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From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
To: Paul Mackerras via Linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
 linuxppc-dev@lists.ozlabs.org
Cc: Michael Ellerman <mpe@ellerman.id.au>, Paul Mackerras <paulus@samba.org>
Subject: Re: [RFC PATCH 2/9] powerpc/mm/book3s-64: Free up 7 high-order bits
 in the Linux PTE
In-Reply-To: <1455948760-24710-3-git-send-email-paulus@samba.org>
References: <1455948760-24710-1-git-send-email-paulus@samba.org>
 <1455948760-24710-3-git-send-email-paulus@samba.org>
Date: Sat, 20 Feb 2016 21:46:19 +0530
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Paul Mackerras <paulus@samba.org> writes:

> This frees up bits 57-63 in the Linux PTE on 64-bit Book 3S machines.
> In the 4k page case, this is done just by reducing the size of the
> RPN field to 39 bits, giving 51-bit real addresses.  In the 64k page
> case, we had 10 unused bits in the middle of the PTE, so this moves
> the RPN field down 10 bits to make use of those unused bits.  This
> means the RPN field is now 3 bits larger at 37 bits, giving 53-bit
> real addresses in the normal case, or 49-bit real addresses for the
> special 4k PFN case.


Is it ok to have different real address bits between 4k and 64k linux
config ?

-aneesh