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 11:52:45AM -0700, Pierrick Bouvier wrote:
> On 5/12/2026 11:46 AM, Daniel P. Berrangé wrote:
> > 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.
> >
> 
> I might have missed where we have a default value for this env var, out
> of yaml file, that makes it apply the exact same set of skip tests for
> CI, and for users running tests manually.
> 
> Where is this default applied for both CI and users?
>
> I understand it's not needed for test 185 which fails only in GitLab,
> but as you mentioned, we'll probably have non deterministic tests in the
> future, so we need to consider this.

I was considering any change in meson.build to permanently skip a
test would be independent of the env var handling, and outside the
scope of this series since there's no need for it here.


With regards,
Daniel
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