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

Update Xen headers from 4.2 to 4.6

Pull the latest headers for Xen which allow us to add support for ARM and
use new features in FreeBSD.

This is a verbatim copy of the xen/include/public so every headers which
don't exits anymore in the Xen repositories have been dropped.

Note the interface version hasn't been bumped, it will be done in a
follow-up. Although, it requires fix in the code to get it compiled:

- sys/xen/xen_intr.h: evtchn_port_t is already defined in the headers so
drop it.

- {amd64,i386}/include/intr_machdep.h: NR_EVENT_CHANNELS now depends on
xen/interface/event_channel.h, so include it.

- {amd64,i386}/{amd64,i386}/support.S: It's not neccessary to include
machine/intr_machdep.h. This is also fixing build compilation with the
new headers.

- dev/xen/blkfront/blkfront.c: The typedef for blkif_request_segmenthas
been dropped. So directly use struct blkif_request_segment

Finally, modify xen/interface/xen-compat.h to throw a preprocessing error if
__XEN_INTERFACE_VERSION__ is not set. This is allow us to catch any file
where xen/xen-os.h is not correctly included.

Submitted by: Julien Grall <julien.grall@citrix.com>
Reviewed by: royger
Differential Revision: https://reviews.freebsd.org/D3805
Sponsored by: Citrix Systems R&D

msi: add Xen MSI implementation

This patch adds support for MSI interrupts when running on Xen. Apart
from adding the Xen related code needed in order to register MSI
interrupts this patch also makes the msi_init function a hook in
init_ops, so different MSI implementations can have different
initialization functions.

Sponsored by: Citrix Systems R&D

xen/interface/physdev.h:
- Add the MAP_PIRQ_TYPE_MULTI_MSI to map multi-vector MSI to the Xen
public interface.

x86/include/init.h:
- Add a hook for setting custom msi_init methods.

amd64/amd64/machdep.c:
i386/i386/machdep.c:
- Set the default msi_init hook to point to the native MSI
initialization method.

x86/xen/pv.c:
- Set the Xen MSI init hook when running as a Xen guest.

x86/x86/local_apic.c:
- Call the msi_init hook instead of directly calling msi_init.

xen/xen_intr.h:
x86/xen/xen_intr.c:
- Introduce support for registering/releasing MSI interrupts with
Xen.
- The MSI interrupts will use the same PIC as the IO APIC interrupts.

xen/xen_msi.h:
x86/xen/xen_msi.c:
- Introduce a Xen MSI implementation.

x86/xen/xen_nexus.c:
- Overwrite the default MSI hooks in the Xen Nexus to use the Xen MSI
implementation.

x86/xen/xen_pci.c:
- Introduce a Xen specific PCI bus that inherits from the ACPI PCI
bus and overwrites the native MSI methods.
- This is needed because when running under Xen the MSI messages used
to configure MSI interrupts on PCI devices are written by Xen
itself.

dev/acpica/acpi_pci.c:
- Lower the quality of the ACPI PCI bus so the newly introduced Xen
PCI bus can take over when needed.

conf/files.i386:
conf/files.amd64:
- Add the newly created files to the build process.

Upgrade Xen interface headers to Xen 4.2.1.

Move FreeBSD from interface version 0x00030204 to 0x00030208.
Updates are required to our grant table implementation before we
can bump this further.

sys/xen/hvm.h:
Replace the implementation of hvm_get_parameter(), formerly located
in sys/xen/interface/hvm/params.h. Linux has a similar file which
primarily stores this function.

sys/xen/xenstore/xenstore.c:
Include new xen/hvm.h header file to get hvm_get_parameter().

sys/amd64/include/xen/xen-os.h:
sys/i386/include/xen/xen-os.h:
Correctly protect function definition and variables from being
included into assembly files in xen-os.h

Xen memory barriers are now prefixed with "xen_" to avoid conflicts
with OS native primatives. Define Xen memory barriers in terms of
the native FreeBSD primatives.

Sponsored by: Spectra Logic Corporation
Reviewed by: Roger Pau Monné
Tested by: Roger Pau Monné
Obtained from: Roger Pau Monné (bug fixes)

partial update to interface headers to 3.2

MFC after: 1 month

Import OS interfaces to Xen services.

MFC after: 2 weeks