From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e19.ny.us.ibm.com (e19.ny.us.ibm.com [129.33.205.209]) (using TLSv1.2 with cipher CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 9CC601A0668 for ; Fri, 19 Feb 2016 13:40:11 +1100 (AEDT) Received: from localhost by e19.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 18 Feb 2016 21:40:09 -0500 Received: from b01cxnp22035.gho.pok.ibm.com (b01cxnp22035.gho.pok.ibm.com [9.57.198.25]) by d01dlp02.pok.ibm.com (Postfix) with ESMTP id 9A38A6E8041 for ; Thu, 18 Feb 2016 21:26:58 -0500 (EST) Received: from d01av05.pok.ibm.com (d01av05.pok.ibm.com [9.56.224.195]) by b01cxnp22035.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id u1J2e60i30277816 for ; Fri, 19 Feb 2016 02:40:06 GMT Received: from d01av05.pok.ibm.com (localhost [127.0.0.1]) by d01av05.pok.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id u1J2aREr030807 for ; Thu, 18 Feb 2016 21:36:28 -0500 From: "Aneesh Kumar K.V" To: Paul Mackerras Cc: benh@kernel.crashing.org, mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org Subject: Re: [PATCH V3 01/30] mm: Make vm_get_page_prot arch specific. In-Reply-To: <20160218231546.GC2765@fergus.ozlabs.ibm.com> References: <1455814254-10226-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <1455814254-10226-2-git-send-email-aneesh.kumar@linux.vnet.ibm.com> <20160218231546.GC2765@fergus.ozlabs.ibm.com> Date: Fri, 19 Feb 2016 08:10:00 +0530 Message-ID: <87egc9e83j.fsf@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Paul Mackerras writes: > On Thu, Feb 18, 2016 at 10:20:25PM +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. > > This seems like unnecessary churn to me. Let's just make hash use the > same values as radix for things like _PAGE_RW, _PAGE_EXEC etc., and > then we don't need any of this. > I was hoping to do that after this series. Something similar to https://github.com/kvaneesh/linux/commit/0c2ac1328b678a6e187d1f2644a007204c59a047 " powerpc/mm: Add helper for page flag access in ioremap_at Instead of using variables we use static inline which get patched during boot to either hash or radix version. " That gives us a base to revert patches if we find issues with hash and still have a working radix base. So idea is to introduce radix with minimal changes to hash and then consolidate hash and radix as much as we can by updating hash linux format. -aneesh