Date:   Fri, 3 Mar 2023 11:56:26 +0100 (GMT+01:00)
From:   Matthieu Baerts <matthieu.baerts@tessares.net>
To:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     Naresh Kamboju <naresh.kamboju@linaro.org>,
        Paolo Abeni <pabeni@redhat.com>, stable@vger.kernel.org,
        patches@lists.linux.dev, linux-kernel@vger.kernel.org,
        torvalds@linux-foundation.org, akpm@linux-foundation.org,
        linux@roeck-us.net, shuah@kernel.org, patches@kernelci.org,
        lkft-triage@lists.linaro.org, pavel@denx.de, jonathanh@nvidia.com,
        f.fainelli@gmail.com, sudipm.mukherjee@gmail.com,
        srw@sladewatkins.net, rwarsow@gmx.de, mptcp@lists.linux.dev,
        Florian Westphal <fw@strlen.de>,
        Mat Martineau <mathew.j.martineau@linux.intel.com>,
        Anders Roxell <anders.roxell@linaro.org>
Message-ID: <b4cb0542-df0c-48ae-b791-8c0a601f6ec0@tessares.net>
In-Reply-To: <ZAHLYvOPEYghRcJ1@kroah.com>
References: <20230301180657.003689969@linuxfoundation.org> <CA+G9fYtDGpgT4dckXD-y-N92nqUxuvue_7AtDdBcHrbOMsDZLg@mail.gmail.com> <ZAB6pP3MNy152f+7@kroah.com> <CA+G9fYsHbQyQFp+vMnmFKDSQxrmj-VKsexWq-aayxgrY+0O7KQ@mail.gmail.com> <CA+G9fYsn+AhWTFA+ZJmfFsM71WGLPOFemZp_vhFMMLUcgcAXKg@mail.gmail.com> <9586d0f99e27483b600d8eb3b5c6635b50905d82.camel@redhat.com> <CA+G9fYuLQEfeTjx52NxbXV5914YJQ2tVd8k4SJjrAryujPjnqA@mail.gmail.com> <ZAG8dla274kYfxoK@kroah.com> <3d92e773-896c-43c3-94ae-cb7851213c55@tessares.net> <ZAHLYvOPEYghRcJ1@kroah.com>
Subject: Re: [PATCH 6.1 00/42] 6.1.15-rc1 review
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Hi Greg,

3 Mar 2023 11:26:46 Greg Kroah-Hartman <gregkh@linuxfoundation.org>:

> On Fri, Mar 03, 2023 at 10:47:33AM +0100, Matthieu Baerts wrote:
>> Hi Greg, Naresh, Paolo,
>>
>> Thank you for the new version and for having reported the issue and runn=
ing MPTCP selftests!
>>
>> 3 Mar 2023 10:23:06 Greg Kroah-Hartman <gregkh@linuxfoundation.org>:
>>
>>> On Fri, Mar 03, 2023 at 02:34:05PM +0530, Naresh Kamboju wrote:
>>>> On Fri, 3 Mar 2023 at 13:34, Paolo Abeni <pabeni@redhat.com> wrote:
>>>>>
>>>>> Hello,
>>>>>
>>>>> On Fri, 2023-03-03 at 01:32 +0530, Naresh Kamboju wrote:
>>>>>> =E2=80=A6
>>>>>
>>>>> I read the above as you are running self-tests from 6.2.1 on top of a=
n
>>>>> older (6.1) kernel. Is that correct?
>>>>
>>>> correct.
>>>>
>>>>> If so failures are expected;
>>>
>>> Shouldn't the test be able to know that "new features" are not present
>>> and properly skip the test for when that happens?=C2=A0 Otherwise this =
feels
>>> like a problem going forward as no one will know if this feature can be
>>> used or not (assuming it is a new feature and not just a functional
>>> change.)
>>
>> All MPTCP selftests are designed to run on the same kernel version
>> they are attached to. This allows us to do more checks knowing they
>> are not supposed to fail on newer kernel versions and not being
>> skipped if there is an error when trying to use the new feature. If
>> there are fixes, we make sure the stable team is Cc'ed. If there are
>> API changes, it would be visible because we would need to adapt
>> existing selftests.
>
> "Features" are not usually limited to specific kernel versions (think
> about the mess that "enterprise" kernels create by backports).=C2=A0 And =
if
> they are, running a userspace test should be able to detect if the
> feature is present or not by the error returned to it, right?=C2=A0 If no=
t,
> then the feature is mis-designed.

Thank you for the explanation. (I didn't know these tests had to support "e=
nterprise" kernels.)

For features where the userspace explicitly asks to use them, that's easy. =
For events that are only created from a specific kernel version, that will =
be harder but it is maybe a sign that something else is missing on our side=
 :)

>> That's how we thought we should design MPTCP selftests. Maybe we need to=
 change this design?
>
> Yes, please "skip" tests for features that are just not present, do not
> fail them.

It might take a bit of time but we will look at that. I think we don't even=
 check MPTCP is available before starting the first test, we just assume it=
 is there if someone explicitly starts these tests :-)

>> Is it a common practice to run selftests' latest version on older kernel=
s?
>
> Yes.

Thank you, I didn't know (and I don't know if it is well known by kernel de=
vs and maintainers).

Cheers,
Matt
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