python/qemu: Add ConsoleSocket for optional use in QEMUMachine

We add the ConsoleSocket object, which has a socket interface
and which will consume all arriving characters on the
socket, placing them into an in memory buffer.
This will also provide those chars via recv() as
would a regular socket.
ConsoleSocket also has the option of dumping
the console bytes to a log file.

We also give QEMUMachine the option of using ConsoleSocket
to drain and to use for logging console to a file.
By default QEMUMachine does not use ConsoleSocket.

This is added in preparation for use by basevm.py in a later commit.
This is a workaround we found was needed for basevm.py since
there is a known issue where QEMU will hang waiting
for console characters to be consumed.

Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Cleber Rosa <crosa@redhat.com>
Signed-off-by: Robert Foley <robert.foley@linaro.org>
Reviewed-by: Peter Puhov <peter.puhov@linaro.org>
Acked-by: Alex Bennée <alex.bennee@linaro.org>
Tested-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20200601211421.1277-9-robert.foley@linaro.org>
Message-Id: <20200701135652.1366-13-alex.bennee@linaro.org>

python/qemu/machine.py

@@ -26,6 +26,7 @@ import socket
 import tempfile
 from typing import Optional, Type
 from types import TracebackType
+from qemu.console_socket import ConsoleSocket
 
 from . import qmp
 
@@ -75,7 +76,8 @@ class QEMUMachine:
 
     def __init__(self, binary, args=None, wrapper=None, name=None,
                  test_dir="/var/tmp", monitor_address=None,
-                 socket_scm_helper=None, sock_dir=None):
+                 socket_scm_helper=None, sock_dir=None,
+                 drain_console=False, console_log=None):
         '''
         Initialize a QEMUMachine
 
@@ -86,6 +88,9 @@ class QEMUMachine:
         @param test_dir: where to create socket and log file
         @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
         @note: Qemu process is not started until launch() is used.
         '''
         if args is None:
@@ -122,6 +127,12 @@ class QEMUMachine:
         self._console_address = None
         self._console_socket = None
         self._remove_files = []
+        self._console_log_path = console_log
+        if self._console_log_path:
+            # In order to log the console, buffering needs to be enabled.
+            self._drain_console = True
+        else:
+            self._drain_console = drain_console
 
     def __enter__(self):
         return self
@@ -580,7 +591,11 @@ class QEMUMachine:
         Returns a socket connected to the console
         """
         if self._console_socket is None:
-            self._console_socket = socket.socket(socket.AF_UNIX,
-                                                 socket.SOCK_STREAM)
-            self._console_socket.connect(self._console_address)
+            if self._drain_console:
+                self._console_socket = ConsoleSocket(self._console_address,
+                                                    file=self._console_log_path)
+            else:
+                self._console_socket = socket.socket(socket.AF_UNIX,
+                                                     socket.SOCK_STREAM)
+                self._console_socket.connect(self._console_address)
         return self._console_socket