Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263459AbTGATth (ORCPT ); Tue, 1 Jul 2003 15:49:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263496AbTGATth (ORCPT ); Tue, 1 Jul 2003 15:49:37 -0400 Received: from nat9.steeleye.com ([65.114.3.137]:11525 "EHLO hancock.sc.steeleye.com") by vger.kernel.org with ESMTP id S263459AbTGATtg (ORCPT ); Tue, 1 Jul 2003 15:49:36 -0400 Subject: Re: [RFC] block layer support for DMA IOMMU bypass mode From: James Bottomley To: Grant Grundler Cc: Jens Axboe , ak@suse.de, davem@redhat.com, suparna@in.ibm.com, Linux Kernel , Alex Williamson , Bjorn Helgaas In-Reply-To: <20030701191941.GF14683@dsl2.external.hp.com> References: <1057077975.2135.54.camel@mulgrave> <20030701191941.GF14683@dsl2.external.hp.com> Content-Type: text/plain Content-Transfer-Encoding: 7bit X-Mailer: Ximian Evolution 1.0.8 (1.0.8-9) Date: 01 Jul 2003 15:03:45 -0500 Message-Id: <1057089827.2003.110.camel@mulgrave> Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1161 Lines: 26 On Tue, 2003-07-01 at 14:19, Grant Grundler wrote: > On Tue, Jul 01, 2003 at 11:46:12AM -0500, James Bottomley wrote: > > +/* Is the queue dma_mask eligible to be bypassed */ > > +#define __BIO_CAN_BYPASS(q) \ > > + ((BIO_VMERGE_BYPASS_MASK) && ((q)->dma_mask & (BIO_VMERGE_BYPASS_MASK)) == (BIO_VMERGE_BYPASS_MASK)) > > Like Andi, I had suggested a callback into IOMMU code here. > But I'm pretty sure james proposal will work for ia64 and parisc. OK, the core of my objection to this is that at the moment there's no entangling of the bio layer and the DMA layer. The bio layer works with a nice finite list of generic or per-queue constraints; it doesn't care currently what the underlying device or IOMMU does. Putting such a callback in would add this entanglement. It could be that the bio people will be OK with this, and I'm just worrying about nothing, but in that case, they need to say so... James - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/