twister: qemu: fix mps2_an521 on Windows

tfm_integration samples fail on Windows on mps2_an521 platform,
because output from ninja process running QEMU freezes in re-build
phase.
Fix it by implementing named pipes to read output from QEMU process
directly using os.open and os.read methods.

Signed-off-by: Michal Smola <michal.smola@nxp.com>

scripts/pylib/twister/twisterlib/handlers.py

@@ -1050,14 +1050,12 @@ class QEMUHandler(Handler):
 
 
 class QEMUWinHandler(Handler):
-    """Spawns a thread to monitor QEMU output on Windows OS
+    """Spawns a thread to monitor QEMU output from pipes on Windows OS
 
-    We redirect subprocess output to pipe and monitor the pipes for output.
+     QEMU creates single duplex pipe at //.pipe/path, where path is fifo_fn.
      We need to do this as once qemu starts, it runs forever until killed.
      Test cases emit special messages to the console as they run, we check
      for these to collect whether the test passed or failed.
-    The pipe includes also messages from ninja command which is used for
-    running QEMU.
      """
 
     def __init__(self, instance, type_str):
@@ -1068,6 +1066,8 @@ class QEMUWinHandler(Handler):
 
         super().__init__(instance, type_str)
         self.pid_fn = os.path.join(instance.build_dir, "qemu.pid")
+        self.fifo_fn = os.path.join(instance.build_dir, "qemu-fifo")
+        self.pipe_handle = None
         self.pid = 0
         self.thread = None
         self.stop_thread = False
@@ -1109,6 +1109,8 @@ class QEMUWinHandler(Handler):
             except (ProcessLookupError, psutil.NoSuchProcess):
                 # Oh well, as long as it's dead! User probably sent Ctrl-C
                 pass
+            except OSError:
+                pass
 
     @staticmethod
     def _monitor_update_instance_info(handler, handler_time, out_state):
@@ -1165,15 +1167,21 @@ class QEMUWinHandler(Handler):
                     self.instance.reason = "Exited with {}".format(self.returncode)
             self.instance.add_missing_case_status("blocked")
 
-    def _enqueue_char(self, stdout, queue):
+    def _enqueue_char(self, queue):
         while not self.stop_thread:
+            if not self.pipe_handle:
                 try:
-                c = stdout.read(1)
-            except ValueError:
-                # Reading on closed file exception can occur when subprocess is killed.
-                # Can be ignored.
-                pass
-            else:
+                    self.pipe_handle = os.open(r"\\.\pipe\\" + self.fifo_fn, os.O_RDONLY)
+                except FileNotFoundError as e:
+                    if e.args[0] == 2:
+                        # Pipe is not opened yet, try again after a delay.
+                        time.sleep(1)
+                continue
+
+            c = ""
+            try:
+                c = os.read(self.pipe_handle, 1)
+            finally:
                 queue.put(c)
 
     def _monitor_output(self, queue, timeout, logfile, pid_fn, harness, ignore_unexpected_eof=False):
@@ -1283,10 +1291,11 @@ class QEMUWinHandler(Handler):
         self.stop_thread = False
         queue = Queue()
 
-        with subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE, cwd=self.build_dir) as proc:
+        with subprocess.Popen(command, stdout=subprocess.DEVNULL, stderr=subprocess.STDOUT,
+                              cwd=self.build_dir) as proc:
             logger.debug("Spawning QEMUHandler Thread for %s" % self.name)
 
-            self.thread = threading.Thread(target=self._enqueue_char, args=(proc.stdout, queue))
+            self.thread = threading.Thread(target=self._enqueue_char, args=(queue,))
             self.thread.daemon = True
             self.thread.start()
 
@@ -1312,6 +1321,12 @@ class QEMUWinHandler(Handler):
 
         logger.debug(f"return code from QEMU ({self.pid}): {self.returncode}")
 
+        os.close(self.pipe_handle)
+        self.pipe_handle = None
+
         self._update_instance_info(harness.state, is_timeout)
 
         self._final_handle_actions(harness, 0)
+
+    def get_fifo(self):
+        return self.fifo_fn

scripts/pylib/twister/twisterlib/testinstance.py

@@ -181,10 +181,9 @@ class TestInstance:
             if self.platform.simulation == "qemu":
                 if os.name != "nt":
                     handler = QEMUHandler(self, "qemu")
-                    handler.args.append(f"QEMU_PIPE={handler.get_fifo()}")
-                    handler.ready = True
                 else:
                     handler = QEMUWinHandler(self, "qemu")
+                handler.args.append(f"QEMU_PIPE={handler.get_fifo()}")
                 handler.ready = True
             else:
                 handler = SimulationHandler(self, self.platform.simulation)