[Skiboot] [PATCH] core/init: Add ibm, processor-storage-keys property to CPU DT node.

[Michael Ellerman]

Thiago Jung Bauermann <bauerman at linux.vnet.ibm.com> writes:

> LoPAPR says:
>
>     “ibm,processor-storage-keys”
>
>     property name indicating the number of virtual storage keys supported
>     by the processor described by this node.
>
>     prop-encoded-array: Consists of two cells encoded as with encode-int.
>     The first cell represents the number of virtual storage keys supported
>     for data accesses while the second cell represents the number of
>     virtual storage keys supported for instruction accesses. The cell value
>     of zero indicates that no storage keys are supported for the access
>     type.
>
> pHyp provides the property above but there's a bug in P8 firmware where the
> second cell is zero even though POWER8 supports instruction access keys.
> This bug will be fixed for P9.
>
> While this is a PAPR property, it's useful to have it in powernv as well
> so that Linux has a uniform way of checking for the feature regardless of
> the platform it's running on.

True.

Though having it in every CPU node is kind of annoying. There's no way
we're ever going to support a different number of keys on different CPUs
in the system.

We could put it under the /ibm,opal node, that would require checking
there in the Linux code, but it should be ~= 2 extra lines so not a big
deal.

I dunno, maybe we should follow PAPR exactly, but it just seems silly to
copy the property for every CPU in the system.

Does skiboot want to reserve some keys for itself ?

cheers