Xen devel - Mar 2009 - Dom0 initial memory map guarantees

While for DomU''s the initial memory map clearly cannot be expected to
be
contiguous in MFN space, currently it happens to be that way for (x86)
Dom0 (and even the !NDEBUG case only intentionally breaks this for the
space beyond v_end).

Without a formal guarantee it would seem fragile, however, to rely on
this. Thus the question is whether it''s reasonable to document such a
behavior, or whether instead any such assumption should be forcefully
broken by the Dom0 builder.

Thanks, Jan


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On 30/03/2009 10:10, "Jan Beulich" <jbeulich@novell.com> wrote:
> While for DomU''s the initial memory map clearly cannot be expected
to be
> contiguous in MFN space, currently it happens to be that way for (x86)
> Dom0 (and even the !NDEBUG case only intentionally breaks this for the
> space beyond v_end).
> 
> Without a formal guarantee it would seem fragile, however, to rely on
> this. Thus the question is whether it''s reasonable to document
such a
> behavior, or whether instead any such assumption should be forcefully
> broken by the Dom0 builder.
You can feel free to forcefully break it in debug builds of Xen. We already
do for most of dom0''s allocation, but we don''t bother for the
initial memory
map. That''s just laziness however -- contiguity is not guaranteed.

 -- Keir



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