From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265342AbTFFG2y (ORCPT ); Fri, 6 Jun 2003 02:28:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S265344AbTFFG2y (ORCPT ); Fri, 6 Jun 2003 02:28:54 -0400 Received: from palrel12.hp.com ([156.153.255.237]:55515 "EHLO palrel12.hp.com") by vger.kernel.org with ESMTP id S265342AbTFFG2x (ORCPT ); Fri, 6 Jun 2003 02:28:53 -0400 From: David Mosberger MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <16096.14281.621282.67906@napali.hpl.hp.com> Date: Thu, 5 Jun 2003 23:42:17 -0700 To: manfred@colorfullife.com Cc: axboe@suse.de, davidm@hpl.hp.com, "David S. Miller" , linux-kernel@vger.kernel.org Subject: Re: problem with blk_queue_bounce_limit() In-Reply-To: <1054797653.18294.1.camel@rth.ninka.net> References: <16094.58952.941468.221985@napali.hpl.hp.com> <1054797653.18294.1.camel@rth.ninka.net> X-Mailer: VM 7.07 under Emacs 21.2.1 Reply-To: davidm@hpl.hp.com X-URL: http://www.hpl.hp.com/personal/David_Mosberger/ Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org >>>>> On 05 Jun 2003 00:20:53 -0700, "David S. Miller" said: DaveM> On Wed, 2003-06-04 at 23:42, David Mosberger wrote: >> On platforms with I/O MMU hardware, memory above 4GB, and IDE hard disks, >> this check: >> BUG_ON(dma_addr < BLK_BOUNCE_ISA); DaveM> Doesn't panic on sparc64, let this be your guiding light :-) I checked with Dave in private email and, like I suspected, this is a (potential) problem on sparc64 as well. Let me be try to be even more clear: on many 64 bit platforms, BLK_BOUNCE_ISA will be bigger than 4GB, so the BUG_ON() will trigger for IDE controllers that can DMA only to, say, 4GB (and it's probably not even an IDE-only problem, I think we don't see it on SCSI because our machines have SCSI controllers that can DMA >4GB). Manfred, I'm readdressed this mail to you because according to google, you're the original author of the patch (http://www.cs.helsinki.fi/linux/linux-kernel/2002-02/0032.html). Like I stated earlier, I think this code simply makes no sense on a platform with I/O MMU. Hence my suggestion to deal with this via dma_supported(). --david