From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263179AbTGARku (ORCPT ); Tue, 1 Jul 2003 13:40:50 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263185AbTGARku (ORCPT ); Tue, 1 Jul 2003 13:40:50 -0400 Received: from neon-gw-l3.transmeta.com ([63.209.4.196]:25615 "EHLO neon-gw.transmeta.com") by vger.kernel.org with ESMTP id S263179AbTGARkt (ORCPT ); Tue, 1 Jul 2003 13:40:49 -0400 To: linux-kernel@vger.kernel.org From: "H. Peter Anvin" Subject: Re: [RFC] block layer support for DMA IOMMU bypass mode Date: 1 Jul 2003 10:54:31 -0700 Organization: Transmeta Corporation, Santa Clara CA Message-ID: References: <1057077975.2135.54.camel@mulgrave> <20030701190938.2332f0a8.ak@suse.de> <1057080529.2003.62.camel@mulgrave> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT Disclaimer: Not speaking for Transmeta in any way, shape, or form. Copyright: Copyright 2003 H. Peter Anvin - All Rights Reserved Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Followup to: <1057080529.2003.62.camel@mulgrave> By author: James Bottomley In newsgroup: linux.dev.kernel > > The name was simply to be consistent with BIO_VMERGE_BOUNDARY which is > another asm/io.h setting for this. > > Could you elaborate more on the amd64 IOMMU window. Is this a window > where IOMMU mapping always takes place? > It's a window (in the form of a BAR - base and mask) within which IOMMU mapping always takes place. Outside the window everything is bypass. This applies to all x86-64 machines and some i386 machines, in particular those i386 chipsets with "full GART" support as opposed to "AGP only GART" (my terminology.) Andi likes to say this isn't a real IOMMU (mostly because it doesn't solve the legacy region problem), but I disagree with that view. It still would be nicer if it covered more address space, though. I don't know if it would be worthwhile to support "full GART" on the i386 systems which support it. -hpa -- at work, in private! "Unix gives you enough rope to shoot yourself in the foot." Architectures needed: ia64 m68k mips64 ppc ppc64 s390 s390x sh v850 x86-64