Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Add SMP support to the ARM PLATFORM code. This will allow us to have
different methods to start the secondary cores in a kernel built for
multiple SoCs, e.g. with the Allwinner A20 and A31.

Sponsored by: ABT systems Ltd
Differential Revision: https://reviews.freebsd.org/D5466

Almost all copies of platform_mp_init_secondary just called
intr_pic_init_secondary. Replace them with a direct call. On BCM2836
and ARMADA XP we need to add this function, but it can be empty.

Reviewed by: ian, imp
Sponsored by: ABT Systems Ltd
Differential Revision: https://reviews.freebsd.org/D5460

Remove platform_mp_probe as it's almost identical on most ARM SoCs, and
slightly wrong on the others. We should just check if mp_ncpus is set to
more than one CPU as we may wish to run on a single core even when SMP is
available.

Reviewed by: ian
Sponsored by: ABT Systems Ltd
Differential Revision: https://reviews.freebsd.org/D5458

Fix a mistake that crept in when moving between git and svn, pic_ipi_send
should not be called from platform_mp_init_secondary.

Sponsored by: ABT Systems Ltd

Remove platform_ipi_send, it's an unneeded as all implementations are
identical.

Sponsored by: ABT Systems Ltd

[intrng] Migrate the intrng code from sys/arm/arm to sys/kern/subr_intr.c.

The ci20 port (by kan@) is going to reuse almost all of the intrng code
since the SoC in question looks suspiciously like someone took an ARM
SoC design and replaced the ARM core with a MIPS core.

* migrate out the code;
* rename ARM_ -> INTR_;
* rename arm_ -> intr_;
* move the interrupt flush routine from intr.c / intrng.c into
arm/machdep_intr.c - removing the code duplication and removing
the ARM specific bits from here.

Thanks to the Star Wars: The Force Awakens premiere line for allowing
me a couple hours of quiet time to finish the universe builds.

Tested:

* make universe

TODO:

* The structure definitions in subr_intr.c still includes machine/intr.h
which requires one duplicates all of the intrng definitions in
the platform code (which kan has done, and I think we don't have to.)

Instead I should break out the generic things (function declarations,
common intr structures, etc) into a separate header.

* Kan has requested I make the PIC based IPI stuff optional.

Fix typo (s/ncpus/mp_ncpus/)

Reported by: bz

Since r289279 bufinit() uses mp_ncpus, but some architectures set this
variable during mp_start() which is too late. Move this to mp_setmaxid()
where other architectures set it and move x86 assertions to MI code.

Reviewed by: kib (x86 part)

Rename arm_init_secondary_ic() -> arm_pic_init_secondary(). The latter is
the name the function will have when the new ARM_INTRNG code is integrated,
and doing this rename first will make it easier to toggle the new interrupt
handling code on/off with a config option for debugging.

Enable SMP on the qemu virt platform. We use the device tree to find which
cpus to enable, and PSCI to start them.