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Re: [PATCH v3 1/4] tests/acceptance: avocado_qemu: Introduce the 'accel'


From: Philippe Mathieu-Daudé
Subject: Re: [PATCH v3 1/4] tests/acceptance: avocado_qemu: Introduce the 'accel' test parameter
Date: Thu, 30 Jan 2020 23:51:22 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2

On 1/27/20 8:28 PM, Wainer dos Santos Moschetta wrote:
On 1/24/20 7:36 AM, Philippe Mathieu-Daudé wrote:
On 1/22/20 2:27 AM, Wainer dos Santos Moschetta wrote:
The test case may need to boot the VM with an accelerator that
isn't actually enabled on the QEMU binary and/or present in the host. In
this case the test behavior is undefined, and the best course of
action is to skip its execution.

This change introduced the 'accel' parameter (and the handler of
tag with same name) used to indicate the test case requires a
given accelerator available. It was implemented a mechanism to
skip the test case if the accelerator is not available. Moreover,
  the QEMU -accel argument is set automatically to any VM
launched if the parameter is present.

Signed-off-by: Wainer dos Santos Moschetta <address@hidden>
---
  docs/devel/testing.rst                    | 16 ++++++++++++++++
  tests/acceptance/avocado_qemu/__init__.py | 23 +++++++++++++++++++++++
  2 files changed, 39 insertions(+)

diff --git a/docs/devel/testing.rst b/docs/devel/testing.rst
index ab5be0c729..d17d0e90aa 100644
--- a/docs/devel/testing.rst
+++ b/docs/devel/testing.rst
@@ -759,6 +759,17 @@ name.  If one is not given explicitly, it will either be set to
  ``None``, or, if the test is tagged with one (and only one)
  ``:avocado: tags=machine:VALUE`` tag, it will be set to ``VALUE``.
  +accel
+~~~~~
+The accelerator that will be set to all QEMUMachine instances created
+by the test.
+
+The ``accel`` attribute will be set to the test parameter of the same
+name.  If one is not given explicitly, it will either be set to
+``None``, or, if the test is tagged with one (and only one)
+``:avocado: tags=accel:VALUE`` tag, it will be set to ``VALUE``. Currently
+``VALUE`` should be either ``kvm`` or ``tcg``.
+
  qemu_bin
  ~~~~~~~~
  @@ -800,6 +811,11 @@ machine
  The machine type that will be set to all QEMUMachine instances created
  by the test.
  +accel
+~~~~~
+The accelerator that will be set to all QEMUMachine instances created
+by the test. In case the accelerator is not available (both QEMU
+binary and the host system are checked) then the test is canceled.
    qemu_bin
  ~~~~~~~~
diff --git a/tests/acceptance/avocado_qemu/__init__.py b/tests/acceptance/avocado_qemu/__init__.py
index 6618ea67c1..c83a75ccbc 100644
--- a/tests/acceptance/avocado_qemu/__init__.py
+++ b/tests/acceptance/avocado_qemu/__init__.py
@@ -20,6 +20,7 @@ SRC_ROOT_DIR = os.path.join(os.path.dirname(__file__), '..', '..', '..')
  sys.path.append(os.path.join(SRC_ROOT_DIR, 'python'))
    from qemu.machine import QEMUMachine
+from qemu.accel import kvm_available, tcg_available
    def is_readable_executable_file(path):
      return os.path.isfile(path) and os.access(path, os.R_OK | os.X_OK)
@@ -111,6 +112,8 @@ class Test(avocado.Test):
        def setUp(self):
          self._vms = {}
+        # VM argumments that are mapped from parameters
+        self._param_to_vm_args = []
            self.arch = self.params.get('arch',
default=self._get_unique_tag_val('arch'))
@@ -124,10 +127,30 @@ class Test(avocado.Test):
          if self.qemu_bin is None:
              self.cancel("No QEMU binary defined or found in the source tree")
  +        self.accel = self.params.get('accel',
+ default=self._get_unique_tag_val('accel'))
+        if self.accel:
+            avail = False
+            if self.accel == 'kvm':
+                if kvm_available(self.arch, self.qemu_bin):
+                    avail = True
+            elif self.accel == 'tcg':
+                if tcg_available(self.qemu_bin):
+                    avail = True
+            else:
+                self.cancel("Unknown accelerator: %s" % self.accel)
+
+            if avail:
+                self._param_to_vm_args.extend(['-accel', self.accel])
+            else:
+                self.cancel("%s is not available" % self.accel)

Why refuse to test the other accelerators?

Isn't it better to QMP-ask QEMU which accelerator it supports, and SKIP if it isn't available?


python/qemu/accel.py:list_accel(qemu_bin) can be used for that end. For example:

if self.accel not in list_accel(self.qemu_bin):

     self.cancel("%s is not available" % self.accel)

However checking the support only on QEMU's binary may be very weak (take KVM as an example). I implemented checkers for kvm and tcg on python/qemu/accel.py. Given that I have zero knowledge on the other accelerators,  I simply did not touch on them.

That said, IMHO it needs to implement checkers for those others accelerator before they get reliably handled by avocado_qemu automatically. And test writers can still run tests with those accelerators as long as 'accel' tag is not used.

What do you think Philippe?

Can you have a look at the binary_get_accels() method which aims to be more generic?

https://lists.gnu.org/archive/html/qemu-devel/2020-01/msg07312.html
"python/qemu: Add binutils::binary_get_accels()"

https://lists.gnu.org/archive/html/qemu-devel/2020-01/msg07313.html
"python/qemu/accel: Use binutils::binary_get_accels()"


Thanks, good point!

- Wainer




+
      def _new_vm(self, *args):
          vm = QEMUMachine(self.qemu_bin, sock_dir=tempfile.mkdtemp())
          if args:
              vm.add_args(*args)
+        if self._param_to_vm_args:
+            vm.add_args(*self._param_to_vm_args)
          return vm
        @property







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