MFC r330349 and r330362:

Allow pause_sbt() to catch signals during sleep by passing C_CATCH flag.
Define pause_sig() function macro helper similarly to other kernel functions
which catch signals. Update outdated function description.

Document pause_sig(9) and update prototypes for existing pause(9) and
pause_sbt(9) functions.

Discussed with: kib@
Suggested by: cem@
Sponsored by: Mellanox Technologies

MFC r303151:
Provide counter_warning(9) KPI.

MFC r303155:
Hide counted_warning(9) under #ifdef _KERNEL braces.

MFC r288446: Disable suspend during shutdown.

MFC r279433 (by rstone): Implement asprintf in libkern

MFC r283600:
Perform SU cleanup in the AST handler. Do not sleep waiting for SU cleanup
while owning vnode lock.

On MFC, for KBI stability, td_su member was moved to the end of the
struct thread.

MFC r281915:
Make vpanic() externally visible.

MFC r281916:
Fix DTrace's panic() action.

MFC 278474,278476,280279:
Expand the bitcount*() API and use it to implement CPU_COUNT for cpusets.

278474:
Use __builtin_popcnt() to implement a BIT_COUNT() operation for bitsets and
use this to implement CPU_COUNT() to count the number of CPUs in a cpuset.

278476:
Use __builtin_popcountl() instead of __builtin_popcount().

280279:
Expand the bitcount* API to support 64-bit integers, plain ints and longs
and create a "hidden" API that can be used in other system headers without
adding namespace pollution.
- If the POPCNT instruction is enabled at compile time, use
__builtin_popcount*() to implement __bitcount*(), otherwise fall back
to software implementations.
- Use the existing bitcount16() and bitcount32() from <sys/systm.h> to
implement the non-POPCNT __bitcount16() and __bitcount32() in
<sys/types.h>.
- For the non-POPCNT __bitcount64(), use a similar SWAR method on 64-bit
systems. For 32-bit systems, use two __bitcount32() operations on the
two halves.
- Use __bitcount32() to provide a __bitcount() that operates on plain ints.
- Use either __bitcount32() or __bitcount64() to provide a
__bitcountl() that operates on longs.
- Add public bitcount*() wrappers for __bitcount*() for use in the kernel
in <sys/libkern.h>.
- Use __bitcountl() instead of __builtin_popcountl() in BIT_COUNT().

MFC 276724:
On some Intel CPUs with a P-state but not C-state invariant TSC the TSC
may also halt in C2 and not just C3 (it seems that in some cases the BIOS
advertises its C3 state as a C2 state in _CST). Just play it safe and
disable both C2 and C3 states if a user forces the use of the TSC as the
timecounter on such CPUs.

PR: 192316

MFC 273800:
Rework virtual machine hypervisor detection.
- Move the existing code to x86/x86/identcpu.c since it is x86-specific.
- If the CPUID2_HV flag is set, assume a hypervisor is present and query
the 0x40000000 leaf to determine the hypervisor vendor ID. Export the
vendor ID and the highest supported hypervisor CPUID leaf via
hv_vendor[] and hv_high variables, respectively. The hv_vendor[]
array is also exported via the hw.hv_vendor sysctl.
- Merge the VMWare detection code from tsc.c into the new probe in
identcpu.c. Add a VM_GUEST_VMWARE to identify vmware and use that in
the TSC code to identify VMWare.

Merge the fueword(9) and casueword(9). In particular,

MFC r273783:
Add fueword(9) and casueword(9) functions.
MFC note: ia64 is handled like arm, with NO_FUEWORD define.

MFC r273784:
Replace some calls to fuword() by fueword() with proper error checking.

MFC r273785:
Convert kern_umtx.c to use fueword() and casueword().
MFC note: the sys__umtx_lock and sys__umtx_unlock syscalls are not
converted, they are removed from HEAD, and not used. The do_sem2*()
family is not yet merged to stable/10, corresponding chunk will be
merged after do_sem2* are committed.

MFC r273788 (by jkim):
Actually install casuword(9) to fix build.

MFC r273911:
Add type qualifier volatile to the base (userspace) address argument
of fuword(9) and suword(9).

