Re: [PATCH 14/16] tests: add QEMU_TEST_IO_SKIP for skipping I/O tests

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, May 12, 2026 at 10:53:05AM -0700, Pierrick Bouvier wrote:
> On 5/12/2026 10:24 AM, Daniel P. Berrangé wrote:
> > On Tue, May 12, 2026 at 10:09:53AM -0700, Pierrick Bouvier wrote:
> >> On 5/12/2026 9:53 AM, Daniel P. Berrangé wrote:
> >>> On Tue, May 12, 2026 at 09:47:12AM -0700, Pierrick Bouvier wrote:
> >>>> On 5/12/2026 9:36 AM, Daniel P. Berrangé wrote:
> >>>>> On Tue, May 12, 2026 at 09:19:45AM -0700, Pierrick Bouvier wrote:
> >>>>>> On 5/12/2026 9:06 AM, Daniel P. Berrangé wrote:
> >>>>>>> On Tue, May 12, 2026 at 08:56:54AM -0700, Pierrick Bouvier wrote:
> >>>>>>>> On 4/24/2026 8:42 AM, Daniel P. Berrangé wrote:
> >>>>>>>>> The nature of block I/O tests is such that there can be unexpected false
> >>>>>>>>> positive failures in certain scenarios that have not been encountered
> >>>>>>>>> before, and sometimes non-deterministic failures that are hard to
> >>>>>>>>> reproduce.
> >>>>>>>>>
> >>>>>>>>> Before enabling the I/O tests as gating jobs in CI, there needs to be a
> >>>>>>>>> mechanism to dynamically mark tests as skipped, without having to commit
> >>>>>>>>> code changes.
> >>>>>>>>>
> >>>>>>>>> This introduces the QEMU_TEST_IO_SKIP environment variable that is set
> >>>>>>>>> to a list of FORMAT-OR-PROTOCOL:NAME pairs. The intent is that this
> >>>>>>>>> variable can be set as a GitLab CI pipeline variable to temporarily
> >>>>>>>>> disable a test while problems are being debugged.
> >>>>>>>>>
> >>>>>>>>> Reviewed-by: Thomas Huth <thuth@redhat.com>
> >>>>>>>>> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> >>>>>>>>> ---
> >>>>>>>>>  docs/devel/testing/main.rst      |  7 +++++++
> >>>>>>>>>  tests/qemu-iotests/testrunner.py | 16 ++++++++++++++++
> >>>>>>>>>  2 files changed, 23 insertions(+)
> >>>>>>>>>
> >>>>>>>>> diff --git a/docs/devel/testing/main.rst b/docs/devel/testing/main.rst
> >>>>>>>>> index 797111009a..f779a64415 100644
> >>>>>>>>> --- a/docs/devel/testing/main.rst
> >>>>>>>>> +++ b/docs/devel/testing/main.rst
> >>>>>>>>> @@ -284,6 +284,13 @@ that are specific to certain cache mode.
> >>>>>>>>>  More options are supported by the ``./check`` script, run ``./check -h`` for
> >>>>>>>>>  help.
> >>>>>>>>>  
> >>>>>>>>> +If a test program is known to be broken, it can be disabled by setting
> >>>>>>>>> +the ``QEMU_TEST_IO_SKIP`` environment variable with a list of tests to
> >>>>>>>>> +be skipped. The values are of the form FORMAT-OR-PROTOCOL:NAME, the
> >>>>>>>>> +leading component can be omitted to skip the test for all formats and
> >>>>>>>>> +protocols. For example ``export QEMU_TEST_IO_SKIP="luks:149 185 iov-padding``
> >>>>>>>>> +will skip ``149`` for LUKS only, and ``185`` and ``iov-padding`` for all.
> >>>>>>>>> +
> >>>>>>>>>  Writing a new test case
> >>>>>>>>>  ~~~~~~~~~~~~~~~~~~~~~~~
> >>>>>>>>>  
> >>>>>>>>> diff --git a/tests/qemu-iotests/testrunner.py b/tests/qemu-iotests/testrunner.py
> >>>>>>>>> index dbe2dddc32..ecb5d4529f 100644
> >>>>>>>>> --- a/tests/qemu-iotests/testrunner.py
> >>>>>>>>> +++ b/tests/qemu-iotests/testrunner.py
> >>>>>>>>> @@ -145,6 +145,18 @@ def __init__(self, env: TestEnv, tap: bool = False,
> >>>>>>>>>  
> >>>>>>>>>          self._stack: contextlib.ExitStack
> >>>>>>>>>  
> >>>>>>>>> +        self.skip = {}
> >>>>>>>>> +        for rule in os.environ.get("QEMU_TEST_IO_SKIP", "").split(" "):
> >>>>>>>>> +            rule = rule.strip()
> >>>>>>>>> +            if rule == "":
