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

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Date:   Mon, 25 Sep 2017 19:45:31 +0100
From:   David Woodhouse <dwmw2@...radead.org>
To:     Herbert Xu <herbert@...dor.apana.org.au>,
        Harsh Jain <Harsh@...lsio.com>
Cc:     joro@...tes.org, linux-crypto@...r.kernel.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        leedom@...lsio.com
Subject: Re: DMA error when sg->offset value is greater than PAGE_SIZE in
 Intel IOMMU

On Wed, 2017-09-20 at 16:01 +0800, Herbert Xu wrote:
> Harsh Jain <Harsh@...lsio.com> wrote:
> > 
> > While debugging DMA mapping error in chelsio crypto driver we
> observed that when scatter/gather list received by driver has some
> entry with page->offset > 4096 (PAGE_SIZE). It starts giving DMA
> error.  Without IOMMU it works fine.
> 
> This is not a bug.  The network stack can and will feed us such
> SG lists.

Hm? Under what circumstances is the offset permitted to be >
PAGE_SIZE? 
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