Re: [PATCH v2 04/14] spapr: nested: Introduce cap-nested-papr for Nested PAPR API

[Nicholas Piggin]

On Thu Oct 12, 2023 at 8:49 PM AEST, Harsh Prateek Bora wrote:
> Introduce a SPAPR capability cap-nested-papr which provides a nested
> HV facility to the guest. This is similar to cap-nested-hv, but uses
> a different (incompatible) API and so they are mutually exclusive.
> This new API is to enable support for KVM on PowerVM and recently the
> Linux kernel side patches have been accepted upstream as well [1].
> Support for related hcalls is being added in next set of patches.

We do want to be able to support both APIs on a per-guest basis. It
doesn't look like the vmstate bits will be a problem, both could be
enabled if the logic permitted it and that wouldn't cause a
compatibility problem I think?

And it's a bit of a nitpick, but the capability should not be permitted
before the actual APIs are supported IMO. You could split this into
adding .api first, so the implementation can test it, and add the spapr
caps at the end.

Thanks,
Nick