> >>>>>>>>> +                continue
> >>>>>>>>> +            if ":" in rule:
> >>>>>>>>> +                fmt, name = rule.split(":")
> >>>>>>>>> +                if fmt in ("", env.imgfmt, env.imgproto):
> >>>>>>>>> +                    self.skip[name] = True
> >>>>>>>>> +            else:
> >>>>>>>>> +                self.skip[rule] = True
> >>>>>>>>> +
> >>>>>>>>>      def __enter__(self) -> 'TestRunner':
> >>>>>>>>>          self._stack = contextlib.ExitStack()
> >>>>>>>>>          self._stack.enter_context(self.env)
> >>>>>>>>> @@ -251,6 +263,10 @@ def do_run_test(self, test: str) -> TestResult:
> >>>>>>>>>                                description='No qualified output '
> >>>>>>>>>                                            f'(expected {f_reference})')
> >>>>>>>>>  
> >>>>>>>>> +        if f_test.name in self.skip:
> >>>>>>>>> +            return TestResult(status='not run',
> >>>>>>>>> +                              description='Listed in QEMU_TEST_IO_SKIP')
> >>>>>>>>> +
> >>>>>>>>>          args = [str(f_test.resolve())]
> >>>>>>>>>          env = self.env.prepare_subprocess(args)
> >>>>>>>>>  
> >>>>>>>>
> >>>>>>>> Why not simply remove the broken tests, and create issues to add them
> >>>>>>>> again in the future?
> >>>>>>>
> >>>>>>> In theory that's what our policy today is, but in practice it is
> >>>>>>> too much of a burden on the release co-ordinator, to expect them
> >>>>>>> to create such a patch themselves, or wait on a subsys maintainer
> >>>>>>> todo it for them.
> >>>>>>>
> >>>>>>> They end up just ignoring brokenness in CI which is a bad practice,
> >>>>>>> and will prevent us ever making CI truely gating or switching to
> >>>>>>> using MRs for pull requests. This gives us a super-fast way to skip
> >>>>>>> flaky tests, while the subsystem maintainers figure out the right
> >>>>>>> permanent answer.
> >>>>>>>
> >>>>>>
> >>>>>> I disagree on this one, merging a single patch doing a git rm, and a git
> >>>>>> revert later is not more expensive than merging a variable modifying a
> >>>>>> variable in a yaml file.
> >>>>>
> >>>>> Any code changes like that need to be sent back to the subsystem
> >>>>> maintainer to be acked. IMHO the release manager should not be
> >>>>> unilaterally deleting tests without peer review.  So that's
> >>>>> got a non-negligible turn around time, during which CI is broken.
> >>>>>
> >>>>
> >>>> I accept the argument, but it seems like a workaround for a human
> >>>> process, more than a proper solution to the problem.
> >>>>
> >>>> It would be better to have a proper policy for build/test fixes, instead
> >>>> of implementing local overrides to this.
> >>>>
> >>>>> Setting an env variable to skip a problematic test is something
> >>>>> reasonable to do with zero oversight.
> >>>>>
> >>>>>> The issue with this approach is that people running tests locally will
> >>>>>> not see which tests are skipped, and will see false positives. So you
> >>>>>> just keep CI green, but not the test base itself.
> >>>>>
> >>>>> I would still expect the release manager to file a bug about any
> >>>>> flaky test they disable via the env var, and the subsystem maintainer
> >>>>> should still be fixing it or disabling it such that tests won't fail
> >>>>> more broadly, or deciding to remove it if terminally broken.
> >>>>>
> >>>>> We're just decoupling the process so that there is an immediate
> >>>>> workaround possible. It can also be used by people working in
> >>>>> their forks - often I've been testing stuff in my fork, but
