Re: Plan for hybrid testing

[shuah <shuah@kernel.org>]

On 10/14/19 12:38 PM, Knut Omang wrote:
> On Mon, 2019-10-14 at 10:42 +0000, Luis Chamberlain wrote:
>> On Fri, Sep 13, 2019 at 02:02:47PM -0700, Brendan Higgins wrote:
>>> Hey Knut and Shuah,
>>>
>>> Following up on our offline discussion on Wednesday night:
>>>
>>> We decided that it would make sense for Knut to try to implement Hybrid
>>> Testing (testing that crosses the kernel userspace boundary) that he
>>> introduced here[1] on top of the existing KUnit infrastructure.
>>>
>>> We discussed several possible things in the kernel that Knut could test
>>> with the new Hybrid Testing feature as an initial example. Those were
>>> (in reverse order of expected difficulty):
>>>
>>> 1. RDS (Reliable Datagram Sockets) - We decided that, although this was
>>>     one of the more complicated subsystems to work with, it was probably
>>>     the best candidate for Knut to start with because it was in desperate
>>>     need of better testing, much of the testing would require crossing
>>>     the kernel userspace boundary to be effective, and Knut has access to
>>>     RDS (since he works at Oracle).
>>>

Any update on if you are able to explore this work.

>>> 2. KMOD - Probably much simpler than RDS, and the maintainer, Luis
>>>     Chamberlain (CC'ed) would like to see better testing here, but
>>>     probably still not as good as RDS because it is in less dire need of
>>>     testing, collaboration on this would be more difficult, and Luis is
>>>     currently on an extended vacation. Luis and I had already been
>>>     discussing testing KMOD here[2].
>>
>> I'm back!
>>
>> I'm also happy and thrilled to help review the infrastructure in great
>> detail given I have lofty future objectives with testing in the kernel.
>> Also, kmod is a bit more complex to test, if Knut wants a simpler *easy*
>> target I think test_sysctl.c would be a good target. I think the goal
>> there would be to add probes for a few of the sysctl callers, and then
>> test them through userspace somehow, for instance?
> 
> That sounds like a good case for the hybrid tests.
> The challenge in a kunit setting would be that it relies on a significant part of KTF
> to work as we have used it so far:
> 
> - module support - Alan has been working on this

I see the patches. Thanks for working on this.

> - netlink approach from KTF (to allow user space execution of kernel
>    part of test, and gathering reporting in one place)
> - probe infrastructure
> 
>> The complexities with testing kmod is the threading aspect. So that is
>> more of a challenge for a test infrastructure as a whole. However kmod
>> also already has a pretty sound kthread solution which could be used
>> as basis for any sound kernel multithread test solution.
>>
>> Curious, what was decided with the regards to the generic netlink approach?
> 

Can this work be be done without netlink approach? At least some of it.
I would like to see some patches and would like to get a better feel
for the dependency on generic netlink.

> I think in some way functionality similar to the netlink support is needed
> for the features in KTF that we discussed, so I get it is a "yes" to add
> support for it?
> 

See above.

thanks,
-- Shuah