MFC r272536:
Add kernel option KSTACK_USAGE_PROF.

MFC 264019, 264041, 264048, 264049, 264050, 264051

Add support for event timers whose clock frequency can change while running.

Apparently all ARM configs build kern_et.c, but only a few of them also
build kern_clocksource.c, un-break the build by not referencing functions in
kern_clocksource if NO_EVENTTIMERS is defined.

Add variable-frequency support to the arm mpcore eventtimer driver.

mpcore_timer: Disable the timer and clear any pending bit, then setup the
new counter register values, then restart the timer. Also re-nest the parens
properly for casting the result of converting time and frequency to a count.

MFC r261786, r261789

Rework the EARLY_PRINTF mechanism. Instead of defining a special eprintf()
routine, now a platform can provide a pointer to an early_putc() routine
which is used instead of cn_putc(). Control can be handed off from early
printf support to standard console support by NULLing out the pointer
during standard console init.

Convert two while(1); statements into proper panics.

MFC r261038, r261039, r261040, r261041

Implement generic support for early printf.

Merge r257996,r258001,r258069 from head: fixes for HyperV guest.

- Set description string for VM_GUEST_HV (HyperV guest).
- Add a brief comment about VM_GUEST and vm_guest_sysctl_names relationship.
- CTASSERT that vm_guest range is covered by vm_guest_sysctl_names.

Approved by: re (glebius)

MFC r256502:
Similar to debug.iosize_max_clamp sysctl, introduce
devfs_iosize_max_clamp sysctl, which allows/disables SSIZE_MAX-sized
i/o requests on the devfs files.

Approved by: re (glebius)

MFC r256425:

Centralize the detection logic for the Hyper-V hypervisor.

Submitted by: Roger Pau Monné
Sponsored by: Citrix Systems R&D
Reviewed by: gibbs, grehan
Approved by: re (gjb)

sys/sys/systm.h:
* Add a new VM_GUEST type, VM_GUEST_HV (HyperV guest).

sys/dev/hyperv/vmbus/hv_vmbus_drv_freebsd.c:
sys/dev/hyperv/vmbus/hv_hv.c:
sys/dev/hyperv/stordisengage/hv_ata_pci_disengage.c:
* Set vm_guest to VM_GUEST_HV and use that on other HyperV related
devices instead of cloning the cpuid hypervisor check.
* Cleanup the vmbus_identify function.
------------------------------------------------------------------------

MFC r283600:
Perform SU cleanup in the AST handler. Do not sleep waiting for SU cleanup
while owning vnode lock.

On MFC, for KBI stability, td_su member was moved to the end of the
struct thread.

MFC r281915:
Make vpanic() externally visible.

MFC r281916:
Fix DTrace's panic() action.

MFC 278474,278476,280279:
Expand the bitcount*() API and use it to implement CPU_COUNT for cpusets.

278474:
Use __builtin_popcnt() to implement a BIT_COUNT() operation for bitsets and
use this to implement CPU_COUNT() to count the number of CPUs in a cpuset.

278476:
Use __builtin_popcountl() instead of __builtin_popcount().

280279:
Expand the bitcount* API to support 64-bit integers, plain ints and longs
and create a "hidden" API that can be used in other system headers without
adding namespace pollution.
- If the POPCNT instruction is enabled at compile time, use
__builtin_popcount*() to implement __bitcount*(), otherwise fall back
to software implementations.
- Use the existing bitcount16() and bitcount32() from <sys/systm.h> to
implement the non-POPCNT __bitcount16() and __bitcount32() in
<sys/types.h>.
- For the non-POPCNT __bitcount64(), use a similar SWAR method on 64-bit
systems. For 32-bit systems, use two __bitcount32() operations on the
two halves.
- Use __bitcount32() to provide a __bitcount() that operates on plain ints.
- Use either __bitcount32() or __bitcount64() to provide a
__bitcountl() that operates on longs.
- Add public bitcount*() wrappers for __bitcount*() for use in the kernel
in <sys/libkern.h>.
- Use __bitcountl() instead of __builtin_popcountl() in BIT_COUNT().

