Without console= arguments on the kernel command line, the first

console to register becomes enabled and the preferred console (the one

behind /dev/console).  This is normally tty (assuming

CONFIG_VT_CONSOLE is enabled, which it commonly is).
This is okay as long tty is a useful console.  But unless we have the

PV framebuffer, and it is enabled for this domain, tty0 in domU is

merely a dummy.  In that case, we want the preferred console to be the

Xen console hvc0, and we want it without having to fiddle with the

kernel command line.  Commit b8c2d3dfbc117dff26058fbac316b8acfc2cb5f7

did that for us.
Since we now have the PV framebuffer, we want to enable and prefer tty

again, but only when PVFB is enabled.  But even then we still want to

enable the Xen console as well.
Problem: when tty registers, we can't yet know whether the PVFB is

enabled.  By the time we can know (xenstore is up), the console setup

game is over.
Solution: enable console tty by default, but keep hvc as the preferred

console.  Change the preferred console to tty when PVFB probes

successfully, unless we've been given console kernel parameters.
Signed-off-by: Markus Armbruster <armbru@redhat.com>

---

 arch/x86/xen/enlighten.c    |    4 +++-

 drivers/video/xen-fbfront.c |   25 +++++++++++++++++++++++++

 include/linux/console.h     |    2 ++

 kernel/printk.c             |    3 +++

 4 files changed, 33 insertions(+), 1 deletions(-)
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c

index c8a56e4..a9f8d6a 100644

--- a/arch/x86/xen/enlighten.c

+++ b/arch/x86/xen/enlighten.c

@@ -1242,8 +1242,10 @@ asmlinkage void __init xen_start_kernel(void)

 		? __pa(xen_start_info->mod_start) : 0;

 	boot_params.hdr.ramdisk_size = xen_start_info->mod_len;
-	if (!is_initial_xendomain())

+	if (!is_initial_xendomain()) {

+		add_preferred_console("tty", 0, NULL);

 		add_preferred_console("hvc", 0, NULL);

+	}
 	/* Start the world */

 	start_kernel();

diff --git a/drivers/video/xen-fbfront.c...
[ message continues ]

On Wed, 21 May 2008 10:38:50 +0200
What a stunningly good changelog - I'd buy the tee-shirt.
Ack on the non-xen bits.

--