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From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
To: Ram Pai <linuxram@us.ibm.com>, mpe@ellerman.id.au,
 linuxppc-dev@lists.ozlabs.org
Cc: benh@kernel.crashing.org, paulus@samba.org, khandual@linux.vnet.ibm.com,
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 bauerman@linux.vnet.ibm.com, ebiederm@xmission.com, linuxram@us.ibm.com
Subject: Re: [PATCH 03/25] powerpc: track allocation status of all pkeys
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Ram Pai <linuxram@us.ibm.com> writes:

> Total 32 keys are available on power7 and above. However
> pkey 0,1 are reserved. So effectively we  have  30 pkeys.

When you say reserved, reserved by whom? Is that part of ISA or PAPR ?
Also do you expect that to change. If not why all these indirection?
Can we have the mask as a #define for 4K and 64K page size
config?

>
> On 4K kernels, we do not  have  5  bits  in  the  PTE to
> represent  all the keys; we only have 3bits.Two of those
> keys are reserved; pkey 0 and pkey 1. So effectively  we
> have 6 pkeys.
>
> This patch keeps track of reserved keys, allocated  keys
> and keys that are currently free.
>
> Also it  adds  skeletal  functions  and macros, that the
> architecture-independent code expects to be available.


-aneesh