Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758316AbZKYHrW (ORCPT ); Wed, 25 Nov 2009 02:47:22 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753524AbZKYHrW (ORCPT ); Wed, 25 Nov 2009 02:47:22 -0500 Received: from fallback.mail.elte.hu ([157.181.151.13]:35244 "EHLO fallback.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752420AbZKYHrV (ORCPT ); Wed, 25 Nov 2009 02:47:21 -0500 Date: Wed, 25 Nov 2009 08:25:04 +0100 From: Ingo Molnar To: FUJITA Tomonori Cc: yinghai@kernel.org, hpa@zytor.com, tglx@linutronix.de, linux-kernel@vger.kernel.org Subject: Re: [PATCH] x86: fix gart iommu using for amd 64 bit system Message-ID: <20091125072504.GA6568@elte.hu> References: <4B0BB892.9080401@kernel.org> <20091124225000H.fujita.tomonori@lab.ntt.co.jp> <20091124152645.GD21821@elte.hu> <20091125085730S.fujita.tomonori@lab.ntt.co.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20091125085730S.fujita.tomonori@lab.ntt.co.jp> User-Agent: Mutt/1.5.20 (2009-08-17) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.5 -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1310 Lines: 36 * FUJITA Tomonori wrote: > On Tue, 24 Nov 2009 16:26:45 +0100 > Ingo Molnar wrote: > > > > > * FUJITA Tomonori wrote: > > > > > > don't think user will like to use SWIOTLB instead of swiotlb. > > > > > > I doubt that users care about a way to fix their problems. > > > > As far as swiotlb vs. GART goes, arguably a non-bouncing hw based > > solution (GART) is superior to a bouncing one (swiotlb), right? > > Yeah, but GART is not a real IOMMU that always does address > translation. If users want performance, they need 64bit DMA capable > devices to skip GART. With such devices, GART and SWIOTLB are same. > > So this hacky GART workaround is useful for only people who use non > 64bit DMA devices and broken BIOS with GART. IMO, it's not worth > having the workaround. Well, what Yinghai is saying that for that (nonzero) subset of people this change is a regression, and his patch fixes that. We dont do regressions so this needs to be addressed. Thanks, 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/