Merge remote-tracking branch 'remotes/jsnow-gitlab/tags/python-pull-request' into staging

Pull request

# gpg: Signature made Tue 20 Oct 2020 20:04:54 BST
# gpg:                using RSA key F9B7ABDBBCACDF95BE76CBD07DEF8106AAFC390E
# gpg: Good signature from "John Snow (John Huston) <jsnow@redhat.com>" [full]
# Primary key fingerprint: FAEB 9711 A12C F475 812F  18F2 88A9 064D 1835 61EB
#      Subkey fingerprint: F9B7 ABDB BCAC DF95 BE76  CBD0 7DEF 8106 AAFC 390E

* remotes/jsnow-gitlab/tags/python-pull-request: (21 commits)
  python/qemu/qmp.py: Fix settimeout operation
  python/qemu/qmp.py: re-raise OSError when encountered
  python: add mypy config
  python/qemu/qmp.py: Preserve error context on re-raise
  python/qemu/console_socket.py: avoid encoding to/from string
  python/qemu/console_socket.py: Add type hint annotations
  python/qemu/console_socket.py: Clarify type of drain_thread
  python/qemu/console_socket.py: fix typing of settimeout
  python/qemu/console_socket.py: Correct type of recv()
  python/qemu: Add mypy type annotations
  iotests.py: Adjust HMP kwargs typing
  python/qemu: make 'args' style arguments immutable
  python/machine.py: fix _popen access
  python/machine.py: Add _qmp access shim
  python/machine.py: use qmp.command
  python/machine.py: Handle None events in events_wait
  python/machine.py: Don't modify state in _base_args()
  python/machine.py: reorder __init__
  python/machine.py: Fix monitor address typing
  python/qemu: use isort to lay out imports
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

9 files changed, 326 insertions, 211 deletions

diff --git a/MAINTAINERS b/MAINTAINERS
index a7f0acf..6a197bd 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2373,11 +2373,18 @@ S: Maintained
 F: include/sysemu/cryptodev*.h
 F: backends/cryptodev*.c
 
+Python library
+M: John Snow <jsnow@redhat.com>
+M: Cleber Rosa <crosa@redhat.com>
+R: Eduardo Habkost <ehabkost@redhat.com>
+S: Maintained
+F: python/
+T: git https://gitlab.com/jsnow/qemu.git python
+
 Python scripts
 M: Eduardo Habkost <ehabkost@redhat.com>
 M: Cleber Rosa <crosa@redhat.com>
 S: Odd fixes
-F: python/qemu/*py
 F: scripts/*.py
 F: tests/*.py
 
diff --git a/python/mypy.ini b/python/mypy.ini
new file mode 100644
index 0000000..1a581c5
--- /dev/null
+++ b/python/mypy.ini
@@ -0,0 +1,4 @@
+[mypy]
+strict = True
+python_version = 3.6
+warn_unused_configs = True
diff --git a/python/qemu/.isort.cfg b/python/qemu/.isort.cfg
new file mode 100644
index 0000000..6d0fd6c
--- /dev/null
+++ b/python/qemu/.isort.cfg
@@ -0,0 +1,7 @@
+[settings]
+force_grid_wrap=4
+force_sort_within_sections=True
+include_trailing_comma=True
+line_length=72
+lines_after_imports=2
+multi_line_output=3
\ No newline at end of file
diff --git a/python/qemu/accel.py b/python/qemu/accel.py
index 7fabe62..297933d 100644
--- a/python/qemu/accel.py
+++ b/python/qemu/accel.py
@@ -17,6 +17,8 @@ accelerators.
 import logging
 import os
 import subprocess
+from typing import List, Optional
+
 
 LOG = logging.getLogger(__name__)
 
@@ -29,7 +31,7 @@ ADDITIONAL_ARCHES = {
 }
 
 
-def list_accel(qemu_bin):
+def list_accel(qemu_bin: str) -> List[str]:
     """
     List accelerators enabled in the QEMU binary.
 
@@ -49,7 +51,8 @@ def list_accel(qemu_bin):
     return [acc.strip() for acc in out.splitlines()[1:]]
 
 
-def kvm_available(target_arch=None, qemu_bin=None):
+def kvm_available(target_arch: Optional[str] = None,
+                  qemu_bin: Optional[str] = None) -> bool:
     """
     Check if KVM is available using the following heuristic:
       - Kernel module is present in the host;
@@ -72,7 +75,7 @@ def kvm_available(target_arch=None, qemu_bin=None):
     return True
 
 
-def tcg_available(qemu_bin):
+def tcg_available(qemu_bin: str) -> bool:
     """
     Check if TCG is available.
 
diff --git a/python/qemu/console_socket.py b/python/qemu/console_socket.py
index 70869fb..f060d79 100644
--- a/python/qemu/console_socket.py
+++ b/python/qemu/console_socket.py
@@ -13,10 +13,11 @@ which can drain a socket and optionally dump the bytes to file.
 # the COPYING file in the top-level directory.
 #
 
