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

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On Wed, Sep 27, 2017 at 9:31 AM, Casey Leedom <leedom@chelsio.com> wrote:
> | From: Dan Williams <dan.j.williams@intel.com>
> | Sent: Tuesday, September 26, 2017 9:10 AM
> |
> | On Tue, Sep 26, 2017 at 9:06 AM, Casey Leedom <leedom@chelsio.com> wrote:
> | > | From: Robin Murphy <robin.murphy@arm.com>
> | > | Sent: Tuesday, September 26, 2017 7:22 AM
> | > |...
> | > ...
> | >   Regardless, it seems that you agree that there's an issue with the Intel
> | > I/O MMU support code with regard to the legal values which a (struct
> | > scatterlist) can take on?  I still can't find any documentation for this
> | > and, personally, I'm a bit baffled by a Page-oriented Scatter/Gather List
> | > representation where [Offset, Offset+Length) can reside outside the Page.
> |
> | Consider the case where the page represents a huge page, then an
> | offset greater than PAGE_SIZE (up to HPAGE_SIZE) makes sense.
>
>   Okay, but whatever the underlaying Page Size is, should [Offset,
> Offset+Length) completely reside within the referenced Page?  I'm just
> trying to understand the Invariance Conditions which are assumed by all of
> the code which processes Scatter/gather Lists ...

As far as I can see "Offset can be greater than PAGE_SIZE" is the only
safe assumption for core code.

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Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Dan Williams <dan.j.williams@intel.com> - 2017-09-26 18:20 +0200
  Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Casey Leedom <leedom@chelsio.com> - 2017-09-27 18:40 +0200
    Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Dan Williams <dan.j.williams@intel.com> - 2017-09-27 19:20 +0200
      Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Christoph Hellwig <hch@infradead.org> - 2017-10-01 11:00 +0200
    Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU "Raj, Ashok" <ashok.raj@intel.com> - 2017-09-27 19:50 +0200
      Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Casey Leedom <leedom@chelsio.com> - 2017-09-27 23:30 +0200
        Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU "Raj, Ashok" <ashok.raj@intel.com> - 2017-09-28 00:10 +0200
          Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Casey Leedom <leedom@chelsio.com> - 2017-09-28 00:20 +0200
            Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Harsh Jain <Harsh@chelsio.com> - 2017-09-28 07:10 +0200
            Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Herbert Xu <herbert@gondor.apana.org.au> - 2017-09-28 12:40 +0200
        Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Harsh Jain <Harsh@chelsio.com> - 2017-09-28 15:40 +0200
          Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU "Raj, Ashok" <ashok.raj@intel.com> - 2017-09-28 18:10 +0200
            Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Harsh Jain <Harsh@chelsio.com> - 2017-09-29 07:40 +0200
  Re: DMA error when sg->offset value is greater than PAGE_SIZE in  Intel IOMMU Casey Leedom <leedom@chelsio.com> - 2017-09-27 19:40 +0200

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