xen: use the hvc console infrastructure for Xen console

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: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Acked-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Olof Johansson <olof@lixom.net>

2 files changed, 7 insertions, 1 deletions

diff --git a/arch/i386/xen/events.c b/arch/i386/xen/events.c
index 4103b8bf22fd..8904acc20f8c 100644
--- a/arch/i386/xen/events.c
+++ b/arch/i386/xen/events.c
@@ -244,7 +244,7 @@ static int find_unbound_irq(void)
         return irq;
 }
 
-static int bind_evtchn_to_irq(unsigned int evtchn)
+int bind_evtchn_to_irq(unsigned int evtchn)
 {
         int irq;
 
@@ -269,6 +269,7 @@ static int bind_evtchn_to_irq(unsigned int evtchn)
 
         return irq;
 }
+EXPORT_SYMBOL_GPL(bind_evtchn_to_irq);
 
 static int bind_ipi_to_irq(unsigned int ipi, unsigned int cpu)
 {
diff --git a/arch/x86_64/kernel/early_printk.c b/arch/x86_64/kernel/early_printk.c
index 296d2b0c5d88..fd9aff3f3890 100644
--- a/arch/x86_64/kernel/early_printk.c
+++ b/arch/x86_64/kernel/early_printk.c
@@ -6,6 +6,7 @@
 #include <asm/io.h>
 #include <asm/processor.h>
 #include <asm/fcntl.h>
+#include <xen/hvc-console.h>
 
 /* Simple VGA output */
 
@@ -242,6 +243,10 @@ static int __init setup_early_printk(char *buf)
                 simnow_init(buf + 6);
                 early_console = &simnow_console;
                 keep_early = 1;
+#ifdef CONFIG_HVC_XEN
+        } else if (!strncmp(buf, "xen", 3)) {
+                early_console = &xenboot_console;
+#endif
         }
 
         if (keep_early)