+from collections import deque
 import socket
 import threading
-from collections import deque
 import time
+from typing import Deque, Optional
 
 
 class ConsoleSocket(socket.socket):
@@ -29,22 +30,22 @@ class ConsoleSocket(socket.socket):
     Optionally a file path can be passed in and we will also
     dump the characters to this file for debugging purposes.
     """
-    def __init__(self, address, file=None, drain=False):
-        self._recv_timeout_sec = 300
+    def __init__(self, address: str, file: Optional[str] = None,
+                 drain: bool = False):
+        self._recv_timeout_sec = 300.0
         self._sleep_time = 0.5
-        self._buffer = deque()
+        self._buffer: Deque[int] = deque()
         socket.socket.__init__(self, socket.AF_UNIX, socket.SOCK_STREAM)
         self.connect(address)
         self._logfile = None
         if file:
-            self._logfile = open(file, "w")
+            self._logfile = open(file, "bw")
         self._open = True
+        self._drain_thread = None
         if drain:
             self._drain_thread = self._thread_start()
-        else:
-            self._drain_thread = None
 
-    def _drain_fn(self):
+    def _drain_fn(self) -> None:
         """Drains the socket and runs while the socket is open."""
         while self._open:
             try:
@@ -55,7 +56,7 @@ class ConsoleSocket(socket.socket):
                 # self._open is set to False.
                 time.sleep(self._sleep_time)
 
-    def _thread_start(self):
+    def _thread_start(self) -> threading.Thread:
         """Kick off a thread to drain the socket."""
         # Configure socket to not block and timeout.
         # This allows our drain thread to not block
@@ -67,7 +68,7 @@ class ConsoleSocket(socket.socket):
         drain_thread.start()
         return drain_thread
 
-    def close(self):
+    def close(self) -> None:
         """Close the base object and wait for the thread to terminate"""
         if self._open:
             self._open = False
@@ -79,51 +80,42 @@ class ConsoleSocket(socket.socket):
                 self._logfile.close()
                 self._logfile = None
 
-    def _drain_socket(self):
+    def _drain_socket(self) -> None:
         """process arriving characters into in memory _buffer"""
         data = socket.socket.recv(self, 1)
-        # latin1 is needed since there are some chars
-        # we are receiving that cannot be encoded to utf-8
-        # such as 0xe2, 0x80, 0xA6.
-        string = data.decode("latin1")
         if self._logfile:
-            self._logfile.write("{}".format(string))
+            self._logfile.write(data)
             self._logfile.flush()
-        for c in string:
-            self._buffer.extend(c)
+        self._buffer.extend(data)
 
-    def recv(self, bufsize=1):
+    def recv(self, bufsize: int = 1, flags: int = 0) -> bytes:
         """Return chars from in memory buffer.
            Maintains the same API as socket.socket.recv.
         """
         if self._drain_thread is None:
             # Not buffering the socket, pass thru to socket.
-            return socket.socket.recv(self, bufsize)
+            return socket.socket.recv(self, bufsize, flags)
+        assert not flags, "Cannot pass flags to recv() in drained mode"
         start_time = time.time()
         while len(self._buffer) < bufsize:
             time.sleep(self._sleep_time)
             elapsed_sec = time.time() - start_time
             if elapsed_sec > self._recv_timeout_sec:
                 raise socket.timeout
-        chars = ''.join([self._buffer.popleft() for i in range(bufsize)])
-        # We choose to use latin1 to remain consistent with
-        # handle_read() and give back the same data as the user would
-        # receive if they were reading directly from the
-        # socket w/o our intervention.
-        return chars.encode("latin1")
+        return bytes((self._buffer.popleft() for i in range(bufsize)))
 
-    def setblocking(self, value):
+    def setblocking(self, value: bool) -> None:
         """When not draining we pass thru to the socket,
            since when draining we control socket blocking.
         """
         if self._drain_thread is None:
             socket.socket.setblocking(self, value)
 
-    def settimeout(self, seconds):
+    def settimeout(self, value: Optional[float]) -> None:
         """When not draining we pass thru to the socket,
            since when draining we control the timeout.
         """
-        if seconds is not None:
-            self._recv_timeout_sec = seconds
+        if value is not None:
+            self._recv_timeout_sec = value
         if self._drain_thread is None:
-            socket.socket.settimeout(self, seconds)
+            socket.socket.settimeout(self, value)
diff --git a/python/qemu/machine.py b/python/qemu/machine.py
index 82f3731..6420f01 100644
--- a/python/qemu/machine.py
+++ b/python/qemu/machine.py
@@ -18,17 +18,29 @@ which provides facilities for managing the lifetime of a QEMU VM.
 #
 
 import errno
+from itertools import chain
 import logging
 import os
-import subprocess
 import shutil
 import signal
+import socket
+import subprocess
 import tempfile
-from typing import Optional, Type
 from types import TracebackType
-from . import console_socket
+from typing import (
+    Any,
+    BinaryIO,
+    Dict,
+    List,
+    Optional,
+    Sequence,
+    Tuple,
+    Type,
+)
+
+from . import console_socket, qmp
+from .qmp import QMPMessage, QMPReturnValue, SocketAddrT
 
-from . import qmp
 
 LOG = logging.getLogger(__name__)
 
@@ -57,7 +69,7 @@ class AbnormalShutdown(QEMUMachineError):
 
 class QEMUMachine:
     """
-    A QEMU VM
+    A QEMU VM.
 
