Documentation/powerpc: Ultravisor API

Protected Execution Facility (PEF) is an architectural change for
POWER 9 that enables Secure Virtual Machines (SVMs). When enabled,
PEF adds a new higher privileged mode, called Ultravisor mode, to POWER
architecture. Along with the new mode there is new firmware called the
Protected Execution Ultravisor (or Ultravisor for short).

POWER 9 DD2.3 chips (PVR=0x004e1203) or greater will be PEF-capable.

Attached documentation provides an overview of PEF and defines the API
for various interfaces that must be implemented in the Ultravisor
firmware as well as in the KVM Hypervisor.

Based on input from Mike Anderson, Thiago Bauermann, Claudio Carvalho,
Ben Herrenschmidt, Guerney Hunt, Paul Mackerras.

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.ibm.com>
Signed-off-by: Ram Pai <linuxram@linux.ibm.com>
Signed-off-by: Guerney Hunt <gdhh@linux.ibm.com>
Reviewed-by: Claudio Carvalho <cclaudio@linux.ibm.com>
Reviewed-by: Michael Anderson <andmike@linux.ibm.com>
Reviewed-by: Thiago Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Claudio Carvalho <cclaudio@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20190822034838.27876-2-cclaudio@linux.ibm.com