Re: FW: [Xen-devel] Xen + other stuff?

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

> Pardon my uninformed newbie question, but why does domain 0 need to map
> another domain into its own address space? Isn't that all in the realm of
> the hypervisor? Isn't the hypervisor the only entity that needs 4G support?
> 
> Shouldn't domain 0 only need to be able to allocate the pages without having
> to map them somewhere in its own space?

Domain 0 is responsible for many 'control' operations, such as
creating and managing other domains. This includes loading the kernel
image for a new domain, for which it needs direct access to the new
domain's memory.

Anyway, to avoid confusion here is what we currently support:
 
 1. Up to 4GB memory in the whole system.
 2. Up to 800MB per Xenolinux instance.

That is, if you have 4GB then all that memory /can/ be used, but
spread across several Xenolinux instances. An individual Xenolinux can
only make use of 800MB.

Despite this, the domain-building tools in domain 0 /can/ access all
4GB of memory. I guess this sounds confusing unless you understand the
underlying implementation. Just go with it :-)

 -- Keir


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