     Use this object as a context manager to ensure
     the QEMU process terminates::
@@ -67,10 +79,17 @@ class QEMUMachine:
         # vm is guaranteed to be shut down here
     """
 
-    def __init__(self, binary, args=None, wrapper=None, name=None,
-                 test_dir="/var/tmp", monitor_address=None,
-                 socket_scm_helper=None, sock_dir=None,
-                 drain_console=False, console_log=None):
+    def __init__(self,
+                 binary: str,
+                 args: Sequence[str] = (),
+                 wrapper: Sequence[str] = (),
+                 name: Optional[str] = None,
+                 test_dir: str = "/var/tmp",
+                 monitor_address: Optional[SocketAddrT] = None,
+                 socket_scm_helper: Optional[str] = None,
+                 sock_dir: Optional[str] = None,
+                 drain_console: bool = False,
+                 console_log: Optional[str] = None):
         '''
         Initialize a QEMUMachine
 
@@ -82,45 +101,30 @@ class QEMUMachine:
         @param monitor_address: address for QMP monitor
         @param socket_scm_helper: helper program, required for send_fd_scm()
         @param sock_dir: where to create socket (overrides test_dir for sock)
-        @param console_log: (optional) path to console log file
         @param drain_console: (optional) True to drain console socket to buffer
+        @param console_log: (optional) path to console log file
         @note: Qemu process is not started until launch() is used.
         '''
-        if args is None:
-            args = []
-        if wrapper is None:
-            wrapper = []
-        if name is None:
-            name = "qemu-%d" % os.getpid()
-        if sock_dir is None:
-            sock_dir = test_dir
-        self._name = name
-        self._monitor_address = monitor_address
-        self._vm_monitor = None
-        self._qemu_log_path = None
-        self._qemu_log_file = None
-        self._popen = None
+        # Direct user configuration
+
         self._binary = binary
-        self._args = list(args)     # Force copy args in case we modify them
+        self._args = list(args)
         self._wrapper = wrapper
-        self._events = []
-        self._iolog = None
-        self._socket_scm_helper = socket_scm_helper
-        self._qmp_set = True   # Enable QMP monitor by default.
-        self._qmp = None
-        self._qemu_full_args = None
+
+        self._name = name or "qemu-%d" % os.getpid()
         self._test_dir = test_dir
-        self._temp_dir = None
-        self._sock_dir = sock_dir
-        self._launched = False
-        self._machine = None
-        self._console_index = 0
-        self._console_set = False
-        self._console_device_type = None
-        self._console_address = None
-        self._console_socket = None
-        self._remove_files = []
-        self._user_killed = False
+        self._sock_dir = sock_dir or self._test_dir
+        self._socket_scm_helper = socket_scm_helper
+
+        if monitor_address is not None:
+            self._monitor_address = monitor_address
+            self._remove_monitor_sockfile = False
+        else:
+            self._monitor_address = os.path.join(
+                self._sock_dir, f"{self._name}-monitor.sock"
+            )
+            self._remove_monitor_sockfile = True
+
         self._console_log_path = console_log
         if self._console_log_path:
             # In order to log the console, buffering needs to be enabled.
@@ -128,7 +132,29 @@ class QEMUMachine:
         else:
             self._drain_console = drain_console
 
-    def __enter__(self):
+        # Runstate
+        self._qemu_log_path: Optional[str] = None
+        self._qemu_log_file: Optional[BinaryIO] = None
+        self._popen: Optional['subprocess.Popen[bytes]'] = None
+        self._events: List[QMPMessage] = []
+        self._iolog: Optional[str] = None
+        self._qmp_set = True   # Enable QMP monitor by default.
+        self._qmp_connection: Optional[qmp.QEMUMonitorProtocol] = None
+        self._qemu_full_args: Tuple[str, ...] = ()
+        self._temp_dir: Optional[str] = None
+        self._launched = False
+        self._machine: Optional[str] = None
+        self._console_index = 0
+        self._console_set = False
+        self._console_device_type: Optional[str] = None
+        self._console_address = os.path.join(
+            self._sock_dir, f"{self._name}-console.sock"
+        )
+        self._console_socket: Optional[socket.socket] = None
+        self._remove_files: List[str] = []
+        self._user_killed = False
+
+    def __enter__(self) -> 'QEMUMachine':
         return self
 
     def __exit__(self,
@@ -137,14 +163,15 @@ class QEMUMachine:
                  exc_tb: Optional[TracebackType]) -> None:
         self.shutdown()
 
-    def add_monitor_null(self):
+    def add_monitor_null(self) -> None:
         """
         This can be used to add an unused monitor instance.
         """
         self._args.append('-monitor')
         self._args.append('null')
 
-    def add_fd(self, fd, fdset, opaque, opts=''):
+    def add_fd(self, fd: int, fdset: int,
+               opaque: str, opts: str = '') -> 'QEMUMachine':
         """
         Pass a file descriptor to the VM
         """
@@ -163,7 +190,8 @@ class QEMUMachine:
         self._args.append(','.join(options))
         return self
 
-    def send_fd_scm(self, fd=None, file_path=None):
+    def send_fd_scm(self, fd: Optional[int] = None,
+                    file_path: Optional[str] = None) -> int:
         """
         Send an fd or file_path to socket_scm_helper.
 
