Re: [PATCH v2 2/7] Documentation: s390-diag.rst: make diag500 a generic KVM hypercall

[David Hildenbrand]

On 15.10.24 10:12, Heiko Carstens wrote:
> On Mon, Oct 14, 2024 at 09:35:27PM +0200, David Hildenbrand wrote:
> > On 14.10.24 20:04, Heiko Carstens wrote:
> > > On Mon, Oct 14, 2024 at 04:46:14PM +0200, David Hildenbrand wrote:
> > > If so, it would be nice to document that too; but that is not
> > > necessarily your problem.
> >
> > I can squash:
> >
> > diff --git a/Documentation/virt/kvm/s390/s390-diag.rst b/Documentation/virt/kvm/s390/s390-diag.rst
> > index d9b7c6cbc99e..48a326d41cc0 100644
> > --- a/Documentation/virt/kvm/s390/s390-diag.rst
> > +++ b/Documentation/virt/kvm/s390/s390-diag.rst
> > @@ -50,6 +50,9 @@ Upon completion of the DIAGNOSE instruction, general register 2 contains
> >   the function's return code, which is either a return code or a subcode
> >   specific value.
> > +If the specified subfunction is not supported, a SPECIFICATION exception
> > +will be triggered.
> > +
>
> Looks good. Thanks!
>
> > > I guess we won't see too many new diag 500 subcodes, or would it make
> > > sense to implement some query subcode?
> >
> > In the context of STORAGE LIMIT, a "query" subfunction is not really beneficial:
> >
> > it's either one invocation of "query", conditionally followed by one invocation of "STORAGE LIMIT"
> > vs. one invocation of "STORAGE LIMIT".
> >
> > Once there might be a bunch of other subfunctions, a "query" might make more sense.
>
> "If only there would be a query subcode available, so that the program
> check handling would not be necessary; but in particular my new subcode
> is not worth adding it" :)
>
> Anyway, I do not care too much.

Okay, I see your point: it would allow for removing the program check 
handling from the STORAGE LIMIT invocation.

... if only we wouldn't need the exact same program check handling for 
the new query subfunction :P

--
Cheers,

David / dhildenb