Re: [Qemu-devel] [PATCH 5/5] s390x/ccs: add ccw-tester emulated device

[Halil Pasic <pasic@linux.vnet.ibm.com>]

On 09/06/2017 03:18 PM, Cornelia Huck wrote:
> On Tue,  5 Sep 2017 13:16:45 +0200
> Halil Pasic <pasic@linux.vnet.ibm.com> wrote:
> 
>> Add a fake device meant for testing the correctness of our css emulation.
>>
>> What we currently have is writing a Fibonacci sequence of uint32_t to the
>> device via ccw write. The write is going to fail if it ain't a Fibonacci
>> and indicate a device exception in scsw together with the proper residual
>> count.
>>
>> Of course lot's of invalid inputs (besides basic data processing) can be
>> tested with that as well.
>>
>> Usage:
>> 1) fire up a qemu with something like -device ccw-tester,devno=fe.0.0001
>>    on the command line
>> 2) exercise the device from the guest
>>
>> Signed-off-by: Halil Pasic <pasic@linux.vnet.ibm.com>
>> ---
>>
>> It may not make sense to merge this work in the current form, as it is
>> solely for test purposes.
>> ---
>>  hw/s390x/Makefile.objs |   1 +
>>  hw/s390x/ccw-tester.c  | 179 +++++++++++++++++++++++++++++++++++++++++++++++++
>>  2 files changed, 180 insertions(+)
>>  create mode 100644 hw/s390x/ccw-tester.c
> 
> The main problem here is that you want to exercise a middle layer (the
> css code) and need to write boilerplate code on both host and guest
> side in order to be able to do so.
> 

Nod.

> In general, a device that accepts arbitrary channel programs looks
> useful for testing purposes. I would split out processing of expected
> responses out, though, so that it can be more easily reused for
> different use cases.
> 

I'm not sure what do you mean here. Could you clarify please?

> (I dimly recall other test devices...)
> 

What's on your mind? How do these relate to our problem? Can you
give me some pointers?

> For the guest tester: Can that be done via the qtest infrastructure
> somehow?
> 

Well, for now I have the out-of-tree Linux kernel module provided in the
cover letter of the series (you did not comment on that one yet).

I think for building trust regarding my IDA implementation it should be
able to do the job. Don't you agree?

Just a couple of hours ago Janosch (cc-ing Janosch) came to my office,
and told be that he is working on CCW-tests for zonk (a minimal kernel
for testing -- internal tool AFAIR).

By qtest you mean libqtest/libqos? I'm not familiar with that and have no
idea what do we have for s390x. I see on libqos-s390x file in test/libqos
for starters.

Regards,
Halil