@@ -207,7 +235,7 @@ class QEMUMachine:
         return proc.returncode
 
     @staticmethod
-    def _remove_if_exists(path):
+    def _remove_if_exists(path: str) -> None:
         """
         Remove file object at path if it exists
         """
@@ -218,46 +246,52 @@ class QEMUMachine:
                 return
             raise
 
-    def is_running(self):
+    def is_running(self) -> bool:
         """Returns true if the VM is running."""
         return self._popen is not None and self._popen.poll() is None
 
-    def exitcode(self):
+    @property
+    def _subp(self) -> 'subprocess.Popen[bytes]':
+        if self._popen is None:
+            raise QEMUMachineError('Subprocess pipe not present')
+        return self._popen
+
+    def exitcode(self) -> Optional[int]:
         """Returns the exit code if possible, or None."""
         if self._popen is None:
             return None
         return self._popen.poll()
 
-    def get_pid(self):
+    def get_pid(self) -> Optional[int]:
         """Returns the PID of the running process, or None."""
         if not self.is_running():
             return None
-        return self._popen.pid
+        return self._subp.pid
 
-    def _load_io_log(self):
+    def _load_io_log(self) -> None:
         if self._qemu_log_path is not None:
             with open(self._qemu_log_path, "r") as iolog:
                 self._iolog = iolog.read()
 
-    def _base_args(self):
+    @property
+    def _base_args(self) -> List[str]:
         args = ['-display', 'none', '-vga', 'none']
+
         if self._qmp_set:
             if isinstance(self._monitor_address, tuple):
-                moncdev = "socket,id=mon,host=%s,port=%s" % (
-                    self._monitor_address[0],
-                    self._monitor_address[1])
+                moncdev = "socket,id=mon,host={},port={}".format(
+                    *self._monitor_address
+                )
             else:
-                moncdev = 'socket,id=mon,path=%s' % self._vm_monitor
+                moncdev = f"socket,id=mon,path={self._monitor_address}"
             args.extend(['-chardev', moncdev, '-mon',
                          'chardev=mon,mode=control'])
+
         if self._machine is not None:
             args.extend(['-machine', self._machine])
         for _ in range(self._console_index):
             args.extend(['-serial', 'null'])
         if self._console_set:
-            self._console_address = os.path.join(self._sock_dir,
-                                                 self._name + "-console.sock")
-            self._remove_files.append(self._console_address)
             chardev = ('socket,id=console,path=%s,server,nowait' %
                        self._console_address)
             args.extend(['-chardev', chardev])
@@ -268,26 +302,29 @@ class QEMUMachine:
                 args.extend(['-device', device])
         return args
 
-    def _pre_launch(self):
+    def _pre_launch(self) -> None:
         self._temp_dir = tempfile.mkdtemp(dir=self._test_dir)
         self._qemu_log_path = os.path.join(self._temp_dir, self._name + ".log")
         self._qemu_log_file = open(self._qemu_log_path, 'wb')
 
+        if self._console_set:
+            self._remove_files.append(self._console_address)
+
         if self._qmp_set:
-            if self._monitor_address is not None:
-                self._vm_monitor = self._monitor_address
-            else:
-                self._vm_monitor = os.path.join(self._sock_dir,
-                                                self._name + "-monitor.sock")
-                self._remove_files.append(self._vm_monitor)
-            self._qmp = qmp.QEMUMonitorProtocol(self._vm_monitor, server=True,
-                                                nickname=self._name)
-
-    def _post_launch(self):
-        if self._qmp:
+            if self._remove_monitor_sockfile:
+                assert isinstance(self._monitor_address, str)
+                self._remove_files.append(self._monitor_address)
+            self._qmp_connection = qmp.QEMUMonitorProtocol(
+                self._monitor_address,
+                server=True,
+                nickname=self._name
+            )
+
+    def _post_launch(self) -> None:
+        if self._qmp_connection:
             self._qmp.accept()
 
-    def _post_shutdown(self):
+    def _post_shutdown(self) -> None:
         """
         Called to cleanup the VM instance after the process has exited.
         May also be called after a failed launch.
@@ -295,9 +332,9 @@ class QEMUMachine:
         # Comprehensive reset for the failed launch case:
         self._early_cleanup()
 
-        if self._qmp:
+        if self._qmp_connection:
             self._qmp.close()
-            self._qmp = None
+            self._qmp_connection = None
 
         self._load_io_log()
 
@@ -327,7 +364,7 @@ class QEMUMachine:
         self._user_killed = False
         self._launched = False
 
-    def launch(self):
+    def launch(self) -> None:
         """
         Launch the VM and make sure we cleanup and expose the
         command line/output in case of exception
@@ -337,7 +374,7 @@ class QEMUMachine:
             raise QEMUMachineError('VM already launched')
 
         self._iolog = None
-        self._qemu_full_args = None
+        self._qemu_full_args = ()
         try:
             self._launch()
             self._launched = True
@@ -351,14 +388,18 @@ class QEMUMachine:
                 LOG.debug('Output: %r', self._iolog)
             raise
 
-    def _launch(self):
+    def _launch(self) -> None:
         """
         Launch the VM and establish a QMP connection
         """
         devnull = open(os.path.devnull, 'rb')
         self._pre_launch()
-        self._qemu_full_args = (self._wrapper + [self._binary] +
-                                self._base_args() + self._args)
+        self._qemu_full_args = tuple(
+            chain(self._wrapper,
+                  [self._binary],
+                  self._base_args,
+                  self._args)
+        )
         LOG.debug('VM launch command: %r', ' '.join(self._qemu_full_args))
         self._popen = subprocess.Popen(self._qemu_full_args,
                                        stdin=devnull,
@@ -390,8 +431,8 @@ class QEMUMachine:
             waiting for the QEMU process to terminate.
         """
         self._early_cleanup()
-        self._popen.kill()
-        self._popen.wait(timeout=60)
+        self._subp.kill()
+        self._subp.wait(timeout=60)
 
     def _soft_shutdown(self, timeout: Optional[int],
                        has_quit: bool = False) -> None:
@@ -409,13 +450,13 @@ class QEMUMachine:
         """
         self._early_cleanup()
 
