maxbrstack.py"
 
 cleanup()
 {
@@ -375,34 +374,28 @@ test_kernel_trace()
 test_virtual_lbr()
 {
 	echo "--- Test virtual LBR ---"
-	# Check if python script is supported
-	libpython=$(perf version --build-options | grep python | grep -cv OFF)
-	if [ "${libpython}" != "1" ] ; then
-		echo "SKIP: python scripting is not supported"
+	# Run setup_python.sh in a subshell first so its 'exit 2' when Python is
+	# not detected skips only this subtest rather than exiting test_intel_pt.sh
+	# (which would trigger trap_cleanup and fail the suite).
+	# shellcheck source=lib/setup_python.sh
+	if ! ( . "${shelldir}"/lib/setup_python.sh ) ; then
 		return 2
 	fi
+	# shellcheck source=lib/setup_python.sh
+	. "${shelldir}"/lib/setup_python.sh
 
-	# Python script to determine the maximum size of branch stacks
-	cat << "_end_of_file_" > "${maxbrstack}"
-from __future__ import print_function
-
-bmax = 0
-
-def process_event(param_dict):
-	if "brstack" in param_dict:
-		brstack = param_dict["brstack"]
-		n = len(brstack)
-		global bmax
-		if n > bmax:
-			bmax = n
-
-def trace_end():
-	print("max brstack", bmax)
-_end_of_file_
+	if ! "$PYTHON" -c 'import perf' > /dev/null 2>&1; then
+		echo "SKIP: Python perf module not found"
+		return 2
+	fi
 
 	# Check if virtual lbr is working
-	perf_record_no_bpf -o "${perfdatafile}" --aux-sample -e '{intel_pt//,cycles}:u' uname
-	times_val=$(perf script -i "${perfdatafile}" --itrace=L -s "${maxbrstack}" 2>/dev/null | grep "max brstack " | cut -d " " -f 3)
+	perf_record_no_bpf -o "${tmpfile}" --aux-sample \
+		-e '{intel_pt//,cycles}:u' perf test -w brstack || return 1
+	perf inject --itrace=L -i "${tmpfile}" -o "${perfdatafile}" || return 1
+	output=$("$PYTHON" "${shelldir}/lib/perf_brstack_max.py" -i "${perfdatafile}") || return 1
+	echo "Debug: perf_brstack_max.py output: $output"
+	times_val=$(echo "$output" | grep "max brstack " | cut -d " " -f 3)
 	case "${times_val}" in
 		[0-9]*)	;;
 		*)	times_val=0;;
-- 
2.56.0.rc1.315.gc6ed9934b7-goog