[PATCH] kunit: fix Kconfig for build-in tests USB4 and Nitro Enclaves

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Nico Pache

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Aug 10, 2022, 7:41:11 PMAug 10
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Both the USB4 and Nitro Enclaves KUNIT tests are now able to be compiled
if KUNIT is compiled as a module. This leads to issues if KUNIT is being
packaged separately from the core kernel and when KUNIT is run baremetal
without the required driver compiled into the kernel.

Fixes: 635dcd16844b ("thunderbolt: test: Use kunit_test_suite() macro")
Fixes: fe5be808fa6c ("nitro_enclaves: test: Use kunit_test_suite() macro")
Signed-off-by: Nico Pache <npa...@redhat.com>
---
drivers/thunderbolt/Kconfig | 3 +--
drivers/virt/nitro_enclaves/Kconfig | 2 +-
2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/thunderbolt/Kconfig b/drivers/thunderbolt/Kconfig
index e76a6c173637..f12d0a3ee3e2 100644
--- a/drivers/thunderbolt/Kconfig
+++ b/drivers/thunderbolt/Kconfig
@@ -29,8 +29,7 @@ config USB4_DEBUGFS_WRITE

config USB4_KUNIT_TEST
bool "KUnit tests" if !KUNIT_ALL_TESTS
- depends on (USB4=m || KUNIT=y)
- depends on KUNIT
+ depends on USB4 && KUNIT=y
default KUNIT_ALL_TESTS

config USB4_DMA_TEST
diff --git a/drivers/virt/nitro_enclaves/Kconfig b/drivers/virt/nitro_enclaves/Kconfig
index ce91add81401..dc4d25c26256 100644
--- a/drivers/virt/nitro_enclaves/Kconfig
+++ b/drivers/virt/nitro_enclaves/Kconfig
@@ -17,7 +17,7 @@ config NITRO_ENCLAVES

config NITRO_ENCLAVES_MISC_DEV_TEST
bool "Tests for the misc device functionality of the Nitro Enclaves" if !KUNIT_ALL_TESTS
- depends on NITRO_ENCLAVES && KUNIT
+ depends on NITRO_ENCLAVES && KUNIT=y
default KUNIT_ALL_TESTS
help
Enable KUnit tests for the misc device functionality of the Nitro
--
2.36.1

David Gow

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Aug 10, 2022, 8:20:22 PMAug 10
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On Thu, Aug 11, 2022 at 7:41 AM Nico Pache <npa...@redhat.com> wrote:
>
> Both the USB4 and Nitro Enclaves KUNIT tests are now able to be compiled
> if KUNIT is compiled as a module. This leads to issues if KUNIT is being
> packaged separately from the core kernel and when KUNIT is run baremetal
> without the required driver compiled into the kernel.
>
> Fixes: 635dcd16844b ("thunderbolt: test: Use kunit_test_suite() macro")
> Fixes: fe5be808fa6c ("nitro_enclaves: test: Use kunit_test_suite() macro")
> Signed-off-by: Nico Pache <npa...@redhat.com>
> ---

Hmm... I'm not quite sure I understand the case that's broken here. Is it:
- KUnit is built as a module (CONFIG_KUNIT=m)
- USB4/nitro_enclaves are also built as modules, with the test enabled.
- The kunit module is not available at runtime, so neither driver
module can load (due to missing kunit dependencies)

If so, that's not a case (i.e., the kunit.ko module being unavailable
if it was built) we've tried to support thus far. I guess a de-facto
rule for supporting it would be to depend on KUNIT=y for any KUnit
tests which are built into the same module as the driver they're
testing.

Alternatively, maybe we could do some horrible hacks to compile stub
versions of various KUnit assertion symbols in unconditionally, which
forward to the real ones if KUnit is available.

(Personally, I'd love it if we could get rid of CONFIG_KUNIT=m
altogether, and it's actually broken right at the moment[1]. There are
still some cases (unloading / reloading KUnit with different filter
options) which require it, though.)

