Re: [Qemu-devel] [PATCH] Acceptance tests: host arch to target arch name mapping

[Eduardo Habkost]

On Wed, Oct 17, 2018 at 07:17:25PM -0400, Cleber Rosa wrote:
> 
> 
> On 10/17/18 6:12 PM, Eduardo Habkost wrote:
> > On Wed, Oct 17, 2018 at 04:54:52PM -0400, Cleber Rosa wrote:
> >>
> >>
> >> On 10/17/18 3:48 PM, Eduardo Habkost wrote:
> >>> On Wed, Oct 17, 2018 at 03:25:34PM -0400, Cleber Rosa wrote:
> >>>>
> >>>>
> >>>> On 10/17/18 3:09 PM, Eduardo Habkost wrote:
> >>>>> On Wed, Oct 17, 2018 at 07:40:51PM +0100, Peter Maydell wrote:
> >>>>>> On 17 October 2018 at 18:38, Cleber Rosa <address@hidden> wrote:
> >>>>>>>
> >>>>>>>
> >>>>>>> On 10/17/18 12:29 PM, Eduardo Habkost wrote:
> >>>>>>>> On Wed, Oct 17, 2018 at 01:34:41PM +0100, Peter Maydell wrote:
> >>>>>>>>> So, why does the test code need to care? It's not clear
> >>>>>>>>> from the patch... My expectation would be that you'd
> >>>>>>>>> just test all the testable target architectures,
> >>>>>>>>> regardless of what the host architecture is.
> >>>>>>>>
> >>>>>>>> I tend to agree.  Maybe the right solution is to get rid of the
> >>>>>>>> os.uname().  I think the default should be testing all QEMU
> >>>>>>>> binaries that were built, and the host architecture shouldn't
> >>>>>>>> matter.
> >>>>>>
> >>>>>> Yes, looking at os.uname() also seems like an odd thing
> >>>>>> for the tests to be doing here. The test framework
> >>>>>> should be as far as possible host-architecture agnostic.
> >>>>>> (For some of the KVM cases there probably is a need to
> >>>>>> care, but those are exceptions, not the rule.)
> >>>>>>
> >>>>>>> I'm in favor of exercising all built targets, but that seems to me to 
> >>>>>>> be
> >>>>>>> on another layer, above the test themselves. This change is about the
> >>>>>>> behavior of a test when not told about the target arch (and thus 
> >>>>>>> binary)
> >>>>>>> it should use.
> >>>>>>
> >>>>>> At that level, I think the right answer is "tell the user
> >>>>>> they need to specify the qemu executable they are trying to test".
> >>>>>> In particular, there is no guarantee that the user has actually
> >>>>>> built the executable for the target that corresponds to the
> >>>>>> host, so it doesn't work to try to default to that anyway.
> >>>>>
> >>>>> Agreed.  However, I don't see when exactly this message would be
> >>>>> triggered.  Cleber, on which use cases do you expect
> >>>>> pick_default_qemu_bin() to be called?
> >>>>>
> >>>>
> >>>> When a test is run ad-hoc.  You even suggested that tests could/should
> >>>> be executable.
> >>>>
> >>>>> In an ideal world, any testing runner/tool should be able to
> >>>>> automatically test all binaries by default.  Can Avocado help us
> >>>>> do that?  (If not, we could just do it inside a
> >>>>> ./tests/acceptance/run script).
> >>>>>
> >>>>
> >>>> Avocado can do that indeed.  But I'm afraid that's not the main issue.
> >>>> Think of the qemu-iotests: do we want a "check" command to run  all
> >>>> tests with all binaries?
> >>>
> >>> Good question.  That would be my first expectation, but I'm not
> >>> sure.
> >>>
> >>
> >> If it wasn't clear, I'm trying to define the basic behavior of *one
> >> test*.  I'm aware of a few different behaviors across tests in QEMU:
> > 
> > I think we have some confusion here: I'm not sure what you mean
> > when you say "one test".  Note that I'm not talking about the
> > test code architecture, but about the interface we provide for
> > running tests.
> > 
> >>
> >>  1) qemu-iotests: require "check" to run, will attempt to find/run with
> >> a "suitable" QEMU binary.
> >>
> >>  2) libqtest based: executables, in theory runnable by themselves, and
> >> will not attempt to find/run a "suitable" QEMU binary.  Those will
> >> print: "Environment variable QTEST_QEMU_BINARY required".
> >>
> >>  3) acceptance tests: require the Avocado test runner, will attempt to
> >> find/run with a "suitable" QEMU binary.
> >>
> >> So, I'm personally not aware of any test in QEMU which *by themselves*
> >> defaults to running on all (relevant) built targets (machine types?
> >> device types?).  Test selection (defining a test suite) and setting
> >> parameters is always done elsewhere (Makefile, check-block.sh,
> >> qemu-iotests-quick.sh, etc).
> >>
> >>> Pro: testing all binaries by default would cause less confusion
> >>> than picking a random QEMU binary.
> >>>
> >>
> >> IMO we have to differentiate between *in test* QEMU binary selection
> >> (some? none?) and other layers (Makefiles, scripts, etc).
> >>
> >>> Con: testing all binaries may be inconvenient for quickly
> >>> checking if a test case works.  (I'm not convinced this is a
> >>> problem.  If you don't want to test everything, you probably
> >>> already have a short target list in your ./configure line?)
> >>>
> >>
> >> Convenience is important, but I'm convinced this is a software layering
> >> problem.  I have the feeling we're trying to impose higher level
> >> (environment/build/check) definitions to the lower level (test) entities.
> > 
> > I think we're mixing user interface with code
> > layering/organization.
> > 
> > The code organization may ensure the QEMU binary selection is in
> > another layer.  That's fine.
> > 
> 
> OK.
> 
> > But the user interface we provide to running a single test should
> > be usable (and do what users expect).  That's where I think the
> > problem lies.  Maybe this UI problem could be addressed by
> > avocado, maybe it can be addressed by a wrapper script (see
> > comments below).
> > 
> > 
> 
> I absolutely agree with "running a single test should be usable (and do
> what users expect)".
> 
> >>
> >>> Pro: testing a single binary using uname() is already
> >>> implemented.
> >>>
> >>
> >> Right.  I'm not unfavorable to changing that behavior, and ERRORing
> >> tests when a binary is not given (similar to libqtest) is a simple
> >> change if we're to do it.  But I do find that usability drops considerably.
> >>
> >> And finally I don't think the "if a qemu binary is not explicitly given,
> >> let's try the matching host architecture" is confusing or hard to
> >> follow.  And, it's pretty well documented if you ask me:
> > 
> > I think it may cause confusion, and is inconsistent with all
> > other methods we recommend for running tests.
> > 
> 
> It's hard to argue against "it may cause confusion" when something is
> decided during runtime, so you clearly have a point.  But, given the
> behavior of the iotests which is exactly that, I don't consider it
> inconsistent with all other tests in QEMU.  As Peter said, it may not be
> a model to follow, though.

