Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753277AbYLAOLA (ORCPT ); Mon, 1 Dec 2008 09:11:00 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752082AbYLAOKv (ORCPT ); Mon, 1 Dec 2008 09:10:51 -0500 Received: from sh.osrg.net ([192.16.179.4]:60062 "EHLO sh.osrg.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751578AbYLAOKv (ORCPT ); Mon, 1 Dec 2008 09:10:51 -0500 Date: Mon, 1 Dec 2008 23:10:33 +0900 To: mingo@elte.hu Cc: fujita.tomonori@lab.ntt.co.jp, joro@8bytes.org, tsbogend@alpha.franken.de, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] Fix dma_mapping_error for 32bit x86 From: FUJITA Tomonori In-Reply-To: <20081201125501.GC21534@elte.hu> References: <20081201113451.GA24323@8bytes.org> <20081201210110L.fujita.tomonori@lab.ntt.co.jp> <20081201125501.GC21534@elte.hu> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-Id: <20081201230926Q.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: 4258 Lines: 101 On Mon, 1 Dec 2008 13:55:01 +0100 Ingo Molnar wrote: > > * FUJITA Tomonori wrote: > > > On Mon, 1 Dec 2008 12:34:51 +0100 > > Joerg Roedel wrote: > > > > > On Sat, Nov 29, 2008 at 01:46:27PM +0100, Thomas Bogendoerfer wrote: > > > > Devices like b44 ethernet can't dma from addresses above 1GB. The driver > > > > handles this cases by falling back to GFP_DMA allocation. But for detecting > > > > the problem it needs to get an indication from dma_mapping_error. > > > > The bug is triggered by using a VMSPLIT option of 2G/2G. > > > > > > Looks like your system uses swiotlb as the dma_ops backend. Its the only > > > implementation providing the ops->mapping_error callback and does not > > > use bad_dma_address as the error value. > > > > I think that you misunderstand the problem. > > > > He uses X86_32 so swiotlb should not be used (which is available on > > only X86_64 and IA64 for now). > > > > b44 needs an address under 1GB so it sets device->dma_mask to > > DMA_30BIT_MASK. With VMSPLIT option of 2G/2G, I guess that b44 could > > get addresses above 1GB from the networking subsystem. In such case, > > nommu_map_single returns bad_dma_address properly, but on X86_32, > > dma_mapping_error always returns 0 (success). So b44 wrongly thinks > > that the address is under 1GB. > > > > This patch fixes dma_mapping_error() to check a passed address > > properly (compares it with bad_dma_address). > > > > As I already wrote, the current git needs a patch modified slightly: > > > > http://marc.info/?l=linux-kernel&m=122797163405377&w=2 > > i have i queued up in x86/urgent, see below. As I wrote, just removing #ifdef is better since: 1) Xen people want swiotlb on X86_32. swiotlb uses ops->mapping_error so X86_32 also needs to check ops->mapping_error. 2) Removing #ifdef hack is always good. But this patch fixes the bug and it works for now. And I think that Thomas tested it. So it's fine to commit this patch by me. I'll send a patch to remove the ifdef on the top of this patch after this patch goes into mainline. > > --------------> > From 7b1dedca42ac0d0d0be01e39d8461bb53a2389b3 Mon Sep 17 00:00:00 2001 > From: Thomas Bogendoerfer > Date: Sat, 29 Nov 2008 13:46:27 +0100 > Subject: [PATCH] x86: fix dma_mapping_error for 32bit x86 > > Devices like b44 ethernet can't dma from addresses above 1GB. The driver > handles this cases by falling back to GFP_DMA allocation. But for detecting > the problem it needs to get an indication from dma_mapping_error. > The bug is triggered by using a VMSPLIT option of 2G/2G. > > Signed-off-by: Thomas Bogendoerfer > Acked-by: FUJITA Tomonori > Signed-off-by: Ingo Molnar > --- > arch/x86/include/asm/dma-mapping.h | 6 ++---- > 1 files changed, 2 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/include/asm/dma-mapping.h b/arch/x86/include/asm/dma-mapping.h > index 7f225a4..097794f 100644 > --- a/arch/x86/include/asm/dma-mapping.h > +++ b/arch/x86/include/asm/dma-mapping.h > @@ -71,15 +71,13 @@ static inline struct dma_mapping_ops *get_dma_ops(struct device *dev) > /* Make sure we keep the same behaviour */ > static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr) > { > -#ifdef CONFIG_X86_32 > - return 0; > -#else > +#ifdef CONFIG_X86_64 > struct dma_mapping_ops *ops = get_dma_ops(dev); > if (ops->mapping_error) > return ops->mapping_error(dev, dma_addr); > > - return (dma_addr == bad_dma_address); > #endif > + return (dma_addr == bad_dma_address); > } > > #define dma_alloc_noncoherent(d, s, h, f) dma_alloc_coherent(d, s, h, f) > -- > 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/ -- 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/