Make NetBSD/sparc64 run on sun4v-based systems.


Currently (as of 2023-10-10) the kernel boots fine using a single CPU (ignoring any additional available CPUs).
The only two systems known to boot the kernel so far are T2000 (T1 CPU) and S7-2 (S7 CPU).
* On T2000 the initial userland process (init) crashes after returning from a system call (access()) where an instruction MMU trap causes the register window to be incorrectly filled.
* On S7-S the intial userland process (init) runs fine and starts the installation program (sysinst), but hangs during the extraction of the sets.


On real hardware


Create an install disc from the official ISO image and issue a 'boot cdrom' command from OpenBoot,


If the sun4v system has more than one logical domain configured, a secondary logical domain can use the 'miniroot' image as a virtual disk to boot from.
Configuration of secondary virtual domain can be done by running e.g. Solaris 11.3/11.4 or OpenBSD as the primary logical domain.
Oracle documentation for the logical domain is here: https://docs.oracle.com/en/virtualization/oracle-vm-server-sparc/index.html
OpenBSD has some notes on using the logical domain feature here: https://undeadly.org/cgi?action=article;sid=20121214153413 and https://flak.tedunangst.com/post/OpenBSD-on-a-Sun-T5120


Setup a boot environment with TFTP, DHCP and NFS as described in https://www.netbsd.org/docs/network/netboot/.
Note that the instruction might be a bit outdated, so some notes are present here: https://mail-index.netbsd.org/netbsd-docs/2020/10/29/msg000560.html and https://mail-index.netbsd.org/netbsd-docs/2020/10/31/msg000561.html.
The root filesystem served by the NFS server can be populated by extracting the sets from the sparc64/binary/sets directory.
Issue a 'boot net:dhcp' command to boot from the network.

On emulated hardware


Can be used for basic verification of the kernel.
Information is available here: https://wiki.qemu.org/Documentation/Platforms/SPARC and http://tyom.blogspot.com/search?q=niagara.
Note that the 'niagara' is required machine type.
Use the NetBSD miniroot filesystem to replace the Solaris 10 image from the opensparc distribution https://www.oracle.com/servers/technologies/opensparc-overview.html.