From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754098AbYISMeo (ORCPT ); Fri, 19 Sep 2008 08:34:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751287AbYISMeg (ORCPT ); Fri, 19 Sep 2008 08:34:36 -0400 Received: from outbound-wa4.frontbridge.com ([216.32.181.16]:65163 "EHLO WA4EHSOBE002.bigfish.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751263AbYISMeg (ORCPT ); Fri, 19 Sep 2008 08:34:36 -0400 X-BigFish: VPS-51(z21eW5edJz1418M1432R98dR1411M1805M936fQ873fnzz10d3izzz32i6bh43j61h) X-Spam-TCS-SCL: 0:0 X-FB-SS: 5, X-WSS-ID: 0K7G09C-03-H4A-01 Date: Fri, 19 Sep 2008 14:34:26 +0200 From: Joerg Roedel To: FUJITA Tomonori CC: mingo@elte.hu, linux-kernel@vger.kernel.org Subject: Re: [GIT PULL] AMD IOMMU updates for 2.6.28 Message-ID: <20080919123426.GN24392@amd.com> References: <20080919202344V.fujita.tomonori@lab.ntt.co.jp> <20080919204738G.fujita.tomonori@lab.ntt.co.jp> <20080919115259.GL24392@amd.com> <20080919212327Y.fujita.tomonori@lab.ntt.co.jp> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20080919212327Y.fujita.tomonori@lab.ntt.co.jp> User-Agent: mutt-ng/devel-r804 (Linux) X-OriginalArrivalTime: 19 Sep 2008 12:34:26.0707 (UTC) FILETIME=[0DC09630:01C91A54] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Sep 19, 2008 at 09:24:18PM +0900, FUJITA Tomonori wrote: > On Fri, 19 Sep 2008 13:52:59 +0200 > Joerg Roedel wrote: > > > On Fri, Sep 19, 2008 at 08:47:54PM +0900, FUJITA Tomonori wrote: > > > On Fri, 19 Sep 2008 20:23:50 +0900 > > > FUJITA Tomonori wrote: > > > > > > And you don't need to add 'fullflush' to the generic place too. > > > > > > 'fullflush' will be supported with only GART and AMD IOMMU. So adding > > > the description of it to both GART and AMD IOMMU should be fine. > > > > > > 'fullflush' has the same meaning for both IOMMUs. That's nice > > > consistency, I think. > > > > Huh? The whole point of this patch was to have a common option between > > IOMMUs to disable lazy IOTLB flushing. This was suggested by _you_ and > > the only reason I wrote this patch. > > You misunderstand what I meant. I'm sorry if my explanation is not > clear. > > > > After this patch we can change other IOMMU implementations with lazy > > flushing to use that parameter too. > > I'm not sure that Calgary wants to support such option. It always uses > lazy flushing. > > > What I don't like is that there is no consistency about the option > name for lazy flushing. It doesn't mean that we move the option to the > generic place. > > Here's my first reply: > > = > Would it be nice to have consistency of IOMMU parameters? > > VT-d also has the kernel-boot option for this lazy flushing trick > though VT-d 'strict' option is more vague than 'unmap_flush' > = > > What I meant that using the option name 'strict' that VT-d uses for > lazy flushing for AMD IOMMU would be better than introducing a new > option name, "unmap_flush" for AMD IOMMU though I don't think that > 'strict' is the good name. > > > Seems 'fullflush' is better than 'strict'. So I think that it's better > to use 'fullflush' for AMD IMMU rather introducing a new name, > 'unmap_flush'. But again, it doesn't mean that 'fullflush' moves to > the generic place. Ok, so now we have fullflush, which makes sense for all x86 hardware IOMMUs except maybe Calgary (from what I know about Calgary fullflush can be implemented there only with a abyssal performance penalty nobody is willing to pay). So it makes sense to have the option in the generic place. But we can surely add a comment that it does not affect Calgary to the kernel documentation (and change VT-d to use that parameter too). But the AMD IOMMU update chain is not the right place for making big changes to other IOMMUs. Joerg -- | AMD Saxony Limited Liability Company & Co. KG Operating | Wilschdorfer Landstr. 101, 01109 Dresden, Germany System | Register Court Dresden: HRA 4896 Research | General Partner authorized to represent: Center | AMD Saxony LLC (Wilmington, Delaware, US) | General Manager of AMD Saxony LLC: Dr. Hans-R. Deppe, Thomas McCoy