Re: [Xen-merge] AMD64 dma-mapping

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 24 Jan 2006, at 21:58, Muli Ben-Yehuda wrote:

> > Is there a particular reason that Xen merge doesn't want
> > to use lib/swiotlb.c and instead prefers
> > arch/i386/kernel/swiotlb.c instead?
> Yeah - it's substantially different. I hope the differences can be
> narrowed down and code duplication minimized, possibly with judicious
> use of dma-ops, but that will wait until the merge happens.
I wrote the xen-specific swiotlb (ripped off from arch/ia64), and 
really the only xen-specific part of the swiotlb implementation should 
be that we need to take special care during initialisation that the 
aperture contains contiguous machine memory. Apart from that, I expect 
we need care to distinnguish between phys and machine addresses, but I 
would expect no other differences.
I suspect our best bet is to take lib/swiotlb.c and work out minimal 
changes to get it working on xen, cribbing from xen-specific swiotlb 
where there are particular problems, rather than try and do a full 
merge of the two swiotlbs. This is because most differences are 
probably insignificant/gratuitous.
If someone who is already very familiar with the dma-mapping interfaces 
wanted to investigate this, that would be super. :-)
 -- Keir


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