Re: [Qemu-devel] [PATCH 4/9] s390x: refactor error handling for SSCH and RSCH

[Halil Pasic]

On 09/06/2017 04:20 PM, Cornelia Huck wrote:
> On Wed, 6 Sep 2017 14:25:13 +0200
> Halil Pasic <address@hidden> wrote:
> 
>> We have basically two possibilities/options which ask for different
>> handling:
>> 1) EFAULT is due to a bug in the vfio-ccw implementation
>> (can be QEMU or kernel).
>> 2) EFAULT is due to buggy channel program.
>>
>> Option 2) is basically to be handled with a channel-program check and
>> setting primary secondary and alert status. For reference see PoP page
>> 15-59 ("Designation of Storage Area").  An exception may be an invalid
>> channel program address in the ORB. There the channel-program check ain't
>> explicitly stated (although) I would expect one. It may be implied by the
>> things on page 15-59 though.
>>
>> Option 1) is however very similar to other we have figured out that the
>> implementation is broken situations and should be handled consequently.
>> The current state of the discussion is with a unit exception.
>>
>> Does that make sense?
> 
> I think the situation is slightly different here, though. For the orb
> flags, we reject something out of hand because we have not implemented
> it, and for that, unit exception sounds like a good fit. Processing
> errors, however, are more similar to errors in the hardware, and as
> such can probably be reported via something like equipment check.
> 

Noted. Let's see what Dong Jia has to say, before we continuing a
discussion on something (option 1) what may be irrelevant anyway.

>>
>> Now, Dong Jia, I need your help to figure out do we have option 1 or
>> option 2 here? After quick look at the kernel code, it appears to me that
>> I've seen both option 1 and option 2 (I'm afraid) -- but my assessment
>> was really very superficial.
>>
>> I would expect option 2 to be handled differently (kernel provides the
>> SCSW) though.
>>
>> Regards,
>> Halil
>>
> 
>