Cheers,
-- David

[1]: https://patchwork.kernel.org/project/linux-kselftest/patch/20220713005221.1...@google.com/

> drivers/thunderbolt/Kconfig | 3 +--
> drivers/virt/nitro_enclaves/Kconfig | 2 +-
> 2 files changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/thunderbolt/Kconfig b/drivers/thunderbolt/Kconfig
> index e76a6c173637..f12d0a3ee3e2 100644
> --- a/drivers/thunderbolt/Kconfig
> +++ b/drivers/thunderbolt/Kconfig
> @@ -29,8 +29,7 @@ config USB4_DEBUGFS_WRITE
>
> config USB4_KUNIT_TEST
> bool "KUnit tests" if !KUNIT_ALL_TESTS
> - depends on (USB4=m || KUNIT=y)
> - depends on KUNIT
> + depends on USB4 && KUNIT=y

This can probably just:
depends on KUNIT=y

Nico Pache

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Aug 11, 2022, 8:44:00 AMAug 11
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On Wed, Aug 10, 2022 at 8:20 PM David Gow <davi...@google.com> wrote:
>
> On Thu, Aug 11, 2022 at 7:41 AM Nico Pache <npa...@redhat.com> wrote:
> >
> > Both the USB4 and Nitro Enclaves KUNIT tests are now able to be compiled
> > if KUNIT is compiled as a module. This leads to issues if KUNIT is being
> > packaged separately from the core kernel and when KUNIT is run baremetal
> > without the required driver compiled into the kernel.
> >
> > Fixes: 635dcd16844b ("thunderbolt: test: Use kunit_test_suite() macro")
> > Fixes: fe5be808fa6c ("nitro_enclaves: test: Use kunit_test_suite() macro")
> > Signed-off-by: Nico Pache <npa...@redhat.com>
> > ---
>
> Hmm... I'm not quite sure I understand the case that's broken here. Is it:
> - KUnit is built as a module (CONFIG_KUNIT=m)
> - USB4/nitro_enclaves are also built as modules, with the test enabled.
> - The kunit module is not available at runtime, so neither driver
> module can load (due to missing kunit dependencies)
Exactly, except the issue is also when the USB/NE=y not just when they
are modules. This is currently creating an issue with our build system
during the depmod stage and has been preventing us from generating
Fedora builds.
>
> If so, that's not a case (i.e., the kunit.ko module being unavailable
> if it was built) we've tried to support thus far. I guess a de-facto
> rule for supporting it would be to depend on KUNIT=y for any KUnit
> tests which are built into the same module as the driver they're
> testing.
Yeah, although it's not been a case you've been trying to support, it
has been working so far :) This has been the case (built-in tests
utilizing 'depends on KUNIT=y') since we began supporting KUNIT in our
testing infrastructure and it would be nice to keep that as a de-facto
rule :)
>
> Alternatively, maybe we could do some horrible hacks to compile stub
> versions of various KUnit assertion symbols in unconditionally, which
> forward to the real ones if KUnit is available.
>
> (Personally, I'd love it if we could get rid of CONFIG_KUNIT=m
> altogether, and it's actually broken right at the moment[1]. There are
> still some cases (unloading / reloading KUnit with different filter
> options) which require it, though.)
Personally I'd hate to see KUNIT=m go as that is how we have been able
to support running Kunit tests so far.

A little background on how we utilize Kunit. We build with KUNIT=m and
KUNIT_ALL_TESTS=m and run the tests baremetal.
Our build system creates 3 packages (kernel, kernel-modules, and
kernel-modules-internal), this allows us to ship the kernel and its
modules, while also isolating packages that we dont want to ship
outside of QE and developers. We then have our own infrastructure in
place to run and collect the output of these tests in our pipelined
environments. We dont utilize UML because we dont support that feature
in RHEL.