Yeah, we don't seem to have a consistent rule, here.

Anyway, maybe "run against all binaries" won't be an absolute
rule: maybe we'll have exceptions on some cases to keep the size
of test jobs under control.

iotests itself looks like a justifiable exception: if the full
test suite takes very long to run and it's testing mostly
arch-independent code, it could make sense to choose only one
QEMU binary for running those tests by default.


> 
> >>
> >> ---
> >> QEMU binary selection
> >> ~~~~~~~~~~~~~~~~~~~~~
> >>
> >> The QEMU binary used for the ``self.vm`` QEMUMachine instance will
> >> primarily depend on the value of the ``qemu_bin`` parameter.  If it's
> >> not explicitly set, its default value will be the result of a dynamic
> >> probe in the same source tree.  A suitable binary will be one that
> >> targets the architecture matching (the) host machine.
> >>
> >> Based on this description, test writers will usually rely on one of
> >> the following approaches:
> >>
> >> 1) Set ``qemu_bin``, and use the given binary
> >>
> >> 2) Do not set ``qemu_bin``, and use a QEMU binary named like
> >>    "${arch}-softmmu/qemu-system-${arch}", either in the current
> >>    working directory, or in the current source tree.
> >>
> >> The resulting ``qemu_bin`` value will be preserved in the
> >> ``avocado_qemu.Test`` as an attribute with the same name.
> > 
> > If we provide a good user interface for running single tests
> > against all binaries, users won't even care about `qemu_bin`, and
> > this would be just a low level details inside the avocado_qemu
> > code.
> > 
> > "This is documented" is good.  "This doesn't need to be
> > documented" would be awesome.
> > 
> > 
> 
> Agreed.
> 
> >> ---
> >>
> >>> Con: making `avocado run` automatically generate variants of a
> >>> test case may take some effort?
> >>>
> >>
> >> Well, it will take some effort, sure.  But my point do we want to
> >> *enforce* that?  I think that should be left to a "run" script or make
> >> rule like you suggested.  IMO, `avocado run a_single_test.py` shouldn't
> >> do more than just that.
> > 
> > What do you mean by "do just that"?
> 
> I mean "running a single test" (one test, one variant).  The test
> results would show a "RESULTS: PASS 1 | FAIL 0 | ... | CANCEL 0".

Got it.


> 
> > 
> > I would love if avocado could be smarter and
> > "avocado run [<test>]" automatically got test variant information
> > somewhere and run multiple variants.  But if this is not possible
> > today, a wrapper script would be good enough to me.
> > 
> 
> We're definitely on the same page, and, I believe this could be
> implemented with a new varianter plugin.  Then, doing:
> 
>  $ avocado run --varianter-qemu-targets-built <test>
> 
> Would give us N test executions, one per variant.  I kind of
> demonstrated that with the variants/arch.json file.
> 
> Now, nothing prevents us from having an Avocado configuration file that
> will make "--varianter-qemu-targets-built" a default option when running
> inside a QEMU build tree.  Then, I'd expect:
> 
>  $ avocado config
>  Config files read (in order):
>       /etc/avocado/avocado.conf
>       ...
>       /tmp/qemu-build/.avocado.conf
> 
> And "avocado run a_single_test.py" to produce to produce something like:
> 
> JOB ID     : 0fb835fb82d26627456c9f6af045858b20e1e5af
> JOB LOG    : job-results/job-2018-10-17T19.04-0fb835f/job.log
> VARIANTS   : QEMUBuiltTargets [x86_64-softmmu, ppc64-softmmu]
>  (1/2) : a_single_test.py-x86_64-softmmu PASS (0.03 s)
>  (2/2) : a_single_test.py-ppc64-softmmu PASS (0.03 s)
> RESULTS    : PASS 2 | ERROR 0 | FAIL 0 | SKIP 0 | WARN 0 | INTERRUPT 0 |
> CANCEL 0
> JOB TIME   : 0.19 s
> 
> Does this fits into your understanding of what we need?

Absolutely.  Thanks!

-- 
Eduardo