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SubjectRe: DMA error when sg->offset value is greater than PAGE_SIZE in Intel IOMMU
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On 28-09-2017 02:59, Casey Leedom wrote:
> 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.
Today I tried with "Intel_iommu=sp_off" boot option. Traffic runs without any error for more than 1 hrs. What magic this option did? :)
>
> Casey

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