From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932544AbaHGPcO (ORCPT ); Thu, 7 Aug 2014 11:32:14 -0400 Received: from mail-qg0-f53.google.com ([209.85.192.53]:60296 "EHLO mail-qg0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932330AbaHGPcK (ORCPT ); Thu, 7 Aug 2014 11:32:10 -0400 Date: Thu, 7 Aug 2014 11:32:07 -0400 (EDT) From: Nicolas Pitre To: Rob Herring cc: Max Filippov , Kees Cook , LKML , Mark Salter , Liu hua , Rabin Vincent , Nikolay Borisov , Leif Lindholm , Tomasz Figa , Doug Anderson , Will Deacon , Laura Abbott , Catalin Marinas , Russell King - ARM Linux , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH 1/7] arm: use generic fixmap.h In-Reply-To: Message-ID: References: <1407353564-21478-1-git-send-email-keescook@chromium.org> <1407353564-21478-2-git-send-email-keescook@chromium.org> User-Agent: Alpine 2.11 (LFD 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 7 Aug 2014, Rob Herring wrote: > On Thu, Aug 7, 2014 at 10:15 AM, Max Filippov wrote: > > Hi, > > > > On Wed, Aug 6, 2014 at 11:32 PM, Kees Cook wrote: > >> ARM is different from other architectures in that fixmap pages are indexed > >> with a positive offset from FIXADDR_START. Other architectures index with > >> a negative offset from FIXADDR_TOP. In order to use the generic fixmap.h > > > > Does anybody know if there's any reason why generic fixmap.h uses negative > > offsets? It complicates things with no obvious benefit if you e.g. try to align > > virtual address in the fixmap region with physical page color (that's why I've > > switched xtensa to positive fixmap addressing in v3.17). > > No, but each arch doing it differently is even more annoying. Why not switching everybody to positive offsets then? Nicolas From mboxrd@z Thu Jan 1 00:00:00 1970 From: nicolas.pitre@linaro.org (Nicolas Pitre) Date: Thu, 7 Aug 2014 11:32:07 -0400 (EDT) Subject: [PATCH 1/7] arm: use generic fixmap.h In-Reply-To: References: <1407353564-21478-1-git-send-email-keescook@chromium.org> <1407353564-21478-2-git-send-email-keescook@chromium.org> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, 7 Aug 2014, Rob Herring wrote: > On Thu, Aug 7, 2014 at 10:15 AM, Max Filippov wrote: > > Hi, > > > > On Wed, Aug 6, 2014 at 11:32 PM, Kees Cook wrote: > >> ARM is different from other architectures in that fixmap pages are indexed > >> with a positive offset from FIXADDR_START. Other architectures index with > >> a negative offset from FIXADDR_TOP. In order to use the generic fixmap.h > > > > Does anybody know if there's any reason why generic fixmap.h uses negative > > offsets? It complicates things with no obvious benefit if you e.g. try to align > > virtual address in the fixmap region with physical page color (that's why I've > > switched xtensa to positive fixmap addressing in v3.17). > > No, but each arch doing it differently is even more annoying. Why not switching everybody to positive offsets then? Nicolas