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From:   Daniel Latypov <dlatypov@google.com>
Date:   Thu, 14 Jul 2022 16:45:55 -0700
Message-ID: <CAGS_qxq5AAe0vB8N5Eq+WKKNBchEW++Cap2UDo=2hqGzjAekCg@mail.gmail.com>
Subject: Re: [PATCH 2/2] kcsan: test: Add a .kunitconfig to run KCSAN tests
To:     Marco Elver <elver@google.com>
Cc:     David Gow <davidgow@google.com>,
        Brendan Higgins <brendanhiggins@google.com>,
        Shuah Khan <skhan@linuxfoundation.org>,
        Dmitry Vyukov <dvyukov@google.com>,
        KUnit Development <kunit-dev@googlegroups.com>,
        kasan-dev <kasan-dev@googlegroups.com>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Thu, Jul 14, 2022 at 2:41 PM Marco Elver <elver@google.com> wrote:
>
> On Thu, 14 Jul 2022 at 22:23, Daniel Latypov <dlatypov@google.com> wrote:
> >
> > On Thu, May 19, 2022 at 6:24 AM Marco Elver <elver@google.com> wrote:
> > > I'd keep it simple for now, and remove both lines i.e. make non-strict
> > > the default. It's easy to just run with --kconfig_add
> > > CONFIG_KCSAN_STRICT=y, along with other variations. I know that
> > > rcutoruture uses KCSAN_STRICT=y by default, so it's already getting
> > > coverage there. ;-)
> >
> > David decided to drop the parent patch (the new QEMU config) now
> > --qemu_args was merged into the kunit tree.
> > Did we want a standalone v2 of this patch?
> >
> > Based on Marco's comments, we'd change:
> > * drop CONFIG_KCSAN_STRICT=y per this comment [1]
> > * drop CONFIG_KCSAN_WEAK_MEMORY per previous comments
> > Then for --qemu_args changes:
> > * add CONFIG_SMP=y explicitly to this file
> > * update the comment to show to include --qemu_args="-smp 8"
> >
> > Does this sound right?
>
> Yes, sounds good to me, and thanks for remembering this. I'd prefer a
> close-to-default config.
>
> > [1] Note: there's also patches in kunit now so you could do
> > --kconfig_add=CONFIG_KCSAN_STRICT=n to explicitly disable it. This
> > wasn't possible before. Does that change what we want for the default?
>
> I'd just have KCSAN_STRICT=n by default, and if desired it can be
> added per kconfig_add just the same way.

Ack.
So concretely, so then a final result like this?

$ cat kernel/kcsan/.kunitconfig
# Note that the KCSAN tests need to run on an SMP setup.
# Under kunit_tool, this can be done by using the x86_64-smp
# qemu-based architecture:
# ./tools/testing/kunit/kunit.py run --kunitconfig=kernel/kcsan
--arch=x86_64 --qemu_args='-smp 8'

CONFIG_KUNIT=y

CONFIG_DEBUG_KERNEL=y

CONFIG_KCSAN=y
CONFIG_KCSAN_KUNIT_TEST=y

# Need some level of concurrency to test a concurrency sanitizer.
CONFIG_SMP=y

# This prevents the test from timing out on many setups. Feel free to remove
# (or alter) this, in conjunction with setting a different test timeout with,
# for example, the --timeout kunit_tool option.
CONFIG_KCSAN_REPORT_ONCE_IN_MS=100