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Re: [Xen-devel] Support for AGP aperture as IOMMU in AMD64 mode [2/2]

To: "Langsdorf, Mark" <mark.langsdorf@xxxxxxx>
Subject: Re: [Xen-devel] Support for AGP aperture as IOMMU in AMD64 mode [2/2]
From: Muli Ben-Yehuda <mulix@xxxxxxxxx>
Date: Fri, 20 Jan 2006 04:03:09 +0200
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On Thu, Jan 19, 2006 at 06:10:11PM -0600, Langsdorf, Mark wrote:

> Some of those change are definitely Xen specific, such as the
> switch from virt_to_phys() to virt_to_bus around line 416,

mainline has 

#define virt_to_bus virt_to_phys,

so that should just work. However I'm pretty sure someone was pushing
for deprecating virt_to_bus?

> and the switch from __get_free_pages to alloc_gatt_pages near
> line 740.  Similarly, I had to introduce some hypervisor calls
> to get the true size of memory so that the GART is enabled even
> if dom0 has less than 4 GB of memory.

That could be hidden in an arch specific is_iommu_needed() call that
does the obvious things on bare metal and Xen.

> > The big patch you sent out we also need to go through in some detail. 
> > It's rather bigger than I would have expected. Hopefully 
> > there is some possibility of cleaning up and keeping things closer
> > to the native original source files.
> Most of the big patch is adding 3 mostly unmodified files
> from arch/x86_64/kernel to arch/xen/x86_64/kernel.  The
> rest of the code changes are pretty minor.

Wouldn't making Xen a subarch of x86-64 alleviate the need for copying
these files over? you could then just use the unmodified files. Also,
the dma-ops in 2.6.16-rc1 should make it cleaner as well. I believe
the statement at the summit was that the subarch changes will go in

Muli Ben-Yehuda
http://www.mulix.org | http://mulix.livejournal.com/

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