Fix: honor disabled xdist in L2 dispatcher

conftest.py

@@ -1057,26 +1057,20 @@ def _on_done(res):
     # ----- Phase 2: L2 per-runtime subprocess -----
     l2_runtimes = _collect_st_runtimes(session.items, level=2)
     l2_failed = False
-    # When we have more than one device, enable pytest-xdist so the L2 phase
-    # spreads classes across devices. Each xdist worker slices --device 0-7
-    # down to one id in its own pytest_configure (above) and the st_worker
-    # fixture is session-scoped inside the worker — one ChipWorker per (runtime,
-    # device), reused across every class assigned to that worker.
-    xdist_available = False
-    if max_parallel > 1:
-        try:
-            import xdist  # noqa: F401,PLC0415
-
-            xdist_available = True
-        except ImportError:
-            print(
-                "\n[warning] -j > 1 but pytest-xdist not installed; "
-                "falling back to serial L2 phase. pip install pytest-xdist to enable.\n",
-                flush=True,
-            )
+    # An active pytest-xdist plugin spreads L2 classes across devices. Each
+    # worker slices --device 0-7 down to one id in pytest_configure (above),
+    # and the session-scoped st_worker fixture reuses one ChipWorker per
+    # (runtime, device).
+    xdist_active = max_parallel > 1 and cfg.pluginmanager.hasplugin("xdist")
+    if max_parallel > 1 and not xdist_active and not cfg.pluginmanager.is_blocked("xdist"):
+        print(
+            "\n[warning] --max-parallel > 1 but the pytest-xdist plugin is not active; "
+            "falling back to serial L2 phase. Install or enable pytest-xdist to use L2 parallelism.\n",
+            flush=True,
+        )
     for rt in l2_runtimes:
         cmd = base_args + ["--runtime", rt, "--level", "2"]
-        if xdist_available:
+        if xdist_active:
             cmd += ["-n", str(max_parallel), "--dist", "loadfile"]
         # Per-runtime sink for the in-process poison guards (issue #1110). Each
         # xdist worker appends the classes it poison-skips; we re-run them in a
@@ -1091,7 +1085,7 @@ def _on_done(res):
         # need to buffer their stdout — we can stream it directly through
         # the group markers. ``::group::`` on its own line before the run
         # opens the fold; ``::endgroup::`` after closes it.
-        label = f"L2 {rt}" + (f" [-n {max_parallel}]" if xdist_available else "")
+        label = f"L2 {rt}" + (f" [-n {max_parallel}]" if xdist_active else "")
         start = time.monotonic()
         print(f"::group::{label}", flush=True)
         result = subprocess.run(cmd, check=False, cwd=cwd, env=run_env)

docs/testing.md

@@ -852,6 +852,11 @@ pytest --runtime <rt> --level 2 --device 8-11 -n 4 --dist loadfile
 
 `pytest-xdist` starts 4 workers (`gw0`..`gw3`). Each worker's `pytest_configure` slices `--device 8-11` down to a single id (`gw0` → `8`, `gw1` → `9`, ...), and `st_worker` is session-scoped, so the worker initializes exactly one `ChipWorker(device=N)` and reuses it for every L2 class routed to it. `--dist loadfile` keeps all cases from one test file on the same worker, amortizing any file-level setup cost.
 
+An explicit `-p no:xdist` is authoritative for the L2 children inherited from
+the top-level invocation. The dispatcher omits `-n` and `--dist`, so each L2
+runtime subprocess executes serially. Resource-phase subprocess concurrency
+continues to follow `--max-parallel` because it does not use pytest-xdist.
+
 ### L2 phase — standalone fanout
 
 Standalone (`python test_*.py -d 8-11`) uses the same scheduler module: classes are round-robin assigned to `len(device_ids)` chunks, one subprocess per chunk launched with a single device and explicit `--case ClassName::` selectors.

