Re: [Xen-devel] [PATCH v3] xen: introduce VCPUOP_register_runstate_phys_memory_area hypercall

[Julien Grall <julien.grall@xxxxxxx>]

On 14/06/2019 17:11, Andrii Anisov wrote:
> On 14.06.19 18:24, Julien Grall wrote:
> > But, if you allow something, then most likely someone will use it. However, 
> > you have to differentiate implementation vs documentation.
> > In this case, I don't think the implementation should dictate what is going to 
> > be exposed.
> > If you document that it can't happen, then you have room to forbid the mix in 
> > the future (assuming this can't be done now).
> > In other word, the more lax is the interface, the more difficult it is tighten 
> > in the future.
> > I am not going to push for an implementation that forbid the mix. But I am 
> > strongly going to push for any documentation of the expected interaction. So 
> > we don't make our life miserable later on.
> I do not encourage using both interfaces simultaneously, it is pointless.
> If you are saying that this matter could be solved with the appropriate 
> documentation, it's OK with me.
> > > BTW, dropping the old interface implementation will be much easier in future 
> > > if it will not clash with the new one.
> > I am afraid we will never be able to remove the old interface.
> Maybe.
Well, that a stable ABI... Even if I would love to remove it, you can't get rid 
of old guests that easily...
Cheers,


>
--
Julien Grall

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