virtio-serial:Under named-pipe non-blocking testing

Signed-off-by: NNana Liu <nanliu@redhat.com>

qemu/tests/cfg/virtio_trace_pipenb.cfg

+- virtio_trace_pipenb:
+    only Linux
+    type = virtio_trace_pipenb
+    smp = 1
+    serials += " vs2"
+    serial_type_vs2 = virtserialport
+    chardev_backend_vs2 = pipe

qemu/tests/virtio_trace_pipenb.py

+import time
+import os
+import errno
+
+from virttest import error_context
+
+
+@error_context.context_aware
+def run(test, params, env):
+    """
+    Under named-pipe non-blocking testing:
+    1) Create pipe named by the following
+    2) Boot up a single-CPU guest with a virtio-serial device and
+       named-pipe chardev backend
+    3) Write data to the virtio-serial port until the guest stops.
+    4) check whether guest can work.
+    5) Read the named-pipe file on the host.
+
+    :param test: QEMU test object
+    :param params: Dictionary with the test parameters
+    :param env: Dictionary with test environment.
+    """
+    timeout = float(params.get("login_timeout", 360))
+    vm = env.get_vm(params["main_vm"])
+    serials = params["serials"].split()
+    v_path = vm.get_serial_console_filename(serials[-1])
+    vm.verify_alive()
+    session = vm.wait_for_login(timeout=timeout)
+    out_put = session.cmd_output("nohup cat /proc/kallsyms > /dev/virtio-ports/vs2 2>&1 &")
+    time.sleep(10)
+    if session.cmd_output("date") is None:
+        test.fail("Guest shouldn't be blocked and a date should output!")
+    guest_pid = out_put.split()[1]
+    pipe = os.open(v_path, os.O_RDONLY | os.O_NONBLOCK)
+    while True:
+        try:
+            os.read(pipe, 1)
+        except OSError as e:
+            if e.errno == errno.EAGAIN or e.errno == errno.EWOULDBLOCK:
+                time.sleep(5)
+                break
+            else:
+                raise Exception("Read data in host failed as %s" % e)
+
+    if not session.cmd_status("ps -p %s" % guest_pid, safe=True):
+        test.fail("send process in guest does not exit after all data are read out in host")
+    vm.verify_alive()
+    vm.verify_kernel_crash()