The change makes the user and kernel address spaces on i386
independent, giving each almost the full 4G of usable virtual addresses
except for one PDE at top used for trampoline and per-CPU trampoline
stacks, and system structures that must be always mapped, namely IDT,
GDT, common TSS and LDT, and process-private TSS and LDT if allocated.

By using 1:1 mapping for the kernel text and data, it appeared
possible to eliminate assembler part of the locore.S which bootstraps
initial page table and KPTmap.  The code is rewritten in C and moved
into the pmap_cold(). The comment in vmparam.h explains the KVA
layout.

There is no PCID mechanism available in protected mode, so each
kernel/user switch forth and back completely flushes the TLB, except
for the trampoline PTD region. The TLB invalidations for userspace
becomes trivial, because IPI handlers switch page tables. On the other
hand, context switches no longer need to reload %cr3.

copyout(9) was rewritten to use vm_fault_quick_hold().  An issue for
new copyout(9) is compatibility with wiring user buffers around sysctl
handlers. This explains two kind of locks for copyout ptes and
accounting of the vslock() calls.  The vm_fault_quick_hold() AKA slow
path, is only tried after the 'fast path' failed, which temporary
changes mapping to the userspace and copies the data to/from small
per-cpu buffer in the trampoline.  If a page fault occurs during the
copy, it is short-circuit by exception.s to not even reach C code.

The change was motivated by the need to implement the Meltdown
mitigation, but instead of KPTI the full split is done.  The i386
architecture already shows the sizing problems, in particular, it is
impossible to link clang and lld with debugging.  I expect that the
issues due to the virtual address space limits would only exaggerate
and the split gives more liveness to the platform.

Tested by: pho
Discussed with:	bde
Sponsored by:	The FreeBSD Foundation
MFC after:	1 month
Differential revision:	https://reviews.freebsd.org/D14633

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

Reported by:	emaste
X-MFC-with:	r322347

Introduce a new define to take int account the xAPIC ID limit, for
systems where x2APIC is not available/reliable.

Also change some of the usages of the APIC ID to use an unsigned int
(which is the correct storage type to deal with x2APIC IDs as found in
x2APIC MADT entries).

This allows booting FreeBSD on a box with 256 CPUs and APIC IDs up to
295:

FreeBSD/SMP: Multiprocessor System Detected: 256 CPUs
FreeBSD/SMP: 1 package(s) x 64 core(s) x 4 hardware threads
Package HW ID = 0
	Core HW ID = 0
		CPU0 (BSP): APIC ID: 0
		CPU1 (AP/HT): APIC ID: 1
		CPU2 (AP/HT): APIC ID: 2
		CPU3 (AP/HT): APIC ID: 3
[...]
	Core HW ID = 73
		CPU252 (AP): APIC ID: 292
		CPU253 (AP/HT): APIC ID: 293
		CPU254 (AP/HT): APIC ID: 294
		CPU255 (AP/HT): APIC ID: 295

Submitted by:		kib (previous version)
Relnotes:		yes
MFC after:		1 month
Reviewed by:		kib
Differential revision:	https://reviews.freebsd.org/D11913

Populate the lapics arrays and call cpu_add/lapic_create in the setup
phase instead. Also store the max APIC ID found in the newly
introduced max_apic_id global variable.

This is a requirement in order to make the static arrays currently
using MAX_LAPIC_ID dynamic.

Sponsored by:		Citrix Systems R&D
MFC after:		1 month
Reviewed by:		kib
Differential revision:	https://reviews.freebsd.org/D11911

I thank all developers and contributors for pc98.

Relnotes:	yes

Replace archaic "busses" with modern form "buses."

Intentionally excluded:
* Old/random drivers I didn't recognize
  * Old hardware in general
* Use of "busses" in code as identifiers

No functional change.

http://grammarist.com/spelling/buses-busses/

PR:		216099
Reported by:	bltsrc at mail.ru
Sponsored by:	Dell EMC Isilon

^/user/gjb/hacking since this is likely to be merged to head/ soon.

Sponsored by:	The FreeBSD Foundation

inclusion of (at least) arm builds with the release.

Sponsored by:	The FreeBSD Foundation

all the structures.  While here, move a helper struct only used in
the kernel parser out of this header since it is not part of the MP
specification itself.

apicvar.h to apicreg.h.

Submitted by:	gcooper (partially)
Pointy hat to:	jhb

resource allocation on x86 platforms:
- Add a new helper API that Host-PCI bridge drivers can use to restrict
  resource allocation requests to a set of address ranges for different
  resource types.
- For the ACPI Host-PCI bridge driver, use Producer address range resources
  in _CRS to enumerate valid address ranges for a given Host-PCI bridge.
  This can be disabled by including "hostres" in the debug.acpi.disabled
  tunable.
- For the MPTable Host-PCI bridge driver, use entries in the extended
  MPTable to determine the valid address ranges for a given Host-PCI
  bridge.  This required adding code to parse extended table entries.

Similar to the new PCI-PCI bridge driver, these changes are only enabled
if the NEW_PCIB kernel option is enabled (which is enabled by default on
amd64 and i386).

Approved by:	re (kib)

Sponsored by:	Sandvine Incorporated
MFC after:	14 days

- Register APIC enumerators at SI_SUB_TUNABLES - 1 instead of SI_SUB_CPU - 1.
- Probe CPUs at SI_SUB_TUNABLES - 1.  This allows i386 to set a truly
  accurate mp_maxid value rather than always setting it to MAXCPU - 1.

Sponsored by:	Sandvine Incorporated
Discussed with:	jhb

by /etc/rc.d/jail.

performance in Xen's HVM mode.

