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Date: Mon, 1 Dec 2008 13:58:52 +0100 From: Joerg Roedel <joro@...tes.org> To: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp> Cc: tsbogend@...ha.franken.de, linux-kernel@...r.kernel.org, mingo@...e.hu Subject: Re: [PATCH v3] Fix dma_mapping_error for 32bit x86 On Mon, Dec 01, 2008 at 09:01:06PM +0900, FUJITA Tomonori wrote: > On Mon, 1 Dec 2008 12:34:51 +0100 > Joerg Roedel <joro@...tes.org> 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). Ah true, thanks. Anyway, the patch also solved the problem with swiotlb on 64bit. Joerg -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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