Re: [PATCH v4 1/7] s390: ap: kvm: add PQAP interception for AQIC

[Pierre Morel]

On 28/02/2019 14:52, Cornelia Huck wrote:
> On Thu, 28 Feb 2019 14:16:09 +0100
> Pierre Morel <pmorel@xxxxxxxxxxxxx> wrote:
>
> > On 28/02/2019 12:22, Cornelia Huck wrote:
>
> > > So, to summarize, the function should do:
> > > - Is userspace supposed to emulate everything (!ECA_APIE)? Return
> > >     -EOPNOTSUPP to hand control to it.
> > > - We are now interpreting the instruction in KVM. Do common checks
> > >     (PSTATE etc.) and inject exceptions, if needed.
> > > - Now look at the fc; if there's a handler for it, call that; if not
> > >     (case does not attempt to call a specific handler, or no handler
> > >     registered), inject a specification exception. (Do we want pre-checks
> > >     like for facility 65 here, or in the handler?)
> > >
> > > That response code 0x01 thingy probably needs to go into the specific
> > > handler function, if anywhere (don't know the semantics, sorry).
> >
> > What do you mean with specific handler function?
> >
> > If you mean a switch around the FC with static function's call, I agree,
> > if you mean a jump into a hook I do not agree.
>
> Ah, ok; so each case (that we want to handle) should call into a
> subhandler that does
> {
> 	(... check things like facilities ...)
> 	if (!specific_hook)
> 		inject_specif_excp_and_return();
> 	ret = specific_hook();
> 	if (ret)
> 		set_resp_code_0x01(); // or in specific_hook()?
> }
>
> ?

Yes something in this direction.

>   
> > > Question: Will the handlers for the individual fcs need to generate
> > > different exceptions on their own? I.e., do they need to do injections
> > > themselves, or should the calling function possibly inject an exception
> > > on error?
> >
> > There are some specificities.
>
> Ok, should probably done in the subhandlers?
>
> (I hope I don't muddy the waters too much; but basically, I'm poking
> around with a stick in the dark :)

No problem, it is OK.
My first idea was to make only changes associated with PQAP/AQIC.
We already should have done it for all PQAP functions so it is decided 
that we will do it now as Christian proposed.

Regards,
Pierre


--
Pierre Morel
Linux/KVM/QEMU in BÃblingen - Germany