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 AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 26B321A017D for ; Mon, 15 Feb 2016 14:21:31 +1100 (AEDT) Date: Mon, 15 Feb 2016 14:21:24 +1100 From: Paul Mackerras To: "Aneesh Kumar K.V" Cc: benh@kernel.crashing.org, mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org Subject: Re: [PATCH V2 07/29] mm: Make vm_get_page_prot arch specific. Message-ID: <20160215032124.GB3797@oak.ozlabs.ibm.com> References: <1454923241-6681-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1454923241-6681-8-git-send-email-aneesh.kumar@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1454923241-6681-8-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 Mon, Feb 08, 2016 at 02:50:19PM +0530, Aneesh Kumar K.V wrote: > With next generation power processor, we are having a new mmu model > [1] that require us to maintain a different linux page table format. > > Inorder to support both current and future ppc64 systems with a single > kernel we need to make sure kernel can select between different page > table format at runtime. With the new MMU (radix MMU) added, we will > have to dynamically switch between different protection map. Hence > override vm_get_page_prot instead of using arch_vm_get_page_prot. We > also drop arch_vm_get_page_prot since only powerpc used it. What's different about ISA v3.0 that means that the protection_map[] entries need to be different? If it's just different bit assignments for things like _PAGE_READ etc., couldn't we fix this up at early boot time by writing new values into protection_map[]? Is there a reason why that wouldn't work, or why you don't want to do that? Paul.