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

1 files changed, 9 insertions, 138 deletions

diff --git a/sys/amd64/conf/XENHVM b/sys/amd64/conf/XENHVM
index 51f1256..d9482e5 100644
--- a/sys/amd64/conf/XENHVM
+++ b/sys/amd64/conf/XENHVM
@@ -1,152 +1,23 @@
 #
 # XENHVM -- Xen HVM kernel configuration file for FreeBSD/amd64
 #
-# For more information on this file, please read the config(5) manual page,
-# and/or the handbook section on Kernel Configuration Files:
-#
-#    http://www.FreeBSD.org/doc/en_US.ISO8859-1/books/handbook/kernelconfig-config.html
-#
-# The handbook is also available locally in /usr/share/doc/handbook
-# if you've installed the doc distribution, otherwise always see the
-# FreeBSD World Wide Web server (http://www.FreeBSD.org/) for the
-# latest information.
-#
-# An exhaustive list of options and more detailed explanations of the
-# device lines is also present in the ../../conf/NOTES and NOTES files.
-# If you are in doubt as to the purpose or necessity of a line, check first
-# in NOTES.
-#
 # $FreeBSD$
-
-cpu		HAMMER
+#
+include		GENERIC
 ident		XENHVM
 
-makeoptions	DEBUG=-g		# Build kernel with gdb(1) debug symbols
 makeoptions	MODULES_OVERRIDE=""
 
-options 	SCHED_ULE		# ULE scheduler
-options 	PREEMPTION		# Enable kernel thread preemption
-options 	INET			# InterNETworking
-options 	INET6			# IPv6 communications protocols
-options 	SCTP			# Stream Control Transmission Protocol
-options 	FFS			# Berkeley Fast Filesystem
-options 	SOFTUPDATES		# Enable FFS soft updates support
-options 	UFS_ACL			# Support for access control lists
-options 	UFS_DIRHASH		# Improve performance on big directories
-options 	UFS_GJOURNAL		# Enable gjournal-based UFS journaling
-options 	MD_ROOT			# MD is a potential root device
-options 	NFSCLIENT		# Network Filesystem Client
-options 	NFSSERVER		# Network Filesystem Server
-options 	NFSLOCKD		# Network Lock Manager
-options 	NFS_ROOT		# NFS usable as /, requires NFSCLIENT
-options 	MSDOSFS			# MSDOS Filesystem
-options 	CD9660			# ISO 9660 Filesystem
-options 	PROCFS			# Process filesystem (requires PSEUDOFS)
-options 	PSEUDOFS		# Pseudo-filesystem framework
-options 	GEOM_PART_GPT		# GUID Partition Tables.
-options 	GEOM_LABEL		# Provides labelization
-options 	COMPAT_FREEBSD32	# Compatible with i386 binaries
-options 	COMPAT_FREEBSD4		# Compatible with FreeBSD4
-options 	COMPAT_FREEBSD5		# Compatible with FreeBSD5
-options 	COMPAT_FREEBSD6		# Compatible with FreeBSD6
-options 	COMPAT_FREEBSD7		# Compatible with FreeBSD7
-options 	SCSI_DELAY=5000		# Delay (in ms) before probing SCSI
-options 	KTRACE			# ktrace(1) support
-options 	STACK			# stack(9) support
-options 	SYSVSHM			# SYSV-style shared memory
-options 	SYSVMSG			# SYSV-style message queues
-options 	SYSVSEM			# SYSV-style semaphores
-options 	_KPOSIX_PRIORITY_SCHEDULING # POSIX P1003_1B real-time extensions
-options 	KBD_INSTALL_CDEV	# install a CDEV entry in /dev
-options 	HWPMC_HOOKS		# Necessary kernel hooks for hwpmc(4)
-options 	AUDIT			# Security event auditing
-#options 	KDTRACE_FRAME		# Ensure frames are compiled in
-#options 	KDTRACE_HOOKS		# Kernel DTrace hooks
+#
+# Adaptive locks rely on a lock-free pointer read to determine the run state
+# of the thread holding a lock when under contention; under a virtualisation
+# system, the thread run state may not accurately reflect whether the thread
+# (or rather its host VCPU) is actually executing.  As such, disable this
+# optimisation.
+#
 options 	NO_ADAPTIVE_MUTEXES
 options 	NO_ADAPTIVE_RWLOCKS
 
-# Debugging for use in -current
-options 	KDB			# Enable kernel debugger support.
-options 	DDB			# Support DDB.
-options 	GDB			# Support remote GDB.
-options 	DEADLKRES		# Enable the deadlock resolver
-options 	INVARIANTS		# Enable calls of extra sanity checking
-options 	INVARIANT_SUPPORT	# Extra sanity checks of internal structures, required by INVARIANTS
-options 	WITNESS			# Enable checks to detect deadlocks and cycles
-options 	WITNESS_SKIPSPIN	# Don't run witness on spinlocks for speed
-
-# Make an SMP-capable kernel by default
-options 	SMP			# Symmetric MultiProcessor Kernel
-
-# CPU frequency control
-device		cpufreq
-
-# Bus support.
-device		acpi
-device		pci
-
-# Floppy drives
-device		fdc
-
 # Xen HVM support
 options 	XENHVM
 device		xenpci
-
-# ATA and ATAPI devices
-device		ata
-device		atadisk		# ATA disk drives
-device		ataraid		# ATA RAID drives
-device		atapicd		# ATAPI CDROM drives
-device		atapifd		# ATAPI floppy drives
-device		atapist		# ATAPI tape drives
-options 	ATA_STATIC_ID	# Static device numbering
-
-# SCSI peripherals
-device		scbus		# SCSI bus (required for SCSI)
-device		ch		# SCSI media changers
-device		da		# Direct Access (disks)
-device		sa		# Sequential Access (tape etc)
-device		cd		# CD
-device		pass		# Passthrough device (direct SCSI access)
-device		ses		# SCSI Environmental Services (and SAF-TE)
-
-
-# atkbdc0 controls both the keyboard and the PS/2 mouse
-device		atkbdc		# AT keyboard controller
-device		atkbd		# AT keyboard
-device		psm		# PS/2 mouse
-
-device		kbdmux		# keyboard multiplexer
-
-device		vga		# VGA video card driver
-
-device		splash		# Splash screen and screen saver support
-
-# syscons is the default console driver, resembling an SCO console
-device		sc
-
-device		agp		# support several AGP chipsets
-
-# Serial (COM) ports
-device		uart		# Generic UART driver
-
-# PCI Ethernet NICs that use the common MII bus controller code.
-# NOTE: Be sure to keep the 'device miibus' line in order to use these NICs!
-device		miibus		# MII bus support
-device		re		# RealTek 8139C+/8169/8169S/8110S
-
-# Pseudo devices.
-device		loop		# Network loopback
-device		random		# Entropy device
-device		ether		# Ethernet support
-device		tun		# Packet tunnel.
-device		pty		# BSD-style compatibility pseudo ttys
-device		md		# Memory "disks"
-device		gif		# IPv6 and IPv4 tunneling
-device		faith		# IPv6-to-IPv4 relaying (translation)
-device		firmware	# firmware assist module
-
-# The `bpf' device enables the Berkeley Packet Filter.
-# Be aware of the administrative consequences of enabling this!
-# Note that 'bpf' is required for DHCP.
-device		bpf		# Berkeley packet filter