-        if self._qmp is not None:
+        if self._qmp_connection:
             if not has_quit:
                 # Might raise ConnectionReset
                 self._qmp.cmd('quit')
 
         # May raise subprocess.TimeoutExpired
-        self._popen.wait(timeout=timeout)
+        self._subp.wait(timeout=timeout)
 
     def _do_shutdown(self, timeout: Optional[int],
                      has_quit: bool = False) -> None:
@@ -466,7 +507,7 @@ class QEMUMachine:
         finally:
             self._post_shutdown()
 
-    def kill(self):
+    def kill(self) -> None:
         """
         Terminate the VM forcefully, wait for it to exit, and perform cleanup.
         """
@@ -481,7 +522,7 @@ class QEMUMachine:
         """
         self.shutdown(has_quit=True, timeout=timeout)
 
-    def set_qmp_monitor(self, enabled=True):
+    def set_qmp_monitor(self, enabled: bool = True) -> None:
         """
         Set the QMP monitor.
 
@@ -490,39 +531,45 @@ class QEMUMachine:
                         line. Default is True.
         @note: call this function before launch().
         """
-        if enabled:
-            self._qmp_set = True
-        else:
-            self._qmp_set = False
-            self._qmp = None
+        self._qmp_set = enabled
 
-    def qmp(self, cmd, conv_keys=True, **args):
-        """
-        Invoke a QMP command and return the response dict
-        """
+    @property
+    def _qmp(self) -> qmp.QEMUMonitorProtocol:
+        if self._qmp_connection is None:
+            raise QEMUMachineError("Attempt to access QMP with no connection")
+        return self._qmp_connection
+
+    @classmethod
+    def _qmp_args(cls, _conv_keys: bool = True, **args: Any) -> Dict[str, Any]:
         qmp_args = dict()
         for key, value in args.items():
-            if conv_keys:
+            if _conv_keys:
                 qmp_args[key.replace('_', '-')] = value
             else:
                 qmp_args[key] = value
+        return qmp_args
 
+    def qmp(self, cmd: str,
+            conv_keys: bool = True,
+            **args: Any) -> QMPMessage:
+        """
+        Invoke a QMP command and return the response dict
+        """
+        qmp_args = self._qmp_args(conv_keys, **args)
         return self._qmp.cmd(cmd, args=qmp_args)
 
-    def command(self, cmd, conv_keys=True, **args):
+    def command(self, cmd: str,
+                conv_keys: bool = True,
+                **args: Any) -> QMPReturnValue:
         """
         Invoke a QMP command.
         On success return the response dict.
         On failure raise an exception.
         """
-        reply = self.qmp(cmd, conv_keys, **args)
-        if reply is None:
-            raise qmp.QMPError("Monitor is closed")
-        if "error" in reply:
-            raise qmp.QMPResponseError(reply)
-        return reply["return"]
+        qmp_args = self._qmp_args(conv_keys, **args)
+        return self._qmp.command(cmd, **qmp_args)
 
-    def get_qmp_event(self, wait=False):
+    def get_qmp_event(self, wait: bool = False) -> Optional[QMPMessage]:
         """
         Poll for one queued QMP events and return it
         """
@@ -530,7 +577,7 @@ class QEMUMachine:
             return self._events.pop(0)
         return self._qmp.pull_event(wait=wait)
 
-    def get_qmp_events(self, wait=False):
+    def get_qmp_events(self, wait: bool = False) -> List[QMPMessage]:
         """
         Poll for queued QMP events and return a list of dicts
         """
@@ -541,7 +588,7 @@ class QEMUMachine:
         return events
 
     @staticmethod
-    def event_match(event, match=None):
+    def event_match(event: Any, match: Optional[Any]) -> bool:
         """
         Check if an event matches optional match criteria.
 
@@ -571,9 +618,11 @@ class QEMUMachine:
             return True
         except TypeError:
             # either match or event wasn't iterable (not a dict)
-            return match == event
+            return bool(match == event)
 
-    def event_wait(self, name, timeout=60.0, match=None):
+    def event_wait(self, name: str,
+                   timeout: float = 60.0,
+                   match: Optional[QMPMessage] = None) -> Optional[QMPMessage]:
         """
         event_wait waits for and returns a named event from QMP with a timeout.
 
@@ -583,22 +632,33 @@ class QEMUMachine:
         """
         return self.events_wait([(name, match)], timeout)
 
-    def events_wait(self, events, timeout=60.0):
+    def events_wait(self,
+                    events: Sequence[Tuple[str, Any]],
+                    timeout: float = 60.0) -> Optional[QMPMessage]:
         """
-        events_wait waits for and returns a named event
-        from QMP with a timeout.
+        events_wait waits for and returns a single named event from QMP.
+        In the case of multiple qualifying events, this function returns the
+        first one.
 
