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

[Cornelia Huck]

On Thu, 7 Sep 2017 15:31:09 +0800
Dong Jia Shi <address@hidden> wrote:

> * Cornelia Huck <address@hidden> [2017-09-06 15:18:21 +0200]:
> 
> > 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?
> >   
> 
> I'm thinking of a method these days:
> Could passing through an fully emulated ccw device (e.g. 3270), or a
> virtio ccw device, in the level 1 kvm guest to a level 2 guest be a test
> method for this?
> 
> All of the CCWs will be translated to IDAL CCWs by vfio-ccw in the level
> 1 guest (which is the level 2 kvm host) and issued to the level 1 kvm
> host. So, those IDALs will eventually be handled by the emulated device,
> or the virtio ccw device, on the level 1 kvm host...
> 
> Some days ago, one of my colleague tried the emulated 3270 passing
> through. She stucked with the problem that the level 1 kvm host handling
> a senseid IDAL ccw as a Direct ccw.
> 
> Maybe I could try to pass through a virtio ccw device. I don't think of
> any obvious problem that would lead to fail. Any comment?
> 

That actually looks like a good thing to try! Cool idea.