sys: Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

LinuxKPI: Constantly use _LINUXKPI_ prefix in include guards

MFC after: 1 week
Reviewed by: bz, emaste, hselasky, manu
Differential Revision: https://reviews.freebsd.org/D33562

LinuxKPI: Implement clflush_cache_range()

Required by drm-kmod 5.7

MFC after: 1 week
Reviewed by: hselasky, manu
Differential Revision: https://reviews.freebsd.org/D33289

LinuxKPI: Add clflush argument type conversion wrapper

to reduce amount of source patching in drm-kmod.

MFC after: 1 week
Reviewed by: manu
Differential Revision: https://reviews.freebsd.org/D33288

LinuxKPI: Add more #ifdef VM_MEMATTR_WRITE_COMBINING guards

One of the three uses is already guarded; this guards the remaining ones
to support architectures like riscv that do not provide write-combining,
and is needed to build drm-kmod on riscv.

Reviewed by: hselasky, manu
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D31999

LinuxKPI: Import linux_page.c and some dependent code from drm-kmod

No functional changes intended

Reviewed by: hselasky, manu, markj
MFC after: 2 weeks
Differential revision: https://reviews.freebsd.org/D32167

Make sure the "vm_flags" and "vm_page_prot" fields get set correctly
in the VM area structure in the LinuxKPI when doing mmap() and that
unsupported bits are masked away.

While at it fix some redundant use of parenthesing inside some related
macros.

Found by: KrishnamRaju ErapaRaju <Krishna2@chelsio.com>
MFC after: 1 week
Sponsored by: Mellanox Technologies

Fix the definitions of pgprot_{noncached,writecombine} after r316562.

MFC after: 1 week

All these files need sys/vmmeter.h, but now they got it implicitly
included via sys/pcpu.h.

Fix compilation of LinuxKPI for PowerPC.

Found by: emaste @
MFC after: 1 week
Sponsored by: Mellanox Technologies

Implement proper support for memory map operations in the LinuxKPI,
like open, close and fault using the character device pager.

Some notes about the implementation:

1) Linux drivers set the vm_ops and vm_private_data fields during a
mmap() call to indicate that the driver wants to use the LinuxKPI VM
operations. Else these operations are not used.

2) The vm_private_data pointer is associated with a VM area structure
and inserted into an internal LinuxKPI list. If the vm_private_data
pointer already exists, the existing VM area structure is used instead
of the allocated one which gets freed.

3) The LinuxKPI's vm_private_data pointer is used as the callback
handle for the FreeBSD VM object. The VM subsystem in FreeBSD has a
similar list to identify equal handles and will only call the
character device pager's close function once.

4) All LinuxKPI VM operations are serialized through the mmap_sem
sempaphore, which is per procedure, which prevents simultaneous access
to the shared VM area structure when receiving page faults.

Obtained from: kmacy @
MFC after: 1 week
Sponsored by: Mellanox Technologies

Implement a series of physical page management related functions in
the LinuxKPI for accessing user-space memory in the kernel.

Add functions to hold and wire physical page(s) based on a given range
of user-space virtual addresses.

Add functions to get and put a reference on, wire, hold, mark
accessed, copy and dirty a physical page.

Add new VM related structures and defines as a preparation step for
advancing the memory map capabilities of the LinuxKPI.

Add function to figure out if a virtual address was allocated using
malloc().

Add function to convert a virtual kernel address into its physical
page pointer.

Obtained from: kmacy @
MFC after: 1 week
Sponsored by: Mellanox Technologies

Add more PAGE related defines to the LinuxKPI. Move the definition of
"pgprot_t" to "linux/page.h" similar to what Linux does.

Obtained from: kmacy @
MFC after: 1 week
Sponsored by: Mellanox Technologies

Finish process of moving the LinuxKPI module into the default kernel build.

- Move all files related to the LinuxKPI into sys/compat/linuxkpi and
its subfolders.
- Update sys/conf/files and some Makefiles to use new file locations.
- Added description of COMPAT_LINUXKPI to sys/conf/NOTES which in turn
adds the LinuxKPI to all LINT builds.
- The LinuxKPI can be added to the kernel by setting the
COMPAT_LINUXKPI option. The OFED kernel option no longer builds the
LinuxKPI into the kernel. This was done to keep the build rules for
the LinuxKPI in sys/conf/files simple.
- Extend the LinuxKPI module to include support for USB by moving the
Linux USB compat from usb.ko to linuxkpi.ko.
- Bump the FreeBSD_version.
- A universe kernel build has been done.

Reviewed by: np @ (cxgb and cxgbe related changes only)
Sponsored by: Mellanox Technologies