-        events: a sequence of (name, match_criteria) tuples.
-                The match criteria are optional and may be None.
-                See event_match for details.
-        timeout: QEMUMonitorProtocol.pull_event timeout parameter.
+        :param events: A sequence of (name, match_criteria) tuples.
+                       The match criteria are optional and may be None.
+                       See event_match for details.
+        :param timeout: Optional timeout, in seconds.
+                        See QEMUMonitorProtocol.pull_event.
+
+        :raise QMPTimeoutError: If timeout was non-zero and no matching events
+                                were found.
+        :return: A QMP event matching the filter criteria.
+                 If timeout was 0 and no event matched, None.
         """
-        def _match(event):
+        def _match(event: QMPMessage) -> bool:
             for name, match in events:
                 if event['event'] == name and self.event_match(event, match):
                     return True
             return False
 
+        event: Optional[QMPMessage]
+
         # Search cached events
         for event in self._events:
             if _match(event):
@@ -608,26 +668,30 @@ class QEMUMachine:
         # Poll for new events
         while True:
             event = self._qmp.pull_event(wait=timeout)
+            if event is None:
+                # NB: None is only returned when timeout is false-ish.
+                # Timeouts raise QMPTimeoutError instead!
+                break
             if _match(event):
                 return event
             self._events.append(event)
 
         return None
 
-    def get_log(self):
+    def get_log(self) -> Optional[str]:
         """
         After self.shutdown or failed qemu execution, this returns the output
         of the qemu process.
         """
         return self._iolog
 
-    def add_args(self, *args):
+    def add_args(self, *args: str) -> None:
         """
         Adds to the list of extra arguments to be given to the QEMU binary
         """
         self._args.extend(args)
 
-    def set_machine(self, machine_type):
+    def set_machine(self, machine_type: str) -> None:
         """
         Sets the machine type
 
@@ -636,7 +700,9 @@ class QEMUMachine:
         """
         self._machine = machine_type
 
-    def set_console(self, device_type=None, console_index=0):
+    def set_console(self,
+                    device_type: Optional[str] = None,
+                    console_index: int = 0) -> None:
         """
         Sets the device type for a console device
 
@@ -667,7 +733,7 @@ class QEMUMachine:
         self._console_index = console_index
 
     @property
-    def console_socket(self):
+    def console_socket(self) -> socket.socket:
         """
         Returns a socket connected to the console
         """
diff --git a/python/qemu/qmp.py b/python/qemu/qmp.py
index 7935dab..2cd4d43 100644
--- a/python/qemu/qmp.py
+++ b/python/qemu/qmp.py
@@ -7,21 +7,22 @@
 # This work is licensed under the terms of the GNU GPL, version 2.  See
 # the COPYING file in the top-level directory.
 
-import json
 import errno
-import socket
+import json
 import logging
+import socket
+from types import TracebackType
 from typing import (
     Any,
-    cast,
     Dict,
+    List,
     Optional,
     TextIO,
-    Type,
     Tuple,
+    Type,
     Union,
+    cast,
 )
-from types import TracebackType
 
 
 # QMPMessage is a QMP Message of any kind.
@@ -90,7 +91,9 @@ class QEMUMonitorProtocol:
     #: Logger object for debugging messages
     logger = logging.getLogger('QMP')
 
-    def __init__(self, address, server=False, nickname=None):
+    def __init__(self, address: SocketAddrT,
+                 server: bool = False,
+                 nickname: Optional[str] = None):
         """
         Create a QEMUMonitorProtocol class.
 
@@ -102,7 +105,7 @@ class QEMUMonitorProtocol:
         @note No connection is established, this is done by the connect() or
               accept() methods
         """
-        self.__events = []
+        self.__events: List[QMPMessage] = []
         self.__address = address
         self.__sock = self.__get_sock()
         self.__sockfile: Optional[TextIO] = None
@@ -114,14 +117,14 @@ class QEMUMonitorProtocol:
             self.__sock.bind(self.__address)
             self.__sock.listen(1)
 
-    def __get_sock(self):
+    def __get_sock(self) -> socket.socket:
         if isinstance(self.__address, tuple):
             family = socket.AF_INET
         else:
             family = socket.AF_UNIX
         return socket.socket(family, socket.SOCK_STREAM)
 
-    def __negotiate_capabilities(self):
+    def __negotiate_capabilities(self) -> QMPMessage:
         greeting = self.__json_read()
         if greeting is None or "QMP" not in greeting:
             raise QMPConnectError
@@ -131,7 +134,7 @@ class QEMUMonitorProtocol:
             return greeting
         raise QMPCapabilitiesError
 
-    def __json_read(self, only_event=False):
+    def __json_read(self, only_event: bool = False) -> Optional[QMPMessage]:
         assert self.__sockfile is not None
         while True:
             data = self.__sockfile.readline()
@@ -148,7 +151,7 @@ class QEMUMonitorProtocol:
                     continue
             return resp
 
-    def __get_events(self, wait=False):
+    def __get_events(self, wait: Union[bool, float] = False) -> None:
         """
         Check for new events in the stream and cache them in __events.
 
