From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1422823AbWJTT4V (ORCPT ); Fri, 20 Oct 2006 15:56:21 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1422831AbWJTT4V (ORCPT ); Fri, 20 Oct 2006 15:56:21 -0400 Received: from palrel11.hp.com ([156.153.255.246]:30403 "EHLO palrel11.hp.com") by vger.kernel.org with ESMTP id S1422823AbWJTT4U (ORCPT ); Fri, 20 Oct 2006 15:56:20 -0400 Date: Fri, 20 Oct 2006 14:56:18 -0500 From: "Mike Miller (OS Dev)" To: Andrew Morton , jens.axboe@oracle.com Cc: linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org Subject: Re: [PATCH 2/2] cciss: disable dma prefetch for P600 Message-ID: <20061020195618.GA13181@beardog.cca.cpqcorp.net> References: <20061017211303.GB17874@beardog.cca.cpqcorp.net> <20061017171021.baea3c3f.akpm@osdl.org> <20061018165453.GA14255@beardog.cca.cpqcorp.net> <20061018143723.48510ea7.akpm@osdl.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20061018143723.48510ea7.akpm@osdl.org> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 18, 2006 at 02:37:23PM -0700, Andrew Morton wrote: > > argh, you removed the mailing list from cc. Sorry, I'm still lacking proper etiquette. > > On Wed, 18 Oct 2006 11:54:53 -0500 > "Mike Miller (OS Dev)" wrote: > > > On Tue, Oct 17, 2006 at 05:10:21PM -0700, Andrew Morton wrote: > > > On Tue, 17 Oct 2006 16:13:03 -0500 > > > "Mike Miller (OS Dev)" wrote: > > > > > > > PATCH 2/2 > > > > Turned off DMA prefetch for the P600 on systems which may present > > > > discontiguous memory. > > > > > > > > > > What do you mean by "discontiguous memory"? CONFIG_DISCONTIGMEM? > > > > The IPF memory map can have holes between the different regions. I've > > been told by our HW guys that AMD may also have holes. > > Pretty much all platforms/architectures have holes in their physical memory > map. > > > > > > > > What is the actual problem which is being fixed here? > > > > Sorry, I should have been clearer. There is a bug in the DMA engine that > > that may result in prefetching data from beyond the end of memory or > > falling off into one the holes on IPF and AMD. It causes a machine check > > when that happens. > > It doesn't happen on Proliant because the last 4kB (or so) of memory is > > mapped out by the BIOS and Pentium guarantees contiguous memory. > > I think that this: > > > > #if defined(CONFIG_IA64) || defined(CONFIG_X86_64) > > is nowhere near strong enough and is probably inappropriate. > > It _could_ be that CONFIG_DISCONTIGMEM|CONFIG_SPARSEMEM will be closer, but > even CONFIG_FLATMEM systems can have holes. I'm poking around on some IPF platforms. It looks like CONFIG_DISCONTIGMEM is set on them, but not the others you mention. Would that be sufficient? > > On what machines can/does this card exist? Things like powerpc? This problem was found on Itanium. We don't try to support powerpc. Thanks, mikem