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SubjectRe: DMA error when sg->offset value is greater than PAGE_SIZE in Intel IOMMU
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Hey Raj,

Let us know if you need help in gathering more debugging information. For
the time being we've decided to ERRATA the use of the Intel I/O MMU with
IPsec till we Root Cause the issue. But this is still at the top of Harsh's
bug list.

With Robin's comments, I'm almost sure that the:

(iov_pfn + sg->offset) << VTD_PAGE_SHIFT)

in your suggested patch is an issue. iov_pfn is a Page Frame Number and
sg->offset is a Byte Offset. It feels like this should be:

size_t page_off = sg->offset & ~VTD_PAGE_MASK;
unsigned long pfn_off = sg->offset >> VTD_PAGE_MASK;
...
sg->dma_address = ((dma_addr_t)
(iov_pfn + pfn_off) << VTD_PAGE_SHIFT) + page_off;

When Harsh tried your original patch, Harsh' test system wouldn't even boot.

Casey

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