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

David Hildenbrand
2024-10-15T08:16:26Z

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