@@ -161,15 +164,19 @@ class QEMUMonitorProtocol:
                                 retrieved or if some other error occurred.
         """
 
+        # Current timeout and blocking status
+        current_timeout = self.__sock.gettimeout()
+
         # Check for new events regardless and pull them into the cache:
-        self.__sock.setblocking(False)
+        self.__sock.settimeout(0)  # i.e. setblocking(False)
         try:
             self.__json_read()
         except OSError as err:
-            if err.errno == errno.EAGAIN:
-                # No data available
-                pass
-        self.__sock.setblocking(True)
+            # EAGAIN: No data available; not critical
+            if err.errno != errno.EAGAIN:
+                raise
+        finally:
+            self.__sock.settimeout(current_timeout)
 
         # Wait for new events, if needed.
         # if wait is 0.0, this means "no wait" and is also implicitly false.
@@ -178,15 +185,18 @@ class QEMUMonitorProtocol:
                 self.__sock.settimeout(wait)
             try:
                 ret = self.__json_read(only_event=True)
-            except socket.timeout:
-                raise QMPTimeoutError("Timeout waiting for event")
-            except:
-                raise QMPConnectError("Error while reading from socket")
+            except socket.timeout as err:
+                raise QMPTimeoutError("Timeout waiting for event") from err
+            except Exception as err:
+                msg = "Error while reading from socket"
+                raise QMPConnectError(msg) from err
+            finally:
+                self.__sock.settimeout(current_timeout)
+
             if ret is None:
                 raise QMPConnectError("Error while reading from socket")
-            self.__sock.settimeout(None)
 
-    def __enter__(self):
+    def __enter__(self) -> 'QEMUMonitorProtocol':
         # Implement context manager enter function.
         return self
 
@@ -199,7 +209,7 @@ class QEMUMonitorProtocol:
         # Implement context manager exit function.
         self.close()
 
-    def connect(self, negotiate=True):
+    def connect(self, negotiate: bool = True) -> Optional[QMPMessage]:
         """
         Connect to the QMP Monitor and perform capabilities negotiation.
 
@@ -214,7 +224,7 @@ class QEMUMonitorProtocol:
             return self.__negotiate_capabilities()
         return None
 
-    def accept(self, timeout=15.0):
+    def accept(self, timeout: Optional[float] = 15.0) -> QMPMessage:
         """
         Await connection from QMP Monitor and perform capabilities negotiation.
 
@@ -250,7 +260,9 @@ class QEMUMonitorProtocol:
         self.logger.debug("<<< %s", resp)
         return resp
 
-    def cmd(self, name, args=None, cmd_id=None):
+    def cmd(self, name: str,
+            args: Optional[Dict[str, Any]] = None,
+            cmd_id: Optional[Any] = None) -> QMPMessage:
         """
         Build a QMP command and send it to the QMP Monitor.
 
@@ -258,14 +270,14 @@ class QEMUMonitorProtocol:
         @param args: command arguments (dict)
         @param cmd_id: command id (dict, list, string or int)
         """
-        qmp_cmd = {'execute': name}
+        qmp_cmd: QMPMessage = {'execute': name}
         if args:
             qmp_cmd['arguments'] = args
         if cmd_id:
             qmp_cmd['id'] = cmd_id
         return self.cmd_obj(qmp_cmd)
 
-    def command(self, cmd, **kwds):
+    def command(self, cmd: str, **kwds: Any) -> QMPReturnValue:
         """
         Build and send a QMP command to the monitor, report errors if any
         """
@@ -278,7 +290,8 @@ class QEMUMonitorProtocol:
             )
         return cast(QMPReturnValue, ret['return'])
 
-    def pull_event(self, wait=False):
+    def pull_event(self,
+                   wait: Union[bool, float] = False) -> Optional[QMPMessage]:
         """
         Pulls a single event.
 
@@ -298,7 +311,7 @@ class QEMUMonitorProtocol:
             return self.__events.pop(0)
         return None
 
-    def get_events(self, wait=False):
+    def get_events(self, wait: bool = False) -> List[QMPMessage]:
         """
         Get a list of available QMP events.
 
@@ -315,13 +328,13 @@ class QEMUMonitorProtocol:
         self.__get_events(wait)
         return self.__events
 
-    def clear_events(self):
+    def clear_events(self) -> None:
         """
         Clear current list of pending events.
         """
         self.__events = []
 
-    def close(self):
+    def close(self) -> None:
         """
         Close the socket and socket file.
         """
@@ -330,16 +343,22 @@ class QEMUMonitorProtocol:
         if self.__sockfile:
             self.__sockfile.close()
 
-    def settimeout(self, timeout):
+    def settimeout(self, timeout: Optional[float]) -> None:
         """
         Set the socket timeout.
 
-        @param timeout (float): timeout in seconds, or None.
+        @param timeout (float): timeout in seconds (non-zero), or None.
         @note This is a wrap around socket.settimeout
+
+        @raise ValueError: if timeout was set to 0.
         """
+        if timeout == 0:
+            msg = "timeout cannot be 0; this engages non-blocking mode."
+            msg += " Use 'None' instead to disable timeouts."
+            raise ValueError(msg)
         self.__sock.settimeout(timeout)
 
-    def get_sock_fd(self):
+    def get_sock_fd(self) -> int:
         """
         Get the socket file descriptor.
 
