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

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

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 <wainersm@redhat.com>
>>> ---
>>>   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
>>>
>>
>