Revert r330897:

This was intended to be a non-functional change. It wasn't. The commit
message was thus wrong. In addition it broke arm, and merged crypto
related code.

Revert with prejudice.

This revert skips files touched in r316370 since that commit was since
MFCed. This revert also skips files that require $FreeBSD$ property
changes.

Thank you to those who helped me get out of this mess including but not
limited to gonzo, kevans, rgrimes.

Requested by: gjb (re)

Partial merge of the SPDX changes

These changes are incomplete but are making it difficult
to determine what other changes can/should be merged.

No objections from: pfg

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

amd64: make uiomove_fromphys functional for pages not mapped by the DMAP

Place the code introduced in r268660 into a separate function that can be
called from uiomove_fromphys. Instead of pre-allocating two KVA pages use
vmem_alloc to allocate them on demand when needed. This prevents blocking if
a page fault is taken while physical addresses from outside the DMAP are
used, since the lock is now removed.

Also introduce a safety catch in PHYS_TO_DMAP and DMAP_TO_PHYS.

Sponsored by: Citrix Systems R&D
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D947

amd64/amd64/pmap.c:
- Factor out the code to deal with non DMAP addresses from pmap_copy_pages
and place it in pmap_map_io_transient.
- Change the code to use vmem_alloc instead of a set of pre-allocated
pages.
- Use pmap_qenter and don't pin the thread if there can be page faults.

amd64/amd64/uio_machdep.c:
- Use pmap_map_io_transient in order to correctly deal with physical
addresses not covered by the DMAP.

amd64/include/pmap.h:
- Add the prototypes for the new functions.

amd64/include/vmparam.h:
- Add safety catches to make sure PHYS_TO_DMAP and DMAP_TO_PHYS are only
used with addresses covered by the DMAP.

Delete stray clause 3 (Advertising clause) and renumber while i'm
here.

Approved by: alc@

Put the general logic for being a CPU hog into a new function
should_yield(). Use this in various places. Encapsulate the common
case of check-and-yield into a new function maybe_yield().

Change several checks for a magic number of iterations to use
should_yield() instead.

MFC after: 1 week

Begin all license/copyright comments with /*-

Remove checks for curthread == NULL - it can't happen.

Move TDF_DEADLKTREAT into td_pflags (and rename it accordingly) to avoid
having to acquire sched_lock when manipulating it in lockmgr(), uiomove(),
and uiomove_fromphys().

Reviewed by: jhb

Remove advertising clause from University of California Regent's license,
per letter dated July 22, 1999 and permission from Alan Cox.

Approved by: core, alc@

- Add uiomove_fromphys() implementations to alpha and ia64. These only
differ trivially from amd64.
- Correct a spelling error in a comment.

Introduce uiomove_fromphys(). This is a variant of uiomove() that takes
a collection of physical pages as the source. On amd64 it is implemented
using the direct virtual-to-physical map.