tests/acceptance: introduce arch parameter and attribute

It's useful to define the architecture that should be used in
situations such as:
 * the intended target of the QEMU binary to be used on tests
 * the architecture of code to be run within the QEMU binary, such
   as a kernel image or a full blown guest OS image

This commit introduces both a test parameter and a test instance
attribute, that will contain such a value.

Now, when the "arch" test parameter is given, it will influence the
selection of the default QEMU binary, if one is not given explicitly
by means of the "qemu_img" parameter.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Message-Id: <20190312171824.5134-5-crosa@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

2 files changed, 39 insertions, 3 deletions

diff --git a/docs/devel/testing.rst b/docs/devel/testing.rst
index 7c1b199323..83bf9f09ac 100644
--- a/docs/devel/testing.rst
+++ b/docs/devel/testing.rst
@@ -727,6 +727,21 @@ vm
 A QEMUMachine instance, initially configured according to the given
 ``qemu_bin`` parameter.
 
+arch
+~~~~
+
+The architecture can be used on different levels of the stack, e.g. by
+the framework or by the test itself.  At the framework level, it will
+currently influence the selection of a QEMU binary (when one is not
+explicitly given).
+
+Tests are also free to use this attribute value, for their own needs.
+A test may, for instance, use the same value when selecting the
+architecture of a kernel or disk image to boot a VM with.
+
+The ``arch`` attribute will be set to the test parameter of the same
+name, and if one is not given explicitly, it will be set to ``None``.
+
 qemu_bin
 ~~~~~~~~
 
@@ -749,6 +764,19 @@ like the following:
 
   PARAMS (key=qemu_bin, path=*, default=x86_64-softmmu/qemu-system-x86_64) => 'x86_64-softmmu/qemu-system-x86_64
 
+arch
+~~~~
+
+The architecture that will influence the selection of a QEMU binary
+(when one is not explicitly given).
+
+Tests are also free to use this parameter value, for their own needs.
+A test may, for instance, use the same value when selecting the
+architecture of a kernel or disk image to boot a VM with.
+
+This parameter has a direct relation with the ``arch`` attribute.  If
+not given, it will default to None.
+
 qemu_bin
 ~~~~~~~~
 
diff --git a/tests/acceptance/avocado_qemu/__init__.py b/tests/acceptance/avocado_qemu/__init__.py
index b7c5d598d8..688a0746a2 100644
--- a/tests/acceptance/avocado_qemu/__init__.py
+++ b/tests/acceptance/avocado_qemu/__init__.py
@@ -23,16 +23,22 @@ def is_readable_executable_file(path):
     return os.path.isfile(path) and os.access(path, os.R_OK | os.X_OK)
 
 
-def pick_default_qemu_bin():
+def pick_default_qemu_bin(arch=None):
     """
     Picks the path of a QEMU binary, starting either in the current working
     directory or in the source tree root directory.
 
+    :param arch: the arch to use when looking for a QEMU binary (the target
+                 will match the arch given).  If None (the default), arch
+                 will be the current host system arch (as given by
+                 :func:`os.uname`).
+    :type arch: str
     :returns: the path to the default QEMU binary or None if one could not
               be found
     :rtype: str or None
     """
-    arch = os.uname()[4]
+    if arch is None:
+        arch = os.uname()[4]
     qemu_bin_relative_path = os.path.join("%s-softmmu" % arch,
                                           "qemu-system-%s" % arch)
     if is_readable_executable_file(qemu_bin_relative_path):
@@ -47,8 +53,10 @@ def pick_default_qemu_bin():
 class Test(avocado.Test):
     def setUp(self):
         self._vms = {}
+        self.arch = self.params.get('arch')
+        default_qemu_bin = pick_default_qemu_bin(arch=self.arch)
         self.qemu_bin = self.params.get('qemu_bin',
-                                        default=pick_default_qemu_bin())
+                                        default=default_qemu_bin)
         if self.qemu_bin is None:
             self.cancel("No QEMU binary defined or found in the source tree")