> >>>>> see spurious failures because git master has a non-deterministic
> >>>>> test failure merged. I would like to easily skip those in my fork
> >>>>> too, without adding extra commits to me working branches, as that
> >>>>> would require the same commit to be duped into several in-progress
> >>>>> branches, vs setting the env var once.
> >>>>>
> >>>>>> The risk I see is that some tests will stay forever in this skip
> >>>>>> variable, so it will be dead code for CI, but still alive and failing
> >>>>>> for people running tests manually who hit the regression.
> >>>>>
> >>>>> Again, there should be a bug filed for any flaky test. Anyone can
> >>>>> do this, if they see it locally or in their fork CI, or in staging
> >>>>> CI. If no one can see an obvious fix, then anyone can also propose
> >>>>> to disable the test.
> >>>>>
> >>>>>> If you still want an alternative to removing test, implementing a
> >>>>>> skip_list in tests/qemu-iotests/meson.build is better than an env var
> >>>>>> IMHO, and achieves the exact same effect, for CI and for users.
> >>>>>>
> >>>>>> What do you think?
> >>>>>
> >>>>> IMHO there needs to be a way to skip flaky tests which does not
> >>>>> require code changes as the only available option. Code changes
> >>>>> are the permanent fix, env var is the immediate workaround.
> >>>>>
> >>>>
> >>>> I'm not sure all this answers to my question about How to ensure users
> >>>> who run tests and the CI both see the same skip list.
> >>>>
> >>>> I don't mind having an env var, a black list in meson or any other
> >>>> solution, but having different results on a dev machine and in CI is not
> >>>> a good design. So whatever the solution is, the CI yaml file is not the
> >>>> proper place to store this information.
> >>>
> >>> AFAICT the test 185 that is being skipped in the CI yaml file only
> >>> fails when run under gitlab. I've never seen a failure running it
> >>> locally.
> >>>
> >>> If it failed locally too, then I'd agree that it should not be
> >>> skipped in the CI yaml, but universally skipped in all scenarios.
> >>>
> >>
> >> If I get all this correctly, we add a generic mechanic to be able to
> >> gate CI with block tests just because there is a single test failing
> >> with a single driver. Is that the right approach?
> > 
> > The env variable is the generic mechanism.
> > 
> > The yaml file exclusion for 185 is the special case, but we get
> > that basically for free with the former.
> > 
> >> In the future, do we expect to merge code breaking tests?
> > 
> > Yes. We will certainly merge more non-deterministic tests. We've seen
> > this over & over again. Something passes CI initially but after a
> > number of CI pipelines turns out to be flaky
> >
> 
> Then we can mark them as flaky in tests/qemu-iotests/meson.build.

That is a long term solution. It does not address the immediate
time critical goal to have the ability to fix a broken CI pipeline
immediately by skipping the test without waiting for code changes.

> It seems like you ignore the point that there is a problem between
> setting something in CI only vs making something that works for all
> users. I'm not against an env var, I just don't see how it answers this
> need.

Again, I'm not saying that we fix this only for CI. The env var is
to allow broken jobs to be immediately skipped, while waiting for
code changes to permanently skipped/fix the tests. The latter
addresses it for every scenario.

With regards,
Daniel
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