Re: DMA error when sg->offset value is greater than PAGE_SIZE in Intel IOMMU

[Casey Leedom]

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