  In keeping with style(9)'s recommendations on macros, use a ';'
  after each SYSINIT() macro invocation.  This makes a number of
  lightweight C parsers much happier with the FreeBSD kernel
  source, including cflow's prcc and lxr.

  Discussed with: imp, rink

The requirement to place a ; after each SYSINIT definition has not been
MFC'd, as this might break the compile third-party modules, but merging
the actual ; additions reduces diffs against 8.x making it easier to
merge other changes.

after each SYSINIT() macro invocation.  This makes a number of
lightweight C parsers much happier with the FreeBSD kernel
source, including cflow's prcc and lxr.

MFC after:	1 month
Discussed with:	imp, rink

an APIC ID of 38 for its second CPU):
- Add a new MAX_APIC_ID constant for the highest valid APIC ID for modern
  systems.
- Size the various arrays in the MADT, MP Table, and SMP code that are
  indexed by APIC IDs to allow for up to MAX_APIC_ID.
- Explicitly go through and assign logical cpu ids to local APICs before
  starting any of the APs up rather than doing it while starting up the
  APs.  This step is now where we honor MAXCPU.

MFC after:	1 week

printf.  Otherwise, printfs inside of lapic_init() (such as during a
verbose boot) can uglify the output.

APICs to lapic_init() and ioapic_create().

- Prefer '_' to ' ', as it results in more easily parsed results in
  memory monitoring tools such as vmstat.

- Remove punctuation that is incompatible with using memory type names
  as file names, such as '/' characters.

- Disambiguate some collisions by adding subsystem prefixes to some
  memory types.

- Generally prefer lower case to upper case.

- If the same type is defined in multiple architecture directories,
  attempt to use the same name in additional cases.

Not all instances were caught in this change, so more work is required to
finish this conversion.  Similar changes are required for UMA zone names.

when using an APIC.  This simplifies the APIC code somewhat and also allows
us to be pedantically more compliant with ACPI which mandates no use of
mixed mode.

Found by:	src/tools/tools/kernxref

interrupts that have a trigger mode of conforming.  This fixes problems on
some older machines that still route PCI devices via ISA interrupts when
using an I/O APIC.

Tested by:	Peter Trifonov pvtrifonov at mail dot ru
MFC after:	1 month

interrupt is wired up to all the I/O APICs in the system.  If the system
has only one I/O APIC, then just act as if the entry specified that APIC.
We still don't try to handle global entries in a system with multiple I/O
APICs.

Tested by:	Peter Trifonov pvtrifonov at mail dot ru
MFC after:	1 week

- Fix the MP Table pci bridge drivers to not probe the configuration table
  unless we actually have one.  Machines using a default configuration do
  not have such a table.
- Only allow default configuration types of 5 (ISA + PCI) and 6 (EISA +
  PCI) as the others are not likely to work.  Types 1 through 4 use an
  external APIC (probably with 80486 processors) which we certainly do not
  support, and type 7 uses an MCA bus which has not been tested with the
  new MP Table code.
- Correct the fact that the single I/O APIC in a default configuration has
  an ID of 2, not 0.
- Fix off by one errors in setting the bus types from the default_data[]
  arrays for default configurations.
- Explicitly configure each of the 16 interrupt pins on the sole I/O APIC
  when using a default configuration.  This is especially helpful for type
  6 (EISA + PCI) since the EISA interrupts need to have their polarity
  programmed based on the values in the ELCR.

Much thanks to the submitter and tester who endured several rounds of
testing to get this fixed.

MFC after:	1 week
Tested by:	Georg Schwarz georg dot schwarz at freenet dot de

for the same PCI interrupt.

Tested by:	Pavel Gubin pg at ie dot tusur dot ru
MFC after:	3 days

cut down on the clutter including PCI interrupt routing, MTRR, pcibios,
etc.

Discussed with:	USENIX Cabal

- Allow ioapic_set_{nmi,smi,extint}() to be called multiple times on the
  same pin so long as the pin's mode is the same as the mode being
  requested.
- Add a notion of bus type for the interrupt associated with interrupt pin.
  This is needed so that we can force all EISA interrupts to be active high
  in the forthcoming ioapic_config_intr().
- Fix a bug for EISA systems that didn't remap IRQs.  This would have broken
  EISA systems that tried to disable mixed mode for IRQ 0.

polarity rather than assuming that level triggered IRQs use active low and
edge triggered IRQs use active high.  Both the MultiProcessor 1.4
and ACPI 2.0 Specifications state in their examples that level triggered
EISA IRQs are active low, but in practice they seem to be active high.

Reported by:	Nik Azim Azam nskyline_r35 at yahoo dot com

- Require the APIC enumerators to explicitly enable mixed mode by calling
  ioapic_enable_mixed_mode().  Calling this function tells the apic driver
  that the PC-AT 8259A PICs are present and routable through the first I/O
  APIC via an ExtINT pin.  The mptable enumerator always calls this
  function for now.  The MADT enumerator only enables mixed mode if the
  PC-AT compatability flag is set in the MADT header.
- Allow mixed mode to be enabled or disabled via a 'hw.apic.mixed_mode'
  tunable.  By default this tunable is set to 1 (true).  The kernel option
  NO_MIXED_MODE changes the default to 0 to preserve existing behavior, but
  adding 'hw.apic.mixed_mode=0' to loader.conf achieves the same effect.
- Only use mixed mode to route IRQ 0 if it is both enabled by the APIC
  enumerator and activated by the loader tunable.  Note that both
  conditions must be true, so if the APIC enumerator does not enable mixed
  mode, then you can't set the tunable to try to override the enumerator.