Only define the full inm_print() if KTR_IGMPV3 is enabled at compile time.
xen: defer xenstore initialization until xenstored is started

The xenstore related devices in the kernel cannot be started until
xenstored is running, which will happen later in the Dom0 case. If
start_info_t doesn't contain a valid xenstore event channel, defer all
xenstore related devices attachment to later.

Sponsored by: Citrix Systems R&D

dev/xen/xenstore/xenstore.c:
 - Prevent xenstore from trying to attach it's descendant devices if
   xenstore is not initialized.
 - Add a callback in the xenstore interrupt filter that will trigger
   the plug of xenstore descendant devices on the first received
   interrupt. This interrupt is generated when xenstored attaches to
   the event channel, and serves as a notification that xenstored is
   running.
xen: convert the xenstore user-space char device to a newbus device

Convert the xenstore user-space device (/dev/xen/xenstore) to a device
using the newbus interface. This allows us to make the device
initialization dependant on the initialization of xenstore itself in
the kernel.

Sponsored by: Citrix Systems R&D

dev/xen/xenstore/xenstore.c:
 - Convert to a newbus device, this removes the xs_dev_init function.

xen/xenstore/xenstore_internal.h:
 - Remove xs_dev_init prototype.

dev/xen/xenstore/xenstore.c:
 - Don't call xs_dev_init anymore, the device will attach itself when
   xenstore is started.
xen: add xenstored user-space device

This device is used by the user-space daemon that runs xenstore
(xenstored). It allows xenstored to map the xenstore memory page, and
reports the event channel xenstore is using.

Sponsored by: Citrix Systems R&D

dev/xen/xenstore/xenstored_dev.c:
 - Add the xenstored character device that's used to map the xenstore
   memory into user-space, and to report the event channel used by
   xenstore.

conf/files:
 - Add the device to the build process.
xen/balloon: fix accounting of current memory pages on PVH

Using realmem on PVH is not realiable, since in this case the realmem value
is computed from Maxmem, which contains the higher memory address found. Use
HYPERVISOR_start_info->nr_pages instead, which is set by the hypervisor and
contains the exact number of memory pages assigned to the domain.

Sponsored by: Citrix Systems R&D
xen: fix blkback pushing responses before releasing internal resources

Fix a problem where the blockback driver could run out of requests,
despite the fact that we allocate enough request and reqlist
structures to satisfy the maximum possible number of requests.

The problem was that we were sending responses back to the other
end (blockfront) before freeing resources. The Citrix Windows
driver is pretty agressive about queueing, and would queue more I/O
to us immediately after we sent responses to it. We would run into
a resource shortage and stall out I/O until we freed resources.

It isn't clear whether the request shortage condition was an
indirect cause of the I/O hangs we've been seeing between Windows
with the Citrix PV drivers and FreeBSD's blockback, but the above
problem is certainly a bug.

Sponsored by: Spectra Logic
Submitted by: ken
Reviewed by: royger

dev/xen/blkback/blkback.c:
 - Break xbb_send_response() into two sub-functions,
   xbb_queue_response() and xbb_push_responses().
   Remove xbb_send_response(), because it is no longer
   used.

 - Adjust xbb_complete_reqlist() so that it calls the
   two new functions, and holds the mutex around both
   calls.  The mutex insures that another context
   can't come along and push responses before we've
   freed our resources.

 - Change xbb_release_reqlist() so that it requires
   the mutex to be held instead of acquiring the mutex
   itself.  Both callers could easily hold the mutex
   while calling it, and one really needs to hold the
   mutex during the call.

 - Add two new counters, accessible via sysctl
   variables.  The first one counts the number of
   I/Os that are queued and waiting to be pushed
   (reqs_queued_for_completion).  The second one
   (reqs_completed_with_error) counts the number of
   requests we've completed with an error status.