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Re: Guest-visible phys2mach part of Xen arch-neutral API? was: [Xen-devel] Uses of &frame_table[xfn]




On 29 Dec 2005, at 16:12, Magenheimer, Dan (HP Labs Fort Collins) wrote:

Note that the current physical=machine in domain0 is not a
design requirement, just the current implementation.  The question
at hand isn't whether Xen/ia64 domain0 should be mapped
physical=machine,
but -- if it is not -- whether the mapping should be guest-visible.

The mapping will need to be guest-visible to allow correct programming of DMA engines. It works okay for you right now because dom0 has p==m. But if that is no longer the case then drivers will break, and you won't be able to implement driver domains either.

Even if you don't go with an explicit p2m table, you'll need a hypercall for getting the same info (which would also be a hook point for maintaining IOMMU mappings, if the architecture needs such a thing and the IOMMU is managed by Xen).

 -- Keir


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