linux-kernel - Re: DMA error when sg->offset value is greater than PAGE

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Date:   Mon, 25 Sep 2017 18:46:19 +0000
From:   Casey Leedom <leedom@...lsio.com>
To:     "Raj, Ashok" <ashok.raj@...el.com>
CC:     Robin Murphy <robin.murphy@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "Harsh Jain" <Harsh@...lsio.com>,
        "David Woodhouse" <David.Woodhouse@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        Dan Williams <dan.j.williams@...el.com>,
        "dwmw2@...radead.org" <dwmw2@...radead.org>
Subject: Re: DMA error when sg->offset value is greater than PAGE_SIZE in
 Intel IOMMU

| From: Raj, Ashok <ashok.raj@...el.com>
| Sent: Monday, September 25, 2017 8:54 AM
|
| Not sure how the page->offset would end up being greater than page-size?
|
| If you have additional traces, please send them by.
|
| Is this a new driver? wondering how we didn't run into this?

  According to Herbert Xu and one of our own engineers, it's actually legal
for Scatter/Gather Lists to have this.  This isn't my area of expertise
though so I'm just passing that on.

  I've asked our team to produce a detailed trace of the exact
Scatter/Gather Lists they're seeing and what ends up coming out of the DMA
Mappings, etc.  They're in India, so I expect that they'll have this for you
by tomorrow morning.

Casey