Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754388AbYKTHwS (ORCPT ); Thu, 20 Nov 2008 02:52:18 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753468AbYKTHwG (ORCPT ); Thu, 20 Nov 2008 02:52:06 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:53949 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753033AbYKTHwF (ORCPT ); Thu, 20 Nov 2008 02:52:05 -0500 Date: Thu, 20 Nov 2008 08:51:39 +0100 From: Ingo Molnar To: FUJITA Tomonori Cc: muli@il.ibm.com, joerg.roedel@amd.com, iommu@lists.linux-foundation.org, mingo@redhat.com, linux-kernel@vger.kernel.org Subject: Re: [GIT PULL] AMD IOMMU updates for 2.6.28-rc5 Message-ID: <20081120075139.GB11930@elte.hu> References: <20081118154322.GX13394@amd.com> <20081119150504G.fujita.tomonori@lab.ntt.co.jp> <20081119125748.GK7113@il.ibm.com> <20081120132545Q.fujita.tomonori@lab.ntt.co.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20081120132545Q.fujita.tomonori@lab.ntt.co.jp> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00,DNS_FROM_SECURITYSAGE autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] 0.0 DNS_FROM_SECURITYSAGE RBL: Envelope sender in blackholes.securitysage.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1557 Lines: 36 * FUJITA Tomonori wrote: > > > It had been the default option for AMD IOMMU until you hit the > > > bugs. IIRC, VT-d also shares a protection domain by default. It > > > would be nice to avoid surprising users if the two > > > virtualization IOMMUs works in the similar way. > > > > Calgary has a per-bus protection domain, both on x86 and PPC. > > I see. Then it might be better to change VT-d to use a separate > protection domain by default. yes, agreed, and that should be the sane default for any IOMMU driver - unless the performance impact is prohibitive. Note that this widens the positive impact of the IOMMU code: not only does it enable transparent support of DMA to/from devices that have a limited DMA range, not only does it help isolation in virtualization - it also acts as a daily debug helper for _native_ drivers. Note that people will prefer to run with an IOMMU enabled even if all devices support the full memory range - just due to the DMA protection features. Just like people prefer to run an OS with paging protections enabled ;-) It also puts pressure on the hw design side to treat IOMMUs not just as some fringe feature for compatibility with older transports or virtualization, but also as a prime-time native IO feature. Ingo -- 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/