Re: [Qemu-devel] [PATCH 2/9] s390x: fix invalid use of cc 1 for SSCH

[Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>]

* Cornelia Huck <cohuck@redhat.com> [2017-09-05 17:46:06 +0200]:

> On Tue, 5 Sep 2017 17:24:19 +0200
> Halil Pasic <pasic@linux.vnet.ibm.com> wrote:
> 
> > My problem with a program check (indicated by SCSW word 2 bit 10) is
> > that, in my reading of the architecture, the semantic behind it is: The
> > channel subsystem (not the cu or device) has detected, that the 
> > the channel program (previously submitted as an ORB) is erroneous. Which
> > programs are erroneous is specified by the architecture. What we have
> > here does not qualify.
> > 
> > My idea was to rather blame the virtual hardware (device) and put no blame
> > on the program nor he channel subsystem. This could be done using device
> > status (unit check with command reject, maybe unit exception) or interface
> > check. My train of thought was, the problem is not consistent across a
> > device type, so it has to be device specific.
> 
> Unit exception might be a better way to express what is happening here.
> At least, it moves us away from cc 1 and not towards cc 3 :)
> 
> > 
> > Of course blaming the device could mislead the person encountering the
> > problem, and make him believe it's an non-virtual hardware problem.
> > 
> > About the misleading, I think the best we can do is log out a message
> > indicating what really happened.
> 
> Just document it in the code? If it doesn't happen with Linux as a
> guest, it is highly unlikely to be seen in the wild.
> 
> > 
> > In the end I don't care that deeply about vfio-ccw, and this problem
> > already took me more time than I intended to spend on this. We have
> > people driving this whole vfio-ccw stuff and I'm not one of them (I'm
> > rather in the supporting role).
> > 
> > I'm also fine with me being credited with a reported-by once the
> > more involved people figure out what to do, and keeping the vfio-ccw
> > stuff as is. Should we go with that option? 
> 
> If converting the reporting to a device status is straightforward
> enough, let's do that. I'm fine with postponing this and waiting for a
> real fix as well (I don't really have spare cycles to actually write
> vfio-ccw code currently...)
> 

I can do this after this series.

[...]

-- 
Dong Jia Shi