fix(proton): Windows games see only the cores they are pinned to

Game cores pinned the game with taskset, but Wine counts the online
CPUs, so a game held to two cores still saw eight processors and sized
its thread pools for them. Prototype freezes at its splash screen that
way. When the session or a game profile limits the game cores, Wine now
gets WINE_CPU_TOPOLOGY for exactly those cores unless the profile sets
its own.

tools/linuxfs/overlay/usr/local/bin/droiddeck-game-env

@@ -351,6 +351,20 @@ def game_cores(env):
         print("droiddeck-game-env: could not use game cores %r (%s)" % (text, error), file=sys.stderr)
 
 
+def cpu_topology(env):
+    if env.get("WINE_CPU_TOPOLOGY") or not (env.get("DROIDDECK_GAME_CORES", "").strip() or env.get("BL_GAME_CPUS", "").strip()):
+        return
+    try:
+        cores = sorted(os.sched_getaffinity(0))
+    except OSError:
+        return
+    online = online_cores()
+    if not cores or set(cores) >= online or cores[-1] >= len(online):
+        return
+    env["WINE_CPU_TOPOLOGY"] = "%d:%s" % (len(cores), ",".join(map(str, cores)))
+    print("droiddeck-game-env: Windows sees %d cores (%s)" % (len(cores), env["WINE_CPU_TOPOLOGY"]), file=sys.stderr)
+
+
 def apply_config(env, config, app_id, fixes=None):
     if config.get("version") != 1:
         raise ValueError("unsupported environment configuration")
@@ -627,6 +641,7 @@ def main():
     env = vram_cap(env)
     env = force_ssbs(command, env)
     game_cores(env)
+    cpu_topology(env)
     try:
         xbox = runpy.run_path(str(Path(__file__).with_name("droiddeck-xbox")))
     except Exception as error:

tools/tests/test_game_environment.py

@@ -449,6 +449,23 @@ class GameEnvironmentTest(unittest.TestCase):
         self.assertEqual(calls, [{0, 1, 2}])
         self.assertEqual(MODULE["parse_cores"]("0,2-7"), {0, 2, 3, 4, 5, 6, 7})
 
+    def test_windows_games_see_only_the_cores_they_are_pinned_to(self):
+        os_mod = MODULE["os"]
+        online = {"online_cores": lambda: {0, 1, 2, 3, 4, 5, 6, 7}}
+        cases = [
+            ({"BL_GAME_CPUS": "6,7"}, {6, 7}, "2:6,7"),
+            ({"DROIDDECK_GAME_CORES": "0-2"}, {0, 1, 2}, "3:0,1,2"),
+            ({"BL_GAME_CPUS": "0-7"}, set(range(8)), None),
+            ({}, {6, 7}, None),
+            ({"BL_GAME_CPUS": "6,7", "WINE_CPU_TOPOLOGY": "4:0,1,2,3"}, {6, 7}, "4:0,1,2,3"),
+            ({"BL_GAME_CPUS": "9"}, {9}, None),
+        ]
+        for env, affinity, expected in cases:
+            with mock.patch.dict(MODULE["cpu_topology"].__globals__, online), \
+                    mock.patch.object(os_mod, "sched_getaffinity", return_value=affinity, create=True):
+                MODULE["cpu_topology"](env)
+            self.assertEqual(env.get("WINE_CPU_TOPOLOGY"), expected, env)
+
     def test_caravan_sandwitch_robocop_and_cyberpunk_run_at_feature_level_12_1(self):
         with tempfile.TemporaryDirectory() as tmp:
             caravan = Path(tmp) / "Caravan SandWitch"