MFC 276724:
On some Intel CPUs with a P-state but not C-state invariant TSC the TSC
may also halt in C2 and not just C3 (it seems that in some cases the BIOS
advertises its C3 state as a C2 state in _CST). Just play it safe and
disable both C2 and C3 states if a user forces the use of the TSC as the
timecounter on such CPUs.

PR: 192316

MFC 273800:
Rework virtual machine hypervisor detection.
- Move the existing code to x86/x86/identcpu.c since it is x86-specific.
- If the CPUID2_HV flag is set, assume a hypervisor is present and query
the 0x40000000 leaf to determine the hypervisor vendor ID. Export the
vendor ID and the highest supported hypervisor CPUID leaf via
hv_vendor[] and hv_high variables, respectively. The hv_vendor[]
array is also exported via the hw.hv_vendor sysctl.
- Merge the VMWare detection code from tsc.c into the new probe in
identcpu.c. Add a VM_GUEST_VMWARE to identify vmware and use that in
the TSC code to identify VMWare.

Merge the fueword(9) and casueword(9). In particular,

MFC r273783:
Add fueword(9) and casueword(9) functions.
MFC note: ia64 is handled like arm, with NO_FUEWORD define.

MFC r273784:
Replace some calls to fuword() by fueword() with proper error checking.

MFC r273785:
Convert kern_umtx.c to use fueword() and casueword().
MFC note: the sys__umtx_lock and sys__umtx_unlock syscalls are not
converted, they are removed from HEAD, and not used. The do_sem2*()
family is not yet merged to stable/10, corresponding chunk will be
merged after do_sem2* are committed.

MFC r273788 (by jkim):
Actually install casuword(9) to fix build.

MFC r273911:
Add type qualifier volatile to the base (userspace) address argument
of fuword(9) and suword(9).

MFC r272536:
Add kernel option KSTACK_USAGE_PROF.

MFC 264019, 264041, 264048, 264049, 264050, 264051

Add support for event timers whose clock frequency can change while running.

Apparently all ARM configs build kern_et.c, but only a few of them also
build kern_clocksource.c, un-break the build by not referencing functions in
kern_clocksource if NO_EVENTTIMERS is defined.

Add variable-frequency support to the arm mpcore eventtimer driver.

mpcore_timer: Disable the timer and clear any pending bit, then setup the
new counter register values, then restart the timer. Also re-nest the parens
properly for casting the result of converting time and frequency to a count.

MFC r261786, r261789

Rework the EARLY_PRINTF mechanism. Instead of defining a special eprintf()
routine, now a platform can provide a pointer to an early_putc() routine
which is used instead of cn_putc(). Control can be handed off from early
printf support to standard console support by NULLing out the pointer
during standard console init.

Convert two while(1); statements into proper panics.

MFC r261038, r261039, r261040, r261041

Implement generic support for early printf.

Merge r257996,r258001,r258069 from head: fixes for HyperV guest.

- Set description string for VM_GUEST_HV (HyperV guest).
- Add a brief comment about VM_GUEST and vm_guest_sysctl_names relationship.
- CTASSERT that vm_guest range is covered by vm_guest_sysctl_names.

Approved by: re (glebius)

MFC r256502:
Similar to debug.iosize_max_clamp sysctl, introduce
devfs_iosize_max_clamp sysctl, which allows/disables SSIZE_MAX-sized
i/o requests on the devfs files.

Approved by: re (glebius)

MFC r256425:

Centralize the detection logic for the Hyper-V hypervisor.

Submitted by: Roger Pau Monné
Sponsored by: Citrix Systems R&D
Reviewed by: gibbs, grehan
Approved by: re (gjb)

sys/sys/systm.h:
* Add a new VM_GUEST type, VM_GUEST_HV (HyperV guest).

sys/dev/hyperv/vmbus/hv_vmbus_drv_freebsd.c:
sys/dev/hyperv/vmbus/hv_hv.c:
sys/dev/hyperv/stordisengage/hv_ata_pci_disengage.c:
* Set vm_guest to VM_GUEST_HV and use that on other HyperV related
devices instead of cloning the cpuid hypervisor check.
* Cleanup the vmbus_identify function.
------------------------------------------------------------------------