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

[Cornelia Huck]

On Tue,  5 Sep 2017 13:16:45 +0200
Halil Pasic <address@hidden> 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 <address@hidden>
> ---
> 
> 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.

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 dimly recall other test devices...)

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