From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756668AbbIYOr6 (ORCPT ); Fri, 25 Sep 2015 10:47:58 -0400 Received: from smtp-out4.electric.net ([192.162.216.186]:63315 "EHLO smtp-out4.electric.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756564AbbIYOr4 (ORCPT ); Fri, 25 Sep 2015 10:47:56 -0400 From: David Laight To: "'Scott Wood'" CC: "'Christophe Leroy'" , Benjamin Herrenschmidt , Paul Mackerras , "Michael Ellerman" , "linuxppc-dev@lists.ozlabs.org" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH v2 08/25] powerpc/8xx: Map IMMR area with 512k page at a fixed address Thread-Topic: [PATCH v2 08/25] powerpc/8xx: Map IMMR area with 512k page at a fixed address Thread-Index: AQHQ9ViIWkdjaYZFDUelHW1RqGORq55Lj53ggACAI4CAAUa38A== Date: Fri, 25 Sep 2015 14:46:40 +0000 Message-ID: <063D6719AE5E284EB5DD2968C1650D6D1CBA2CBE@AcuExch.aculab.com> References: <063D6719AE5E284EB5DD2968C1650D6D1CBA15B8@AcuExch.aculab.com> <1443125663.32298.32.camel@freescale.com> In-Reply-To: <1443125663.32298.32.camel@freescale.com> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.202.99.200] Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 X-Outbound-IP: 213.249.233.130 X-Env-From: David.Laight@ACULAB.COM X-PolicySMART: 3396946, 3397078 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id t8PEm2or030136 From: Scott Wood > Sent: 24 September 2015 21:14 > > Isn't this a more general problem? > > > > If there are multiple remap requests for the same physical page > > shouldn't the kernel be just increasing a reference count somewhere > > and returning address in the same virtual page? > > This should probably happen regardless of the address. > > I presume it must be done for cacheable mappings. > > Why would you assume that? Because 'really horrid (tm)' things happen on some cache architectures if you map the same physical address to multiple virtual addresses. David {.n++%ݶw{.n+{G{ayʇڙ,jfhz_(階ݢj"mG?&~iOzv^m ?I