From: Aron Griffis <agriffis@redhat.com>
Subject: [RHEL5.1 PATCH][XEN] use xencons=xvc by default on non-x86
Date: Wed, 8 Aug 2007 21:17:29 -0400
Bugzilla: 249100
Message-Id: <20070809011728.GB27167@redhat.com>
Changelog: [XEN] use xencons=xvc by default on non-x86


bz249100
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=249100

Summary
-------
This patch changes the default xencons setting to "xvc" for non-x86
and non-x86_64 systems, in particular ia64.  The goal is to get
a login prompt on dom0 without needing to specify xencons=xvc
console=xvc0 on the kernel command-line.

Explanation
-----------
ia64 sets the current console in EFI, i.e. serial or VGA.  This
console setting is honored by bare-metal Linux, and corresponding
support is in the Xen hypervisor.  This means that ia64 users are
accustomed to not setting any console variables on the kernel
command-line, and everything works as expected.

This is different from x86, of course, where console=ttyS0 or
a similar setting is required for any headless setup.  Similarly on
RHEL5 Xen, xencons=xvc console=xvc0 is recommended.

There are two possible routes to making this work on ia64:

1. Since the default presently is xencons=ttyS, hack kudzu to check
   /dev/ttyS* in addition to /dev/xvc0.  I tried this approach first
   (see the bugzilla) but met resistance to further propogating the
   xencons=ttyS badness.

    OR

2. Follow upstream's lead by making xencons=xvc the default.  See
   http://xenbits.xensource.com/linux-2.6.18-xen.hg?rev/12c399692d44

This patch implements #2.  It avoids changing the default xencons=ttyS
for x86 and x86_64 since those were supported in GA, but it uses the
new default for other platforms.  At this point that would only be
ia64.

I've tested this patch on rx3600 successfully.

Thanks,
Aron

diff -ur linux-2.6.18.ia64.old/drivers/xen/console/console.c linux-2.6.18.ia64/drivers/xen/console/console.c
--- linux-2.6.18.ia64.old/drivers/xen/console/console.c	2007-08-08 15:55:35.000000000 -0400
+++ linux-2.6.18.ia64/drivers/xen/console/console.c	2007-08-08 16:14:34.000000000 -0400
@@ -194,7 +194,11 @@
 
 	if (is_initial_xendomain()) {
 		if (xc_mode == XC_DEFAULT)
+#if defined(__i386__) || defined(__x86_64__)
 			xc_mode = XC_SERIAL;
+#else
+			xc_mode = XC_XVC;
+#endif
 		kcons_info.write = kcons_write_dom0;
 	} else {
 		if (!xen_start_info->console.domU.evtchn)