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On 08/08/13 07:59, Josh Zhao wrote:
Hi,
I am reading the arm MM initial code, there are 2 questions
I can't understand:
1) Both init_xenheap_pages() and init_domheap_pages() will
invoke init_heap_pages() to initialize pages management. But
there is no flag to know those pages are belonged to xenheap
or domheap. Are xenhelp and domheap in the same zone?
xenheap pages have permanent mappings in the Xen virtual address
space, so they can be accessed from anywhere in the code. domheap
pages by default do not have mappings, and must be explicitly mapped
to be used.
For PV guests, Xen hand most of the virtual address space to the
guest, so only the really critical memory can have permanent
mappings.
2) What's the vmap.c used for ? I saw that only the ioremap
will use it. If so, it seems no needs to allocate pages to
fill the all VMAP range (256M - 1G) by alloc_domheap_page().
The domheap pages allocated here are also for tracking purposes, and
are far fewer than the entire VMAP range.
~Andrew
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