Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

MFC r239228: Build modules along with the XENHVM kernels.

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Add options NO_ADAPTIVE_SX to the XENHVM kernel configuration, matching
its similar disabling of adaptive mutexes and rwlocks. The existing
comment on why this is the case also applies to sx locks.

MFC after: 3 days
Discussed with: attilio

Derive the XENHVM kernel from GENERIC, adding only the options required
to support PV drivers (such as xenpci), and non-adptive locking (along
with a comment about why).

This change eliminates the synchronisation problem between GENERIC and
XENHVM, which had become severely rotted in HEAD, and in 8-STABLE
included non-production kernel debugging features such as WITNESS.

However, it comes at the cost of enabling devices and options that may
not be present under Xen (such as random ethernet cards). For now, opt
for a simpler kernel configuration file rather than using nooptions/
nodevice to enumerate and eliminate them. This leads to a somewhat
larger XENHVM kernel.

This is an MFC candidate for 8-STABLE before 8.2, in order to provide
a production-worthy XENHVM kernel configuration for amd64.

Discussed with: gibbs, cperciva
Reported by: Piete Brooks <Piete.Brooks at cl.cam.ac.uk>
Sponsored by: DARPA, AFRL
MFC after: 3 days

Remove COMPAT_43TTY from stock kernel configuration files.

COMPAT_43TTY enables the sgtty interface. Even though its exposure has
only been removed in FreeBSD 8.0, it wasn't used by anything in the base
system in FreeBSD 5.x (possibly even 4.x?). On those releases, if your
ports/packages are less than two years old, they will prefer termios
over sgtty.

Provide groundwork for 32-bit binary compatibility on non-x86 platforms,
for upcoming 64-bit PowerPC and MIPS support. This renames the COMPAT_IA32
option to COMPAT_FREEBSD32, removes some IA32-specific code from MI parts
of the kernel and enhances the freebsd32 compatibility code to support
big-endian platforms.

Reviewed by: kib, jhb

Adjust style (following the already existing rules) for the newly
introduced option DEADLKRES.

Reported by: danfe, julian, avg

Add the options DEADLKRES (introducing the deadlock resolver thread) in
the 'debugging' section of any HEAD kernel and enable for the mainstream
ones, excluding the embedded architectures.
It may, of course, enabled on a case-by-case basis.

Sponsored by: Sandvine Incorporated
Requested by: emaste
Discussed with: kib

Move the examples for the 'hints' and 'env' keywords from various GENERIC
kernel configs into NOTES.

Reviewed by: imp

Update the ident for the XENHVM kernel config to match the filename.

MFC after: 1 week

* Completely Remove the option STOP_NMI from the kernel. This option
has proven to have a good effect when entering KDB by using a NMI,
but it completely violates all the good rules about interrupts
disabled while holding a spinlock in other occasions. This can be the
cause of deadlocks on events where a normal IPI_STOP is expected.
* Adds an new IPI called IPI_STOP_HARD on all the supported architectures.
This IPI is responsible for sending a stop message among CPUs using a
privileged channel when disponible. In other cases it just does match a
normal IPI_STOP.
Right now the IPI_STOP_HARD functionality uses a NMI on ia32 and amd64
architectures, while on the other has a normal IPI_STOP effect. It is
responsibility of maintainers to eventually implement an hard stop
when necessary and possible.
* Use the new IPI facility in order to implement a new userend SMP kernel
function called stop_cpus_hard(). That is specular to stop_cpu() but
it does use the privileged channel for the stopping facility.
* Let KDB use the newly introduced function stop_cpus_hard() and leave
stop_cpus() for all the other cases
* Disable interrupts on CPU0 when starting the process of APs suspension.
* Style cleanup and comments adding

This patch should fix the reboot/shutdown deadlocks many users are
constantly reporting on mailing lists.

Please don't forget to update your config file with the STOP_NMI
option removal

Reviewed by: jhb
Tested by: pho, bz, rink
Approved by: re (kib)

- Use "device\t" and "options \t" for consistency.

Disable adaptive mutexes and rwlocks for XENHVM.

Merge in support for Xen HVM on amd64 architecture.

Fix comment.

Pointed out by: Ivan Voras

Add a sample kernel config for Xen HVM.