pvh dom0: construct_dom0 changes

[Xen-changelog] [xen master] pvh dom0: construct_dom0 changes
http://lists.xen.org/archives/html/xen-changelog/2014-05/msg00168.html
PVH対応

This patch changes construct_dom0() to boot in pvh mode:
      - Make sure dom0 elf supports pvh mode.
      - Call guest_physmap_add_page for pvh rather than simple p2m setting
      - Map all non-RAM regions 1:1 upto the end region in e820 or 4GB which
        ever is higher.
      - Allocate p2m, copying calculation from toolstack.
      - Allocate shared info page from the virtual space so that dom0 PT
        can be updated. Then update p2m for it with the actual mfn.
      - Since we build the page tables for pvh same as for pv, in
        pvh_fixup_page_tables_for_hap we replace the mfns with pfns.

Linux 3.14 and PVH
http://blog.xen.org/index.php/2014/01/31/linux-3-14-and-pvh/

It is a hybrid PV - hence the ‘PVH’ name - a PV guest within an HVM container.