MFC 321762
hyperv: Add VF bringup scripts and devd rules.

How network VF works with hn(4) on Hyper-V in non-transparent mode:

- Each network VF has a cooresponding hn(4).
- The network VF and the it's cooresponding hn(4) have the same hardware
address.
- Once the network VF is up, e.g. ifconfig VF up:
o All of the transmission should go through the network VF.
o Most of the reception goes through the network VF.
o Small amount of reception may go through the cooresponding hn(4).
This reception will happen, even if the the cooresponding hn(4) is
down. The cooresponding hn(4) will change the reception interface
to the network VF, so that network layer and application layer will
be tricked into thinking that these packets were received by the
network VF.
o The cooresponding hn(4) pretends the physical link is down.
- Once the network VF is down or detached:
o All of the transmission should go through the cooresponding hn(4).
o All of the reception goes through the cooresponding hn(4).
o The cooresponding hn(4) fallbacks to the original physical link
detection logic.

All these features are mainly used to help live migration, during which
the network VF will be detached, while the network communication to the
VM must not be cut off. In order to reach this level of live migration
transparency, we use failover mode lagg(4) with the network VF and the
cooresponding hn(4) attached to it.

To ease user configuration for both network VF and non-network VF, the
lagg(4) will be created by the following rules, and the configuration
of the cooresponding hn(4) will be applied to the lagg(4) automatically.

Sponsored by: Microsoft
Differential Revision: https://reviews.freebsd.org/D11635

MFC 317783
hyperv/kvp: Fix pool direcrory and file permission

PR: 209385
Sponsored by: Microsoft

MFC 308664,308742,308743

308664
hyperv/vss: Add driver and tools for VSS

VSS stands for "Volume Shadow Copy Service". Unlike virtual machine
snapshot, it only takes snapshot for the virtual disks, so both
filesystem and applications have to aware of it, and cooperate the
whole VSS process.

This driver exposes two device files to the userland:

/dev/hv_fsvss_dev

Normally userland programs should _not_ mess with this device file.
It is currently used by the hv_vss_daemon(8), which freezes and
thaws the filesystem. NOTE: currently only UFS is supported, if
the system mounts _any_ other filesystems, the hv_vss_daemon(8)
will veto the VSS process.

If hv_vss_daemon(8) was disabled, then this device file must be
opened, and proper ioctls must be issued to keep the VSS working.

/dev/hv_appvss_dev

Userland application can opened this device file to receive the
VSS freeze notification, hold the VSS for a while (mainly to flush
application data to filesystem), release the VSS process, and
receive the VSS thaw notification i.e. applications can run again.

The VSS will still work, even if this device file is not opened.
However, only filesystem consistency is promised, if this device
file is not opened or is not operated properly.

hv_vss_daemon(8) is started by devd(8) by default. It can be disabled
by editting /etc/devd/hyperv.conf.

Submitted by: Hongjiang Zhang <honzhan microsoft com>
Reviewed by: kib, mckusick
Sponsored by: Microsoft
Differential Revision: https://reviews.freebsd.org/D8224

308742
hyperv/vss: Nuke unused variables.

Submitted by: markj
Reported by: markj
Sponsored by: Microsoft

308743
hyperv/vss: Install the userland daemon to /usr/sbin instead of /

Submitted by: markj
Reported by: markj
Sponsored by: Microsoft

MFC 308201

hyperv/kvp: Don't mix message status codes and function return values.

While I'm here, move message status codes to hv_utilreg.h, since they
will be used by the upcoming VSS stuffs.

Submitted by: Hongjiang Zhang <honzhan microsoft com>
Sponsored by: Microsoft
Differential Revision: https://reviews.freebsd.org/D8391

MFC 293653

hyperv/kvp_daemon: Make poll(2) block indefinitely

Submitted by: Jun Su <junsu microsoft com>
Reviewed by: Dexuan Cui <decui microsoft com>, me, adrain
Approved by: adrian
Sponsored by: Microsoft OSTC
Differential Revision: https://reviews.freebsd.org/D4762

MFC r274370:

Rename variable name from 'index' to 'idx' to avoid shadowing index(3).

Noticed by: dim

MFC r274383:

Test errno against EEXIST as well.

MFV r273747:

Remove an extra copy of hv_kvp_daemon(8) [1].

While I'm there also correct typos in OptionalObsoleteFiles and add
information of the command line options for hv_kvp_daemon(8).

Reported by: jmg [1]
Reviewed by: jmg

MFC r271493,271688-271689,271696,271854,272139-272143:

Import HyperV Key-Value Pair (KVP) driver and daemon code by Microsoft,
many thanks for their continued support of FreeBSD.

While I'm there, also implement a new build knob, WITHOUT_HYPERV to
disable building and installing of the HyperV utilities when necessary.

The HyperV utilities are only built for i386 and amd64 targets.

Approved by: re (gjb)

Import HyperV Key-Value Pair (KVP) driver and daemon code by Microsoft,
many thanks for their continued support of FreeBSD.

While I'm there, also implement a new build knob, WITHOUT_HYPERV to
disable building and installing of the HyperV utilities when necessary.

The HyperV utilities are only built for i386 and amd64 targets.

This is a stable/10 candidate for inclusion with 10.1-RELEASE.

Submitted by: Wei Hu <weh microsoft com>
MFC after: 1 week