Messages in this thread | | | Date | Thu, 24 Jul 2008 00:10:33 +0200 | From | Joerg Roedel <> | Subject | Re: [PATCH]: PCI: GART iommu alignment fixes [v2] |
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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.
Joerg
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