From mboxrd@z Thu Jan 1 00:00:00 1970 From: Segher Boessenkool Subject: Re: [patch 5/6] ps3: BD/DVD/CD-ROM Storage Driver Date: Mon, 16 Jul 2007 14:08:57 +0200 Message-ID: <0A74AFF2-CBDA-4B00-AF5F-B6C6DACE0E16@kernel.crashing.org> References: <20070704132212.726923000@pademelon.sonytel.be> <1184335333.3402.20.camel@localhost.localdomain> <200707131619.54898.arnd@arndb.de> <1184368328.6059.271.camel@localhost.localdomain> Mime-Version: 1.0 (Apple Message framework v752.2) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from gate.crashing.org ([63.228.1.57]:53949 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754804AbXGPMJ4 (ORCPT ); Mon, 16 Jul 2007 08:09:56 -0400 In-Reply-To: <1184368328.6059.271.camel@localhost.localdomain> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Benjamin Herrenschmidt Cc: Arnd Bergmann , James Bottomley , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, Alessandro Rubini , linuxppc-dev@ozlabs.org, Paul Mackerras , Jens Axboe , Geert Uytterhoeven >> I'm pretty sure that no ppc64 machine needs alias resolution in >> the kernel, >> although some are VIPT. Last time we discussed this, Segher >> explained it >> to me, but I don't remember which way Cell does it. IIRC, it >> automatically >> flushes cache lines that are accessed through aliases. > > Ah yes, I remember reading about this automatic flushing thing. I > don't > know how the caches actually work on most of our PPC's, but the > fact is, > we don't have aliasing issues, so I can safely ignore it for a bit > longer :-) That is the very short version of the story, yes: some PowerPC implementations are VIPT physically, but there are no aliasing issues we have to worry about. Anyone interested in how this works, can download the PPC970 UM (or 970FX or 970MP); it has a very detailed explanation of all this. Cell might be slightly different but the base idea is the same. Segher