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Subject: Re: [RFC 0/3] kunit: add support to use modules
From:   Vitor Massaru Iha <vitor@massaru.org>
To:     David Gow <davidgow@google.com>
Cc:     KUnit Development <kunit-dev@googlegroups.com>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
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        Brendan Higgins <brendanhiggins@google.com>,
        Kees Cook <keescook@chromium.org>,
        Shuah Khan <skhan@linuxfoundation.org>,
        linux-kernel-mentees@lists.linuxfoundation.org
Date:   Thu, 16 Jul 2020 13:21:17 -0300
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On Wed, 2020-07-15 at 11:47 +0800, David Gow wrote:
> On Wed, Jul 15, 2020 at 11:11 AM Vitor Massaru Iha <vitor@massaru.org
> > wrote:
> > Currently, KUnit does not allow the use of tests as a module.
> > This prevents the implementation of tests that require userspace.
> 
> If this is what I think it is, thanks! I'll hopefully get a chance to
> play with it over the next few days.
> 
> Can we clarify what this means: the current description is a little
> misleading, as KUnit tests can already be built and run as modules,
> and "tests that require userspace" is a bit broad.
> 
> As I understand it, this patchset does three things:
> - Let kunit_tool install modules to a root filesystem and boot UML
> with that filesystem.
> - Have tests inherit the mm of the process that started them, which
> (if the test is in a module), provides a user-space memory context so
> that copy_{from,to}_user() works.
> - Port the test_user_copy.c tests to KUnit, using this new feature.
> 
> A few comments from my quick glance over it:
> - The rootfs support is useful: I'm curious how it'll interact with
> non-UML architectures in [1]. It'd be nice for this to be extensible
> and to not explicitly state UML where possible.

Hm, I didn't think about other architectures. Which ones are you
thinking ?

> - The inheriting of the mm stuff still means that
> copy_{from,to}_user() will only work if loaded as a module. This
> really needs to be documented. (Ideally, we'd find a way of having
> this work even for built-in tests, but I don't have any real ideas as
> to how that could be done).

Sure, I'll write the documentation.

> - It'd be nice to split the test_user_copy.c test port into a
> separate
> commit. In fact, it may make sense to also split the kunit_tool
> changes and the mm changes into separate series, as they're both
> quite
> useful independently.
> 

I'll do it.

Thanks for the review.