Re: [RFC] block layer support for DMA IOMMU bypass mode II

Andi Kleen (ak@suse.de)
Wed, 2 Jul 2003 19:19:35 +0200


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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