Re: [PATCH] iommu/vt-d: Fix scatterlist offset handling

From	"Raj, Ashok" <ashok.raj@intel.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] iommu/vt-d: Fix scatterlist offset handling
Date	2017-09-28 20:40 +0200
Message-ID	<uuLT4-42q-21@gated-at.bofh.it> (permalink)
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Hi Robin

thanks.. i have no idea.. i see all the other patches from you :-)
my email has decided to play games with me i suppose :-)

On Thu, Sep 28, 2017 at 05:59:11PM +0100, Robin Murphy wrote:
> I hope our email server hasn't got blacklisted again... Said patch is
> the top of this very thread we're replying on[1] - you were definitely
> on cc :(

        (sg->dma_address + sg->dma_len) ----+
        sg->dma_address ---------+          |
        iov_pfn------+           |          |
                     |           |          |
                     v           v          v
    iova:   a        b        c        d        e        f
            |--------|--------|--------|--------|--------|
                              <...calculated....>
                     [_____mapped______]
    pfn:    0        1        2        3        4        5
            |--------|--------|--------|--------|--------|
                     ^           ^          ^
                     |           |          |
        sg->page ----+           |          |
        sg->offset --------------+          |
        (sg->offset + sg->length) ----------+

The picture seems right. Looking at the code i'm not sure if i understand
it correctly.

pgoff = sg->offset & ~PAGE_MASK;

this gets the offset past the start of page.

sg->dma_address = ((dma_addr_t)iov_pfn << VTD_PAGE_SHIFT) + pgoff;

this would set dma_address at b+off instead of starting at c+off correct?

> 
> Robin
> 
> [1]:https://lists.linuxfoundation.org/pipermail/iommu/2017-September/024371.html

Thread

[PATCH] iommu/vt-d: Fix scatterlist offset handling Robin Murphy <robin.murphy@arm.com> - 2017-09-28 16:20 +0200
  Re: [PATCH] iommu/vt-d: Fix scatterlist offset handling Casey Leedom <leedom@chelsio.com> - 2017-09-28 18:20 +0200
    Re: [PATCH] iommu/vt-d: Fix scatterlist offset handling "Raj, Ashok" <ashok.raj@intel.com> - 2017-09-28 18:30 +0200
      Re: [PATCH] iommu/vt-d: Fix scatterlist offset handling Robin Murphy <robin.murphy@arm.com> - 2017-09-28 19:00 +0200
        Re: [PATCH] iommu/vt-d: Fix scatterlist offset handling "Raj, Ashok" <ashok.raj@intel.com> - 2017-09-28 20:40 +0200
  Re: [PATCH] iommu/vt-d: Fix scatterlist offset handling Harsh Jain <Harsh@chelsio.com> - 2017-09-29 10:20 +0200
    Re: [PATCH] iommu/vt-d: Fix scatterlist offset handling Casey Leedom <leedom@chelsio.com> - 2017-09-29 18:20 +0200

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