Re: [PATCH v3 3/3] python/qemu/machine: use socketpair() for QMP by default

[John Snow]

On Wed, Jan 11, 2023 at 3:01 AM <marcandre.lureau@redhat.com> wrote:
>
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
>
> When no monitor address is given, establish the QMP communication through
> a socketpair() (API is also supported on Windows since Python 3.5)
>
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>  python/qemu/machine/machine.py | 24 ++++++++++++++++--------
>  1 file changed, 16 insertions(+), 8 deletions(-)
>
> diff --git a/python/qemu/machine/machine.py b/python/qemu/machine/machine.py
> index 748a0d807c..5b2e499e68 100644
> --- a/python/qemu/machine/machine.py
> +++ b/python/qemu/machine/machine.py
> @@ -158,17 +158,13 @@ def __init__(self,
>          self._qmp_timer = qmp_timer
>
>          self._name = name or f"qemu-{os.getpid()}-{id(self):02x}"
> +        self._sock_pair: Optional[Tuple[socket.socket, socket.socket]] = None
>          self._temp_dir: Optional[str] = None
>          self._base_temp_dir = base_temp_dir
>          self._sock_dir = sock_dir
>          self._log_dir = log_dir
>
> -        if monitor_address is not None:
> -            self._monitor_address = monitor_address
> -        else:
> -            self._monitor_address = os.path.join(
> -                self.sock_dir, f"{self._name}-monitor.sock"
> -            )
> +        self._monitor_address = monitor_address
>
>          self._console_log_path = console_log
>          if self._console_log_path:
> @@ -303,7 +299,11 @@ def _base_args(self) -> List[str]:
>          args = ['-display', 'none', '-vga', 'none']
>
>          if self._qmp_set:
> -            if isinstance(self._monitor_address, tuple):
> +            if self._sock_pair:
> +                fd = self._sock_pair[0].fileno()
> +                os.set_inheritable(fd, True)
> +                moncdev = f"socket,id=mon,fd={fd}"
> +            elif isinstance(self._monitor_address, tuple):
>                  moncdev = "socket,id=mon,host={},port={}".format(
>                      *self._monitor_address
>                  )
> @@ -337,10 +337,17 @@ def _pre_launch(self) -> None:
>              self._remove_files.append(self._console_address)
>
>          if self._qmp_set:
> +            monitor_address = None
> +            sock = None
> +            if self._monitor_address is None:
> +                self._sock_pair = socket.socketpair()
> +                sock = self._sock_pair[1]
>              if isinstance(self._monitor_address, str):
>                  self._remove_files.append(self._monitor_address)
> +                monitor_address = self._monitor_address
>              self._qmp_connection = QEMUMonitorProtocol(
> -                self._monitor_address,
> +                address=monitor_address,
> +                sock=sock,
>                  server=True,
>                  nickname=self._name
>              )
> @@ -360,6 +367,7 @@ def _pre_launch(self) -> None:
>          ))
>
>      def _post_launch(self) -> None:
> +        self._sock_pair[0].close()

Needs an assert or an error-check here for _sock_pair to be non-None,
otherwise mypy will shout. Try running "make check-dev" from
qemu.git/python directory as a smoke test.


>          if self._qmp_connection:
>              self._qmp.accept(self._qmp_timer)
>
> --
> 2.39.0
>