Messages in this thread | | | Date | Mon, 1 Dec 2008 20:36:56 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH v3] Fix dma_mapping_error for 32bit x86 |
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* FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote:
> On Mon, 1 Dec 2008 15:35:34 +0100 > Ingo Molnar <mingo@elte.hu> wrote: > > > > > * FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote: > > > > > On Mon, 1 Dec 2008 13:55:01 +0100 > > > Ingo Molnar <mingo@elte.hu> wrote: > > > > > > > > > > > * FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote: > > > > > > > > > On Mon, 1 Dec 2008 12:34:51 +0100 > > > > > Joerg Roedel <joro@8bytes.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). > > > > > > > > > > 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. > > > > yeah, i included the tested patch. > > > > > I'll send a patch to remove the ifdef on the top of this patch after > > > this patch goes into mainline. > > > > sure - or you can send it against tip/master straight away. > > Ok, here you are. > > Note that this is for 2.6.29 (not 2.6.28).
thanks, applied to tip/x86/iommu.
Ingo
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