xen: add and enable Xen console for PVH guests

This adds and enables the PV console used on XEN kernels to
GENERIC/XENHVM kernels in order for it to be used on PVH.

Approved by: gibbs
Sponsored by: Citrix Systems R&D

dev/xen/console/console.c:
 - Define console_page.
 - Move xc_printf debug function from i386 XEN code to generic console
   code.
 - Rework xc_printf.
 - Use xen_initial_domain instead of open-coded checks for Dom0.
 - Gate the attach of the PV console to PV(H) guests.

dev/xen/console/xencons_ring.c:
 - Allow the PV Xen console to output earlier by directly signaling
   the event channel in start_info if the event channel is not yet
   initialized.
 - Use HYPERVISOR_start_info instead of xen_start_info.

i386/include/xen/xen-os.h:
 - Remove prototype for xc_printf since it's now declared in global
   xen-os.h

i386/xen/xen_machdep.c:
 - Remove previous version of xc_printf.
 - Remove definition of console_page (now it's defined in the console
   itself).
 - Fix some printf formatting errors.

x86/xen/pv.c:
 - Add some early boot debug messages using xc_printf.
 - Set console_page based on the value passed in start_info.

xen/xen-os.h:
 - Declare console_page and add prototype for xc_printf.

1 files changed, 4 insertions, 0 deletions

diff --git a/sys/xen/xen-os.h b/sys/xen/xen-os.h
index 62b5bf6..7dd9c7e 100644
--- a/sys/xen/xen-os.h
+++ b/sys/xen/xen-os.h
@@ -55,6 +55,7 @@ extern start_info_t *HYPERVISOR_start_info;
 
 /* XXX: we need to get rid of this and use HYPERVISOR_start_info directly */
 extern struct xenstore_domain_interface *xen_store;
+extern char *console_page;
 
 enum xen_domain_type {
 	XEN_NATIVE,             /* running on bare hardware    */
@@ -89,6 +90,9 @@ xen_initial_domain(void)
 	    (HYPERVISOR_start_info->flags & SIF_INITDOMAIN) != 0);
 }
 
+/* Debug/emergency function, prints directly to hypervisor console */
+void xc_printf(const char *, ...) __printflike(1, 2);
+
 #ifndef xen_mb
 #define xen_mb() mb()
 #endif