tests/ut/py/test_l2_dispatch.py

@@ -0,0 +1,101 @@
+# Copyright (c) PyPTO Contributors.
+# This program is free software, you can redistribute it and/or modify it under the terms and conditions of
+# CANN Open Software License Agreement Version 2.0 (the "License").
+# Please refer to the License for details. You may not use this file except in compliance with the License.
+# THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND, EITHER EXPRESS OR IMPLIED,
+# INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT, MERCHANTABILITY, OR FITNESS FOR A PARTICULAR PURPOSE.
+# See LICENSE in the root of the software repository for the full text of the License.
+# -----------------------------------------------------------------------------------------------------------
+"""Tests for L2 dispatcher child-command construction."""
+
+from __future__ import annotations
+
+import importlib.util
+from pathlib import Path
+from types import SimpleNamespace
+
+_ROOT = Path(__file__).resolve().parents[3]
+
+
+def _load_root_conftest():
+    spec = importlib.util.spec_from_file_location("_root_conftest_l2_dispatch", _ROOT / "conftest.py")
+    assert spec is not None and spec.loader is not None
+    mod = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(mod)
+    return mod
+
+
+class _Config:
+    def __init__(self, *, xdist_active: bool, xdist_blocked: bool, disable_arg: bool = False):
+        args = ["first.py", "second.py"]
+        if disable_arg:
+            args.extend(["-p", "no:xdist"])
+        args.extend(["--max-parallel", "2"])
+        self.invocation_params = SimpleNamespace(
+            args=tuple(args),
+            dir=_ROOT,
+        )
+        self.pluginmanager = SimpleNamespace(
+            hasplugin=lambda name: name == "xdist" and xdist_active,
+            is_blocked=lambda name: name == "xdist" and xdist_blocked,
+        )
+
+    def getoption(self, name, default=None):
+        return {
+            "--device": "0-1",
+            "--exitfirst": False,
+            "--platform": "a2a3sim",
+            "--manual": "include",
+            "--max-parallel": "2",
+        }.get(name, default)
+
+
+def test_l2_dispatch_does_not_add_xdist_options_when_plugin_is_disabled(monkeypatch):
+    cf = _load_root_conftest()
+    commands = []
+
+    def fake_run(command, **_kwargs):
+        commands.append(command)
+        return SimpleNamespace(returncode=0)
+
+    monkeypatch.setattr(cf.subprocess, "run", fake_run)
+    config = _Config(xdist_active=False, xdist_blocked=True, disable_arg=True)
+    items = [
+        SimpleNamespace(cls=SimpleNamespace(_st_runtime="host_build_graph", _st_level=2)),
+        SimpleNamespace(cls=SimpleNamespace(_st_runtime="tensormap_and_ringbuffer", _st_level=2)),
+    ]
+    session = SimpleNamespace(config=config, items=items, testsfailed=0, testscollected=0)
+
+    assert cf._dispatch_test_phases(session, []) is True
+    assert len(commands) == 2
+    for command in commands:
+        assert "no:xdist" in command
+        assert "-n" not in command
+        assert "--dist" not in command
+
+
+def test_l2_dispatch_adds_xdist_options_when_plugin_is_active(monkeypatch):
+    cf = _load_root_conftest()
+    commands = []
+
+    def fake_run(command, **_kwargs):
+        commands.append(command)
+        return SimpleNamespace(returncode=0)
+
+    monkeypatch.setattr(cf.subprocess, "run", fake_run)
+    config = _Config(xdist_active=True, xdist_blocked=False)
+    items = [SimpleNamespace(cls=SimpleNamespace(_st_runtime="host_build_graph", _st_level=2))]
+    session = SimpleNamespace(config=config, items=items, testsfailed=0, testscollected=0)
+
+    assert cf._dispatch_test_phases(session, []) is True
+    assert len(commands) == 1
+    assert commands[0][-8:] == [
+        "--runtime",
+        "host_build_graph",
+        "--level",
+        "2",
+        "-n",
+        "2",
+        "--dist",
+        "loadfile",
+    ]