-tip testing found the following build breakage:

  drivers/built-in.o: In function `xen_suspend':
  manage.c:(.text+0x4390f): undefined reference to `xen_console_resume'

with this config:

  http://redhat.com/~mingo/misc/config-Thu_May_29_09_23_16_CEST_2008.bad

i have bisected it down to:

|  commit 0e91398f
|  Author: Jeremy Fitzhardinge <jeremy@goop.org>
|  Date:   Mon May 26 23:31:27 2008 +0100
|
|      xen: implement save/restore

the problem is that drivers/xen/manage.c is built unconditionally if
CONFIG_XEN is enabled and makes use of xen_suspend(), but
drivers/char/hvc_xen.c, where the xen_suspend() method is implemented,
is only build if CONFIG_HVC_XEN=y as well.

i have solved this by providing a NOP implementation for xen_suspend()
in the !CONFIG_HVC_XEN case.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Add code to:

 1. Deal with the console page being canonicalized.  During save, the
    console's mfn in the start_info structure is canonicalized to a pfn.
    In order to deal with that, we always use a copy of the pfn and
    indirect off that all the time.  However, we fall back to using the
    mfn if the pfn hasn't been initialized yet.

 2. Restore the console event channel, and rebind it to the existing irq.
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Add a couple of functions which can write directly to the Xen console
for debugging.  This output ends up on the host's dom0 console
(assuming it allows the domain to write there).
Signed-off-by: NJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>

Implement a Xen back-end for hvc console.

* * *
Add early printk support via hvc console, enable using
"earlyprintk=xen" on the kernel command line.

From: Gerd Hoffmann <kraxel@suse.de>
Signed-off-by: NJeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: NChris Wright <chrisw@sous-sol.org>
Acked-by: NIngo Molnar <mingo@elte.hu>
Acked-by: NOlof Johansson <olof@lixom.net>