[PATCH -V5 0/13] arch/powerpc: Add 64TB support to ppc64

Hi,

This patchset include patches for supporting 64TB with ppc64. I haven't booted
this on hardware with 64TB memory yet. But they boot fine on real hardware with
less memory. Changes extend VSID bits to 38 bits for a 256MB segment
and 26 bits for 1TB segments. 

Changes from v4:
 * Drop patch "arch/powerpc: properly offset the context bits for 1T segemnts"
   based on review feedback
 * split CONTEX_BITS related changes from patch 12
 * Add a new doc update patch

Changes from v3:
 * Address review comments.
 * Added new patch to ensure proto-VSID isolation between kernel and user space

Changes from V2:
 * Fix few FIXMEs in the patchset. I have added them as separate patch for
   easier review. That should help us to drop those changes if we don't agree.

Changes from V1:
* Drop the usage of structure (struct virt_addr) to carry virtual address.
  We now represent virtual address via vpn which is virtual address shifted 
  right 12 bits.

Thanks,
-aneesh