Date: Wed, 2 Jul 2003 19:19:35 +0200
From: Andi Kleen <ak@suse.de>
To: Grant Grundler <grundler@parisc-linux.org>
Cc: Andi Kleen <ak@suse.de>, "David S. Miller" <davem@redhat.com>,
       James.Bottomley@steeleye.com, axboe@suse.de, suparna@in.ibm.com,
       linux-kernel@vger.kernel.org, alex_williamson@hp.com,
       bjorn_helgaas@hp.com
Subject: Re: [RFC] block layer support for DMA IOMMU bypass mode II
Message-ID: <20030702171935.GA32261@wotan.suse.de>
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On Wed, Jul 02, 2003 at 10:53:33AM -0600, Grant Grundler wrote:
> 
> > Maybe I'm missing something but from James description it sounds like the 
> > block layer assumes that it can pass in a sglist with arbitary elements 
> > and get it back remapped to continuous DMA addresses.
> 
> In the x86-64 case, If the 1k elements are not physically contigous,
> I think most of them would get their own mapping.

Yes, but it won't be continguous in bus space.

> 
> For x86-64, if an entry ends on a 4k alignment and the next one starts
> on a 4k alignment, could those be merged into one DMA segment that uses
> two adjacent mapping entries?

Yes, it is now in the version I wrote last night, but not in the 
previous code that's in the tree.

-Andi
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