Fedora uses this same methodology for running KUNIT, so we are
frequently running kunit on an 'upstream' variant.

I'm not sure how many organizations are supporting continuous KUNIT
testing, or how they are achieving it, but dropping module support
would prevent us from doing the CI testing we have in place.

Cheers!
-- Nico

David Gow

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Aug 12, 2022, 2:43:47 AMAug 12
to Nico Pache, Joe Fradley, KUnit Development, Linux Kernel Mailing List, USB list, Shuah Khan, Daniel Latypov, Brendan Higgins, alc...@amazon.com, le...@amazon.com, Andra Paraschiv, Yehez...@gmail.com, Mika Westerberg, michae...@intel.com, andreas...@gmail.com
(+joefr...@google.com to comment on what Android is doing here)

On Thu, Aug 11, 2022 at 8:44 PM Nico Pache <npa...@redhat.com> wrote:
>
> On Wed, Aug 10, 2022 at 8:20 PM David Gow <davi...@google.com> wrote:
> >
> > On Thu, Aug 11, 2022 at 7:41 AM Nico Pache <npa...@redhat.com> wrote:
> > >
> > > Both the USB4 and Nitro Enclaves KUNIT tests are now able to be compiled
> > > if KUNIT is compiled as a module. This leads to issues if KUNIT is being
> > > packaged separately from the core kernel and when KUNIT is run baremetal
> > > without the required driver compiled into the kernel.
> > >
> > > Fixes: 635dcd16844b ("thunderbolt: test: Use kunit_test_suite() macro")
> > > Fixes: fe5be808fa6c ("nitro_enclaves: test: Use kunit_test_suite() macro")
> > > Signed-off-by: Nico Pache <npa...@redhat.com>
> > > ---
> >
> > Hmm... I'm not quite sure I understand the case that's broken here. Is it:
> > - KUnit is built as a module (CONFIG_KUNIT=m)
> > - USB4/nitro_enclaves are also built as modules, with the test enabled.
> > - The kunit module is not available at runtime, so neither driver
> > module can load (due to missing kunit dependencies)
> Exactly, except the issue is also when the USB/NE=y not just when they
> are modules. This is currently creating an issue with our build system
> during the depmod stage and has been preventing us from generating
> Fedora builds.
.
Yeah: there's a nasty tradeoff here in that having these depend on
KUNIT=y does (obviously) mean that it's not possible to run these
tests with KUNIT=m. I'd agree that being able to ruin some tests is
better than none, but there are quite a lot of tests which are doing
the same sort of tricks as USB4/nitro_enclaves to embed tests in the
same module as the code being tested. In particular, I think apparmor
is doing something similar, and the incoming AMDGPU tests also build
all of the tests into amdgpu.ko. If we require KUNIT=y for these,
we're leaving a lot of tests on the table for KUNIT=m cases, which
would otherwise work.

The ideal solution would be to split the tests for these systems out
into their own separate modules, but that's often quite tricky due to
the sheer number of otherwise internal symbols which need exporting.

> >
> > If so, that's not a case (i.e., the kunit.ko module being unavailable
> > if it was built) we've tried to support thus far. I guess a de-facto
> > rule for supporting it would be to depend on KUNIT=y for any KUnit
> > tests which are built into the same module as the driver they're
> > testing.
> Yeah, although it's not been a case you've been trying to support, it
> has been working so far :) This has been the case (built-in tests
> utilizing 'depends on KUNIT=y') since we began supporting KUNIT in our
> testing infrastructure and it would be nice to keep that as a de-facto
> rule :)

Okay: let's try to stick with that for now, then (unless there are any
objections from the people working on those particular tests), and
look to either reinstate it if we find a better way of dealing with
the missing/disabled kunit.ko case, or the tests can be split into a
separate module. Personally, I don't expect we'll get either of those
working in the short-term, but it's definitely a problem we'll have to
confront more eventually.

