From: Casey Leedom <leedom@chelsio.com>
To: Dan Williams <dan.j.williams@intel.com>
CC: Robin Murphy <robin.murphy@arm.com>, "Harsh Jain" <Harsh@chelsio.com>,
        "Raj, Ashok" <ashok.raj@intel.com>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        David Woodhouse <David.Woodhouse@intel.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>,
        "linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>,
        "dwmw2@infradead.org" <dwmw2@infradead.org>,
        Michael Werner <werner@chelsio.com>
Subject: Re: DMA error when sg->offset value is greater than PAGE_SIZE in
 Intel IOMMU
Thread-Topic: DMA error when sg->offset value is greater than PAGE_SIZE in
 Intel IOMMU
Thread-Index: AQHTLrKuCX/YGlya50aETYTEmnILyqK9cAoAgAAkZQCACFcnkv//5CkAgAAvAguAAJgAAIAAj7QAgAAh/4CAABrJ6IAAA2oAgAGW6yY=
Date: Wed, 27 Sep 2017 16:31:04 +0000
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| 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 ...

Casey