From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from ozlabs.org (ozlabs.org [103.22.144.67]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3vsfgN5TwXzDqYB for ; Tue, 28 Mar 2017 16:33:04 +1100 (AEDT) Date: Tue, 28 Mar 2017 16:32:40 +1100 From: Paul Mackerras To: "Aneesh Kumar K.V" Cc: benh@kernel.crashing.org, mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org Subject: Re: [PATCH V3 09/10] powerpc/mm: Lower the max real address to 53 bits Message-ID: <20170328053240.cp4qlh3bphaxikxr@oak.ozlabs.ibm.com> References: <1490117400-9891-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1490117400-9891-9-git-send-email-aneesh.kumar@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1490117400-9891-9-git-send-email-aneesh.kumar@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, Mar 21, 2017 at 10:59:59PM +0530, Aneesh Kumar K.V wrote: > Max value supported by hardware is 51 bits address. Radix page table define > a slot of 57 bits for future expansion. We restrict the value supported in > linux kernel 53 bits, so that we can use the bits between 57-53 for storing > hash linux page table bits. This is done in the next patch. > > This will free up the software page table bits to be used for features > that are needed for both hash and radix. The current hash linux page table > format doesn't have any free software bits. Moving hash linux page table > specific bits to top of RPN field free up the software bits for other purpose. > > Signed-off-by: Aneesh Kumar K.V Reviewed-by: Paul Mackerras