virtio_page_per_vq: enhance input event file

Regarding /dev/input/event* files, there might be some different
situation.
For example,
- No event file exsit at all
- Only /dev/input/event0 exists
- Only /dev/input/event1 exists
- Both /dev/input/event0 and /dev/input/event1 exists
- and more ...

So this patch is intending to support above situations instead of
hardcoding with event1.

Signed-off-by: Dan Zheng <[email protected]>

libvirt/tests/cfg/virtio/virtio_page_per_vq.cfg

@@ -41,7 +41,7 @@
                 - mouse:
                 - tablet:
                 - passthrough:
-                    device_dict = {**${device_dict}, 'source_evdev': '/dev/input/event1'}
+                    device_dict = {**${device_dict}, 'source_evdev': '%s'}
         - video:
             only default_start
             device_dict = {'model_type': 'virtio', **${driver_dict}, 'model_heads': '1'}

libvirt/tests/src/virtio/virtio_page_per_vq.py

@@ -1,6 +1,8 @@
 import os
 import platform
 
+from avocado.utils import process
+
 from virttest import libvirt_version
 from virttest import utils_net
 from virttest import virsh
@@ -17,6 +19,24 @@
 from virttest.utils_test import libvirt
 
 
+def get_input_event_file(test):
+    """
+    Get the input event file on the host
+
+    :return: str, the last file path if exists, otherwise skip the test
+    """
+    ret = process.run("ls /dev/input/event*",
+                      shell=True,
+                      verbose=True,
+                      ignore_status=True)
+    if ret.exit_status != 0:
+        if ret.stderr_text.count("No such file or directory"):
+            test.cancel(ret.stderr_text)
+        else:
+            test.fail(ret.stderr_text)
+    return ret.stdout_text.splitlines()[-1]
+
+
 def run(test, params, env):
     """
     Start guest with virtio page_per_vq attribute - various virtio devices
@@ -55,6 +75,8 @@ def prepare_test(vmxml):
             device_dict['source']['attrs']['file'] = disk_image_path
         if device_type == "input":
             device_xml = eval(device_obj)(input_type)
+            if input_type == "passthrough":
+                device_dict['source_evdev'] = get_input_event_file(test)
         else:
             device_xml = eval(device_obj)()
         device_xml.setup_attrs(**device_dict)