Re:[XenPPC] [xenppc-unstable] [TOOLS][POWERPC] Use a smaller page array and place common code in utils.c

[Jimi Xenidis <jimix@xxxxxxxxxxxxxx>]

This changeset will need a little more 'splainin
> # HG changeset patch
> # User Jimi Xenidis <jimix@xxxxxxxxxxxxxx>
> # Node ID 2fcfe6600b1db8ca2ba78a00317f2da6fc2620bf
> # Parent  d408fcf1975a43593d746b2acbe840dbffd911b8
> [TOOLS][POWERPC] Use a smaller page array and place common code in  
> utils.c
On PPC Dom0 Kernel communicates with Xen using something called the  
XenComm.  This is a way for the Kernel to describe all the physical  
frames (not machine frames) the back a potentially large user-level  
data structure.
the list of pages is limited to a Page and therefore can have no more  
than 511 ((PAGE_SIZE/sizeof(u16)) - 1).
If you create DomU with >= 1G memory you end up with:
  pages: 0x40000
  page_array in bytes: pages*8 = 0x200000
  page_array in pages: 0x200000 >> 12: 512
  BANG!

The easy-yet-incomplete fix (as done in this patch)
  - since we only scribble into the RMA we only need to fill the  
page-array with that.
  - since we know the RMA is machine contiguous we only need for xen  
to give us the first page
    and we can figure out the rest.
  - This patch does this.

The right fix, necessary for save and restore, is to teach libxc to  
use the start_pfn member so we can get the page_array by using  
several calls.  I hope to be submitting this patch up-stream today  
and pushing it to xenppc-unstable.hg at the same time.
-JX

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