Re: [PATCH RFCv3 6/9] s390x/diag: subcode to query device memory region

[David Hildenbrand]

On 27.07.20 13:15, Heiko Carstens wrote:
> On Mon, Jul 27, 2020 at 12:12:02PM +0200, David Hildenbrand wrote:
>>>>>> +#define DIAG500_DEVICE_MEMORY_REGION   4  
>>>>>
>>>>> Regardless what we end up with, this needs to be specified
>>>>> somewhere(tm).
>>>>
>>>> Yeah, there, we should also document the existing subcodes. What would
>>>> be the right place for this? The kernel feels somewhat wrong to me.
>>>
>>> The still supported subcode 3 is properly specified in the virtio spec.
>>> That's not a good place for that new one, though.
>>>
>>> QEMU is probably a better place than the kernel to specify stuff,
>>> although it's not really ideal, either. OTOH, do we ever expect other
>>> hypervisors to implement this new subcode?
>>
>> cloud-hypervisor implements virtio-mem. If it were ever to support s390x
>> (guess it does not yet), it would also want to implement that one. But
>> then, it can just look at QEMU doc I guess :)
> 
> It must be well defined and easy to find also for kernel developers
> who actually have to care about memory detection code :)

So I'd suggest documenting it in QEMU (docs/specs ...) for now, and
referencing it from the relevant Linux patch - other suggestions?

-- 
Thanks,

David / dhildenb