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

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

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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