Add support for suspend/resume/migration operations when running as a
Xen PVHVM guest.

Submitted by:	Roger Pau Monné
Sponsored by:	Citrix Systems R&D
Reviewed by:	gibbs
Approved by:	re (blanket Xen)
MFC after:	2 weeks

sys/amd64/amd64/mp_machdep.c:
sys/i386/i386/mp_machdep.c:
	- Make sure that are no MMU related IPIs pending on migration.
	- Reset pending IPI_BITMAP on resume.
	- Init vcpu_info on resume.

sys/amd64/include/intr_machdep.h:
sys/i386/include/intr_machdep.h:
sys/x86/acpica/acpi_wakeup.c:
sys/x86/x86/intr_machdep.c:
sys/x86/isa/atpic.c:
sys/x86/x86/io_apic.c:
sys/x86/x86/local_apic.c:
	- Add a "suspend_cancelled" parameter to pic_resume().  For the
	  Xen PIC, restoration of interrupt services differs between
	  the aborted suspend and normal resume cases, so we must provide
	  this information.

sys/dev/acpica/acpi_timer.c:
sys/dev/xen/timer/timer.c:
sys/timetc.h:
	- Don't swap out "suspend safe" timers across a suspend/resume
	  cycle.  This includes the Xen PV and ACPI timers.

sys/dev/xen/control/control.c:
	- Perform proper suspend/resume process for PVHVM:
		- Suspend all APs before going into suspension, this allows us
		  to reset the vcpu_info on resume for each AP.
		- Reset shared info page and callback on resume.

sys/dev/xen/timer/timer.c:
	- Implement suspend/resume support for the PV timer. Since FreeBSD
	  doesn't perform a per-cpu resume of the timer, we need to call
	  smp_rendezvous in order to correctly resume the timer on each CPU.

sys/dev/xen/xenpci/xenpci.c:
	- Don't reset the PCI interrupt on each suspend/resume.

sys/kern/subr_smp.c:
	- When suspending a PVHVM domain make sure there are no MMU IPIs
	  in-flight, or we will get a lockup on resume due to the fact that
	  pending event channels are not carried over on migration.
	- Implement a generic version of restart_cpus that can be used by
	  suspended and stopped cpus.

sys/x86/xen/hvm.c:
	- Implement resume support for the hypercall page and shared info.
	- Clear vcpu_info so it can be reset by APs when resuming from
	  suspension.

sys/dev/xen/xenpci/xenpci.c:
sys/x86/xen/hvm.c:
sys/x86/xen/xen_intr.c:
	- Support UP kernel configurations.

sys/x86/xen/xen_intr.c:
	- Properly rebind per-cpus VIRQs and IPIs on resume.