In the meantime, I think the KUnit position on this will be to note
this as a consequence of building KUnit tests into bigger modules, and
leave the final decision up to the maintainers of those
subsystems/tests. This may result in there being some tests you have
to explicitly disable (rather than being able to use KUNIT_ALL_TESTS)
if an important module decides that they really want their tests to
run when KUNIT=m (which may not happen, we'll see...)
Fair enough -- we definitely won't get rid of it unless there's a
replacement which works as well if not better.

The reason it's tempting to get rid of KUNIT=m is simply that there's
a chunk of KUnit code which needs to be built-in, even if the rest of
it is in a module. So a kernel with KUNIT=m still has a fair bit of
the overhead of KUNIT=y, and this is likely to get more significant as
more such features land (e.g., static stubbing:
https://lore.kernel.org/lkml/20220318021314.3...@google.com/
).

Traditionally, our expectation has been that a separate, KUnit-enabled
kernel config / build makes sense, as that allows the
release/production build to run without any testing-related overheads
at all. That being said, I know Android are looking to enable KUnit in
all GKI builds, and to implement a separate kunit.enable option to
effectively "disable" it at runtime. This doesn't remove all of the
overhead, but does allow KUnit to always be present without the risk
of compromising the integrity of the running kernel by running tests
in production.

Regardless of whether any of those seem interesting to you, we won't
be getting rid of KUNIT=m in the short-term (and definitely will be
supporting individual test modules, even if we later want to have the
core executor built-in).

One other note is that KUNIT=m is actually broken right at the moment:
the fix is here:
https://patchwork.kernel.org/project/linux-kselftest/patch/20220713005221.1...@google.com/

Cheers,
-- David

David Gow

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Aug 12, 2022, 2:47:48 AMAug 12
to Nico Pache, KUnit Development, Linux Kernel Mailing List, USB list, Shuah Khan, Daniel Latypov, Brendan Higgins, alc...@amazon.com, le...@amazon.com, Andra Paraschiv, Yehez...@gmail.com, Mika Westerberg, michae...@intel.com, andreas...@gmail.com
On Thu, Aug 11, 2022 at 7:41 AM Nico Pache <npa...@redhat.com> wrote:
>
> Both the USB4 and Nitro Enclaves KUNIT tests are now able to be compiled
> if KUNIT is compiled as a module. This leads to issues if KUNIT is being
> packaged separately from the core kernel and when KUNIT is run baremetal
> without the required driver compiled into the kernel.
>
> Fixes: 635dcd16844b ("thunderbolt: test: Use kunit_test_suite() macro")
> Fixes: fe5be808fa6c ("nitro_enclaves: test: Use kunit_test_suite() macro")
> Signed-off-by: Nico Pache <npa...@redhat.com>
> ---

This is okay by me, though it's worth noting that this will stop these
tests from building when CONFIG_KUNIT=m, so that the modules being
tested will still load when CONFIG_KUNIT=m was enabled, but the
kunit.ko file is missing.

So if you're relying on being able to run these tests with
CONFIG_KUNIT=m, you'll want to NACK this one.

There's one comment below, but otherwise (assuming the USB4 and
nitro_enclaves folks are okay with this tradeoff):
Reviewed-by: David Gow <davi...@google.com>

Cheers,
-- David

> drivers/thunderbolt/Kconfig | 3 +--
> drivers/virt/nitro_enclaves/Kconfig | 2 +-
> 2 files changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/thunderbolt/Kconfig b/drivers/thunderbolt/Kconfig
> index e76a6c173637..f12d0a3ee3e2 100644
> --- a/drivers/thunderbolt/Kconfig
> +++ b/drivers/thunderbolt/Kconfig
> @@ -29,8 +29,7 @@ config USB4_DEBUGFS_WRITE
>
> config USB4_KUNIT_TEST
> bool "KUnit tests" if !KUNIT_ALL_TESTS
> - depends on (USB4=m || KUNIT=y)
> - depends on KUNIT
> + depends on USB4 && KUNIT=y

"USB4 &&" shouldn't be necessary here: this opption is already under
USB4, IIRC...

