Re: [Qemu-devel] [PATCH RFC 4/9] tests: Add vm test lib

[Stefan Hajnoczi]

On Wed, Aug 16, 2017 at 03:20:59PM +0800, Fam Zheng wrote:
> +class BaseVM(object):
> +    GUEST_USER = "qemu"
> +    GUEST_PASS = "qemupass"
> +    ROOT_PASS = "qemupass"
> +
> +    # The script to run in the guest that builds QEMU
> +    BUILD_SCRIPT = ""
> +    # The guest name, to be overridden by subclasses
> +    name = "#base"
> +    def __init__(self, debug=False):
> +        self._guest = None
> +        self.ssh_port = 20022

Only one instance of this test can be run per machine due to the
hardcoded SSH port number on the host.

It is possible to use:

  -netdev user,id=vnet,hostfwd=:0.0.0.0:0-:22

and then query the port number:

  (qemu) info usernet
  VLAN -1 (vnet):
  Protocol[State]    FD  Source Address  Port   Dest. Address  Port RecvQ SendQ
  TCP[HOST_FORWARD]  15               * 36089       10.0.2.15    22     0     0

The host port is 36089 in this example.

I'm not aware of a QMP equivalent for "info usernet".  It may be
necessary to implement a query-usernet command if you don't want to use
HMP.

> +        self._tmpdir = tempfile.mkdtemp(prefix="qemu-vm-")
> +        atexit.register(shutil.rmtree, self._tmpdir)
> +
> +        self._ssh_key_file = os.path.join(self._tmpdir, "id_rsa")
> +        open(self._ssh_key_file, "w").write(SSH_KEY)
> +        subprocess.check_call(["chmod", "600", self._ssh_key_file])
> +
> +        self._ssh_pub_key_file = os.path.join(self._tmpdir, "id_rsa.pub")
> +        open(self._ssh_pub_key_file, "w").write(SSH_PUB_KEY)
> +
> +        self.debug = debug
> +        self._stderr = sys.stderr
> +        self._devnull = open("/dev/null", "w")
> +        if self.debug:
> +            self._stdout = sys.stdout
> +        else:
> +            self._stdout = self._devnull
> +        self._args = [ \
> +            "-nodefaults", "-enable-kvm", "-m", "2G",
> +            "-smp", os.environ.get("J", "4"), "-cpu", "host",

Can this be a command-line option in main() and a constructor argument
instead of an environment variable?  That would be cleaner because the
use of "J" might be surprising to someone who happens to have it set in
their environment.

> +            "-netdev", "user,id=vnet,hostfwd=:0.0.0.0:%d-:22" % 
> self.ssh_port,
> +            "-device", "virtio-net-pci,netdev=vnet",
> +            "-vnc", ":0,to=20",
> +            "-serial", "file:%s" % os.path.join(self._tmpdir, "serial.out")]
> +
> +        self._data_args = []
> +
> +    def _download_with_cache(self, url):
> +        cache_dir = os.path.expanduser("~/.cache/qemu-vm/download")
> +        subprocess.check_call(["mkdir", "-p", cache_dir])

os.makedirs()

> +        fname = os.path.join(cache_dir, hashlib.sha1(url).hexdigest())
> +        if os.path.exists(fname):
> +            return fname
> +        logging.debug("Downloading %s to %s...", url, fname)
> +        subprocess.check_call(["wget", "-c", url, "-O", fname + ".download"],
> +                              stdout=self._stdout, stderr=self._stderr)

It might be important to support image file updates without manually
deleting ~/.cache.  You can probably make wget send an HTTP
If-Modified-Since header or something similar.  There are 3 cases:

1. Existing file is up-to-date.  No download after HEAD request.
2. Existing file is outdated, download the newest version.
3. Failure or timeout, use the old version for now.

> +        subprocess.check_call(["mv", fname + ".download", fname],
> +                              stdout=self._stdout, stderr=self._stderr)

os.rename()

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