ppc/pnv: add a XIVE interrupt controller model for POWER9

ppc/pnv: add a XIVE interrupt controller model for POWER9

This is a simple model of the POWER9 XIVE interrupt controller for the
PowerNV machine which only addresses the needs of the skiboot
firmware. The PowerNV model reuses the common XIVE framework developed
for sPAPR as the fundamentals aspects are quite the same. The
difference are outlined below.

The controller initial BAR configuration is performed using the XSCOM
bus from there, MMIO are used for further configuration.

The MMIO regions exposed are :

 - Interrupt controller registers
 - ESB pages for IPIs and ENDs
 - Presenter MMIO (Not used)
 - Thread Interrupt Management Area MMIO, direct and indirect

The virtualization controller MMIO region containing the IPI ESB pages
and END ESB pages is sub-divided into "sets" which map portions of the
VC region to the different ESB pages. These are modeled with custom
address spaces and the XiveSource and XiveENDSource objects are sized
to the maximum allowed by HW. The memory regions are resized at
run-time using the configuration of EDT set translation table provided
by the firmware.

The XIVE virtualization structure tables (EAT, ENDT, NVTT) are now in
the machine RAM and not in the hypervisor anymore. The firmware
(skiboot) configures these tables using Virtual Structure Descriptor
defining the characteristics of each table : SBE, EAS, END and
NVT. These are later used to access the virtual interrupt entries. The
internal cache of these tables in the interrupt controller is updated
and invalidated using a set of registers.

Still to address to complete the model but not fully required is the
support for block grouping. Escalation support will be necessary for
KVM guests.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20190306085032.15744-7-clg@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>