Merge remote-tracking branch 'remotes/philmd-gitlab/tags/python-next-20200714' into staging

Python patches for 5.1

- Reduce race conditions on QEMUMachine::shutdown()

 1. Remove the "bare except" pattern in the existing shutdown code,
    which can mask problems and make debugging difficult.
 2. Ensure that post-shutdown cleanup is always performed, even when
    graceful termination fails.
 3. Unify cleanup paths such that no matter how the VM is terminated,
    the same functions and steps are always taken to reset the object
    state.
 4. Rewrite shutdown() such that any error encountered when attempting
    a graceful shutdown will be raised as an AbnormalShutdown exception.
    The pythonic idiom is to allow the caller to decide if this is a
    problem or not.

- Modify part of the python/qemu library to comply with:

  . mypy --strict
  . pylint
  . flake8

- Script for the TCG Continuous Benchmarking project that uses
  callgrind to dissect QEMU execution into three main phases:

  . code generation
  . JIT execution
  . helpers execution

CI jobs results:
. https://cirrus-ci.com/build/5421349961203712
. https://gitlab.com/philmd/qemu/-/pipelines/166556001
. https://travis-ci.org/github/philmd/qemu/builds/708102347

# gpg: Signature made Tue 14 Jul 2020 21:40:05 BST
# gpg:                using RSA key FAABE75E12917221DCFD6BB2E3E32C2CDEADC0DE
# gpg: Good signature from "Philippe Mathieu-Daudé (F4BUG) <f4bug@amsat.org>" [full]
# Primary key fingerprint: FAAB E75E 1291 7221 DCFD  6BB2 E3E3 2C2C DEAD C0DE

* remotes/philmd-gitlab/tags/python-next-20200714:
  python/qmp.py: add QMPProtocolError
  python/qmp.py: add casts to JSON deserialization
  python/qmp.py: Do not return None from cmd_obj
  python/qmp.py: re-absorb MonitorResponseError
  iotests.py: use qemu.qmp type aliases
  python/qmp.py: Define common types
  python/machine.py: change default wait timeout to 3 seconds
  python/machine.py: re-add sigkill warning suppression
  python/machine.py: split shutdown into hard and soft flavors
  tests/acceptance: Don't test reboot on cubieboard
  tests/acceptance: wait() instead of shutdown() where appropriate
  python/machine.py: Make wait() call shutdown()
  python/machine.py: Add a configurable timeout to shutdown()
  python/machine.py: Prohibit multiple shutdown() calls
  python/machine.py: Perform early cleanup for wait() calls, too
  python/machine.py: Add _early_cleanup hook
  python/machine.py: Close QMP socket in cleanup
  python/machine.py: consolidate _post_shutdown()
  scripts/performance: Add dissect.py script

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

1 files changed, 54 insertions, 13 deletions

diff --git a/python/qemu/qmp.py b/python/qemu/qmp.py
index e64b6b5faa..7935dababb 100644
--- a/python/qemu/qmp.py
+++ b/python/qemu/qmp.py
@@ -12,13 +12,32 @@ import errno
 import socket
 import logging
 from typing import (
+    Any,
+    cast,
+    Dict,
     Optional,
     TextIO,
     Type,
+    Tuple,
+    Union,
 )
 from types import TracebackType
 
 
+# QMPMessage is a QMP Message of any kind.
+# e.g. {'yee': 'haw'}
+#
+# QMPReturnValue is the inner value of return values only.
+# {'return': {}} is the QMPMessage,
+# {} is the QMPReturnValue.
+QMPMessage = Dict[str, Any]
+QMPReturnValue = Dict[str, Any]
+
+InternetAddrT = Tuple[str, str]
+UnixAddrT = str
+SocketAddrT = Union[InternetAddrT, UnixAddrT]
+
+
 class QMPError(Exception):
     """
     QMP base exception
@@ -43,6 +62,25 @@ class QMPTimeoutError(QMPError):
     """
 
 
+class QMPProtocolError(QMPError):
+    """
+    QMP protocol error; unexpected response
+    """
+
+
+class QMPResponseError(QMPError):
+    """
+    Represents erroneous QMP monitor reply
+    """
+    def __init__(self, reply: QMPMessage):
+        try:
+            desc = reply['error']['desc']
+        except KeyError:
+            desc = reply
+        super().__init__(desc)
+        self.reply = reply
+
+
 class QEMUMonitorProtocol:
     """
     Provide an API to connect to QEMU via QEMU Monitor Protocol (QMP) and then
@@ -99,7 +137,10 @@ class QEMUMonitorProtocol:
             data = self.__sockfile.readline()
             if not data:
                 return None
-            resp = json.loads(data)
+            # By definition, any JSON received from QMP is a QMPMessage,
+            # and we are asserting only at static analysis time that it
+            # has a particular shape.
+            resp: QMPMessage = json.loads(data)
             if 'event' in resp:
                 self.logger.debug("<<< %s", resp)
                 self.__events.append(resp)
@@ -194,22 +235,18 @@ class QEMUMonitorProtocol:
         self.__sockfile = self.__sock.makefile(mode='r')
         return self.__negotiate_capabilities()
 
-    def cmd_obj(self, qmp_cmd):
+    def cmd_obj(self, qmp_cmd: QMPMessage) -> QMPMessage:
         """
         Send a QMP command to the QMP Monitor.
 
         @param qmp_cmd: QMP command to be sent as a Python dict
-        @return QMP response as a Python dict or None if the connection has
-                been closed
+        @return QMP response as a Python dict
         """
         self.logger.debug(">>> %s", qmp_cmd)
-        try:
-            self.__sock.sendall(json.dumps(qmp_cmd).encode('utf-8'))
-        except OSError as err:
-            if err.errno == errno.EPIPE:
-                return None
-            raise err
+        self.__sock.sendall(json.dumps(qmp_cmd).encode('utf-8'))
         resp = self.__json_read()
+        if resp is None:
+            raise QMPConnectError("Unexpected empty reply from server")
         self.logger.debug("<<< %s", resp)
         return resp
 
@@ -233,9 +270,13 @@ class QEMUMonitorProtocol:
         Build and send a QMP command to the monitor, report errors if any
         """
         ret = self.cmd(cmd, kwds)
-        if "error" in ret:
-            raise Exception(ret['error']['desc'])
-        return ret['return']
+        if 'error' in ret:
+            raise QMPResponseError(ret)
+        if 'return' not in ret:
+            raise QMPProtocolError(
+                "'return' key not found in QMP response '{}'".format(str(ret))
+            )
+        return cast(QMPReturnValue, ret['return'])
 
     def pull_event(self, wait=False):
         """