From: David Woodhouse <dwmw2@infradead.org>
To: Robin Murphy <robin.murphy@arm.com>, joro@8bytes.org
Cc: ashok.raj@intel.com, leedom@chelsio.com, Harsh@chelsio.com,
herbert@gondor.apana.org.au, iommu@lists.linux-foundation.org,
linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] iommu/vt-d: Fix scatterlist offset handling
Date: Tue, 03 Oct 2017 23:16:16 +0100 [thread overview]
Message-ID: <1507068976.29211.156.camel@infradead.org> (raw)
In-Reply-To: <db8c70d7-5978-20e8-d29a-91a4312f97dd@arm.com>
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On Tue, 2017-10-03 at 19:05 +0100, Robin Murphy wrote:
>
> Now, there are indeed plenty of drivers and subsystems which do work on
> lists of explicitly single pages - anything doing some variant of
> "addr = kmap_atomic(sg_page(sg)) + sg->offset;" is easy to spot - but I
> don't think DMA API implementations are in a position to make any kind
> of assumption; nearly all of them just shut up and handle sg->length
> bytes from sg_phys(sg) without questioning the caller, and I reckon
> that's exactly what they should be doing.
So what's the point in sg->page in the first place? If even the
*offset* can be greater than page size, it isn't even the *first* page
(as you called it). Why aren't we just using a physical address,
instead of an arbitrary page and an offset from that?
Can we have *negative* sg->offset too? :)
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next prev parent reply other threads:[~2017-10-03 22:16 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-28 14:14 Robin Murphy
2017-09-28 16:17 ` Casey Leedom
2017-09-28 13:29 ` Raj, Ashok
2017-09-28 16:59 ` Robin Murphy
2017-09-28 15:43 ` Raj, Ashok
2017-10-03 19:36 ` Raj, Ashok
2017-09-29 8:14 ` Harsh Jain
2017-09-29 16:18 ` Casey Leedom
[not found] ` <e2c92d3a-3d5d-a0eb-7d5f-a9453e48cfd5@chelsio.com>
2017-10-03 22:22 ` Casey Leedom
2017-10-03 12:55 ` David Woodhouse
2017-10-03 18:05 ` Robin Murphy
2017-10-03 22:16 ` David Woodhouse [this message]
2017-10-04 11:18 ` Robin Murphy
2017-10-06 14:43 ` Joerg Roedel
2017-10-06 12:54 ` Raj, Ashok
2017-11-06 18:47 ` Jacob Pan
2017-11-15 23:54 ` Jacob Pan
2017-11-16 21:32 ` Alex Williamson
2017-11-16 21:09 ` Raj, Ashok
2017-11-17 16:18 ` Alex Williamson
2017-11-17 15:48 ` Raj, Ashok
2017-11-17 17:44 ` Casey Leedom
2017-11-17 18:09 ` Jacob Pan
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