@@ -347,7 +366,7 @@ class QEMUMonitorProtocol:
         """
         return self.__sock.fileno()
 
-    def is_scm_available(self):
+    def is_scm_available(self) -> bool:
         """
         Check if the socket allows for SCM_RIGHTS.
 
diff --git a/python/qemu/qtest.py b/python/qemu/qtest.py
index 888c8bd..39a0cf6 100644
--- a/python/qemu/qtest.py
+++ b/python/qemu/qtest.py
@@ -17,11 +17,17 @@ subclass of QEMUMachine, respectively.
 # Based on qmp.py.
 #
 
-import socket
 import os
-from typing import Optional, TextIO
+import socket
+from typing import (
+    List,
+    Optional,
+    Sequence,
+    TextIO,
+)
 
 from .machine import QEMUMachine
+from .qmp import SocketAddrT
 
 
 class QEMUQtestProtocol:
@@ -38,7 +44,8 @@ class QEMUQtestProtocol:
        No conection is estabalished by __init__(), this is done
        by the connect() or accept() methods.
     """
-    def __init__(self, address, server=False):
+    def __init__(self, address: SocketAddrT,
+                 server: bool = False):
         self._address = address
         self._sock = self._get_sock()
         self._sockfile: Optional[TextIO] = None
@@ -46,14 +53,14 @@ class QEMUQtestProtocol:
             self._sock.bind(self._address)
             self._sock.listen(1)
 
-    def _get_sock(self):
+    def _get_sock(self) -> socket.socket:
         if isinstance(self._address, tuple):
             family = socket.AF_INET
         else:
             family = socket.AF_UNIX
         return socket.socket(family, socket.SOCK_STREAM)
 
-    def connect(self):
+    def connect(self) -> None:
         """
         Connect to the qtest socket.
 
@@ -62,7 +69,7 @@ class QEMUQtestProtocol:
         self._sock.connect(self._address)
         self._sockfile = self._sock.makefile(mode='r')
 
-    def accept(self):
+    def accept(self) -> None:
         """
         Await connection from QEMU.
 
@@ -71,7 +78,7 @@ class QEMUQtestProtocol:
         self._sock, _ = self._sock.accept()
         self._sockfile = self._sock.makefile(mode='r')
 
-    def cmd(self, qtest_cmd):
+    def cmd(self, qtest_cmd: str) -> str:
         """
         Send a qtest command on the wire.
 
@@ -82,14 +89,16 @@ class QEMUQtestProtocol:
         resp = self._sockfile.readline()
         return resp
 
-    def close(self):
-        """Close this socket."""
+    def close(self) -> None:
+        """
+        Close this socket.
+        """
         self._sock.close()
         if self._sockfile:
             self._sockfile.close()
             self._sockfile = None
 
-    def settimeout(self, timeout):
+    def settimeout(self, timeout: Optional[float]) -> None:
         """Set a timeout, in seconds."""
         self._sock.settimeout(timeout)
 
@@ -99,8 +108,13 @@ class QEMUQtestMachine(QEMUMachine):
     A QEMU VM, with a qtest socket available.
     """
 
-    def __init__(self, binary, args=None, name=None, test_dir="/var/tmp",
-                 socket_scm_helper=None, sock_dir=None):
+    def __init__(self,
+                 binary: str,
+                 args: Sequence[str] = (),
+                 name: Optional[str] = None,
+                 test_dir: str = "/var/tmp",
+                 socket_scm_helper: Optional[str] = None,
+                 sock_dir: Optional[str] = None):
         if name is None:
             name = "qemu-%d" % os.getpid()
         if sock_dir is None:
@@ -108,16 +122,19 @@ class QEMUQtestMachine(QEMUMachine):
         super().__init__(binary, args, name=name, test_dir=test_dir,
                          socket_scm_helper=socket_scm_helper,
                          sock_dir=sock_dir)
-        self._qtest = None
+        self._qtest: Optional[QEMUQtestProtocol] = None
         self._qtest_path = os.path.join(sock_dir, name + "-qtest.sock")
 
-    def _base_args(self):
-        args = super()._base_args()
-        args.extend(['-qtest', 'unix:path=' + self._qtest_path,
-                     '-accel', 'qtest'])
+    @property
+    def _base_args(self) -> List[str]:
+        args = super()._base_args
+        args.extend([
+            '-qtest', f"unix:path={self._qtest_path}",
+            '-accel', 'qtest'
+        ])
         return args
 
-    def _pre_launch(self):
+    def _pre_launch(self) -> None:
         super()._pre_launch()
         self._qtest = QEMUQtestProtocol(self._qtest_path, server=True)
 
@@ -126,7 +143,7 @@ class QEMUQtestMachine(QEMUMachine):
         super()._post_launch()
         self._qtest.accept()
 
-    def _post_shutdown(self):
+    def _post_shutdown(self) -> None:
         super()._post_shutdown()
         self._remove_if_exists(self._qtest_path)
 
diff --git a/tests/qemu-iotests/iotests.py b/tests/qemu-iotests/iotests.py
index f212cec..63d2ace 100644
--- a/tests/qemu-iotests/iotests.py
+++ b/tests/qemu-iotests/iotests.py
@@ -605,7 +605,7 @@ class VM(qtest.QEMUQtestMachine):
 
     def hmp(self, command_line: str, use_log: bool = False) -> QMPMessage:
         cmd = 'human-monitor-command'
-        kwargs = {'command-line': command_line}
+        kwargs: Dict[str, Any] = {'command-line': command_line}
         if use_log:
             return self.qmp_log(cmd, **kwargs)
         else: