Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755559AbYGWXPs (ORCPT ); Wed, 23 Jul 2008 19:15:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754206AbYGWXPi (ORCPT ); Wed, 23 Jul 2008 19:15:38 -0400 Received: from sh.osrg.net ([192.16.179.4]:52574 "EHLO sh.osrg.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754058AbYGWXPh (ORCPT ); Wed, 23 Jul 2008 19:15:37 -0400 Date: Thu, 24 Jul 2008 08:14:47 +0900 To: joro@8bytes.org Cc: prarit@redhat.com, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, jbarnes@virtuousgeek.org, fujita.tomonori@lab.ntt.co.jp Subject: Re: [PATCH]: PCI: GART iommu alignment fixes [v2] From: FUJITA Tomonori In-Reply-To: <20080723221033.GD13662@8bytes.org> References: <20080723111928.15828.42561.sendpatchset@prarit.bos.redhat.com> <20080723221033.GD13662@8bytes.org> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-Id: <20080724081528F.fujita.tomonori@lab.ntt.co.jp> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1381 Lines: 26 On Thu, 24 Jul 2008 00:10:33 +0200 Joerg Roedel wrote: > On Wed, Jul 23, 2008 at 07:19:43AM -0400, Prarit Bhargava wrote: > > pci_alloc_consistent/dma_alloc_coherent does not return size aligned > > addresses. > > > > >From Documentation/DMA-mapping.txt: > > > > "pci_alloc_consistent returns two values: the virtual address which you > > can use to access it from the CPU and dma_handle which you pass to the > > card. > > > > The cpu return address and the DMA bus master address are both > > guaranteed to be aligned to the smallest PAGE_SIZE order which > > is greater than or equal to the requested size. This invariant > > exists (for example) to guarantee that if you allocate a chunk > > which is smaller than or equal to 64 kilobytes, the extent of the > > buffer you receive will not cross a 64K boundary." > > Interesting. Have you experienced any problems because of that > misbehavior in the GART code? AMD IOMMU currently also violates this > requirement. I will send a patch to fix that there too. IIRC, only PARISC and POWER IOMMUs follow the above rule. So I also wondered what problem he hit. -- 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/