Re: [XenAccess-devel] What's allocated on top 1M region of domU?

[Bryan D. P. <br...@th...>]

> Though I mean pseudo physical memory, this answer is correct?
> #I know xen is replaced on virtual address space of DomU.

Ahh yes, this is just for the virtual address spaces.  I'm not sure
what you would be seeing at the top of the physical address space,
unless that just happens to be how Xen implements its location in the
domain.  I'd have to poke through the Xen source code to know for
sure...


> Ok. If your answer is what I intended, top 1M region problem is solved.
> But there are some bit regions I can't access. What are they?
> #some regions can't be accessed continuously and some regions can't be
> accessed often.
> #incidentally, I access to domU while it being paused.

It is possible that there are regions of physical memory that you
won't always be able to access.  This is likely very dependent on your
system, but I can imagine you seeing this type of behavior when memory
is swapped to disk, for example.  If you can find the page table
entries associated with these "missing" pieces of memory, you can
check the flags in the PTE and probably learn more about why the
memory is not there.

Just scanning through all physical addresses offers no guarantee that
you will be able to access every page.  This is one reason why it is
usually more useful to access memory via virtual address instead of
physical address.

-bryan


-- 
Bryan D. Payne
Graduate Student, Computer Science
Georgia Tech Information Security Center
http://www.bryanpayne.org