Joe Fradley

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Aug 12, 2022, 12:15:47 PMAug 12
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Like David mentioned, internally for GKI we have KUNIT=y with running
built-in tests permanently disabled and only allowing module test
execution if a kernel command line option (kunit.enable) is set. I
hope to have an upstream patch of this for review soon. If you're
willing to have the extra KUnit overhead in your production build,
this could be an option for you as well.

Nico Pache

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Aug 13, 2022, 8:04:17 AMAug 13
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I have already started trying to separate out all the built-in tests.
There are a few which may have to stay as built-in if I can't find a
viable solution, but expect a patch-set doing just this soon :)

> > >
> > > If so, that's not a case (i.e., the kunit.ko module being unavailable
> > > if it was built) we've tried to support thus far. I guess a de-facto
> > > rule for supporting it would be to depend on KUNIT=y for any KUnit
> > > tests which are built into the same module as the driver they're
> > > testing.
> > Yeah, although it's not been a case you've been trying to support, it
> > has been working so far :) This has been the case (built-in tests
> > utilizing 'depends on KUNIT=y') since we began supporting KUNIT in our
> > testing infrastructure and it would be nice to keep that as a de-facto
> > rule :)
>
> Okay: let's try to stick with that for now, then (unless there are any
> objections from the people working on those particular tests), and
> look to either reinstate it if we find a better way of dealing with
> the missing/disabled kunit.ko case, or the tests can be split into a
> separate module. Personally, I don't expect we'll get either of those
> working in the short-term, but it's definitely a problem we'll have to
> confront more eventually.
>
> In the meantime, I think the KUnit position on this will be to note
> this as a consequence of building KUnit tests into bigger modules, and
> leave the final decision up to the maintainers of those
> subsystems/tests. This may result in there being some tests you have
> to explicitly disable (rather than being able to use KUNIT_ALL_TESTS)
> if an important module decides that they really want their tests to
> run when KUNIT=m (which may not happen, we'll see...)
Yep, explicitly disabling them is also an option for us, but I
submitted this patchset because I noticed a change in the pattern for
built-in tests (depends on KUNIT=y). So if people object to some tests
not having kunit module support, we do have the ability to work around
it.

Thanks for your review!

Cheers,
-- Nico

Nico Pache

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Aug 13, 2022, 8:40:47 AMAug 13
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Sweet :) I look forward to seeing that! That may be a viable option
for our approach too.

Cheers,
-- Nico

Paraschiv, Andra-Irina

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Aug 15, 2022, 1:45:23 AMAug 15
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For the Nitro Enclaves part:

Reviewed-by: Andra Paraschiv <andr...@amazon.com>

Thank you.

Andra

> --
> 2.36.1
>

Amazon Development Center (Romania) S.R.L. registered office: 27A Sf. Lazar Street, UBC5, floor 2, Iasi, Iasi County, 700045, Romania. Registered in Romania. Registration number J22/2621/2005.

Brendan Higgins

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Aug 29, 2022, 6:50:04 PMAug 29
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On Wed, Aug 10, 2022 at 4:41 PM Nico Pache <npa...@redhat.com> wrote:
>
> Both the USB4 and Nitro Enclaves KUNIT tests are now able to be compiled
> if KUNIT is compiled as a module. This leads to issues if KUNIT is being
> packaged separately from the core kernel and when KUNIT is run baremetal
> without the required driver compiled into the kernel.
>
> Fixes: 635dcd16844b ("thunderbolt: test: Use kunit_test_suite() macro")
> Fixes: fe5be808fa6c ("nitro_enclaves: test: Use kunit_test_suite() macro")
> Signed-off-by: Nico Pache <npa...@redhat.com>

Acked-by: Brendan Higgins <brendan...@google.com>
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