MFC r341484

Always treat firmware request and response sizes as unsigned.

This fixes an incomplete bounds check on the guest-supplied request
size where a very large request size could be interpreted as a negative
value and not be caught by the bounds check.

Submitted by: jhb
Reported by: Reno Robert
Approved by: so
Security: FreeBSD-SA-18:14.bhyve
Security: CVE-2018-17160

MFC r336188:

Improve bhyve exit(3) error code.

The bhyve(8) exit status indicates how the VM was terminated:

0 rebooted
1 powered off
2 halted
3 triple fault

The problem is when we have wrappers around bhyve that parses the exit
error code and gets an exit(1) for an error but interprets it as "powered off".
So to mitigate this issue and makes it less error prone for third part
applications, I have added a new exit code 4 that is "exited due to an error".

For now the bhyve(8) exit status are:
0 rebooted
1 powered off
2 halted
3 triple fault
4 exited due to an error

Reviewed by: @jhb
Sponsored by: iXsystems Inc.
Differential Revision: https://reviews.freebsd.org/D16161

MFC r335025:

Add SPDX tags to bhyve(8).

Discussed with: rgrimes, pfg and mav.
Obtained from: TrueOS
Sponsored by: iXsystems Inc.

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

Use MIN()/MAX() macros from sys/param.h.

Reviewed by: grehan
Differential Revision: https://reviews.freebsd.org/D6054

Fix post-test typo that snuck in.

Simple sysctl-like firmware query interface. Similar in operation
to the qemu one, and uses the same i/o ports but with different
messaging. Requires the 'bootrom' option to be enabled.

This is used by UEFI (and potentially other BIOSs/firmware) to
request information from bhyve. Currently, only the number of
vCPUs is made available, with more to follow.

A very large thankyou to Ben Perrault who helped out testing
an earlier version of this, and bhyve/Windows in general.

Reviewed by: tychon
Discussed with: neel
Sponsored by: Nahanni Systems