[Pkg-xen-devel] xen 2.6.26 on amd64 console troubles

[Ian Campbell]

On Fri, 2008-10-17 at 10:12 +0200, Bastian Blank wrote:
> On Fri, Oct 17, 2008 at 07:27:05AM +0100, Ian Campbell wrote:
> > It did work, I just needed to update my initrd (I thought I'd get away
> > with the 2.6.26-1-xen-amd64 since localversion was the same but didn't
> > for some reason).
> 
> It should also use a add_preferred_console("hvc", 0, NULL); in the not
> dom0 case like the new code. This way it will get the console always.

I'll give it a go. Wasn't there some more complex patches upstream to do
with handing over to pvfb when it came online? *scrobbles around in git*
this:

http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=9e124fe16ff24746d6de5a2ad685266d7bce0e08;hp=a15af1c9ea2750a9ff01e51615c45950bad8221b

commit 9e124fe16ff24746d6de5a2ad685266d7bce0e08
Author: Markus Armbruster <armbru at redhat.com>
Date:   Mon May 26 23:31:07 2008 +0100

    xen: Enable console tty by default in domU if it's not a dummy
    
    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 at redhat.com>
    Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge at citrix.com>
    Signed-off-by: Thomas Gleixner <tglx at linutronix.de>

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 1b4b5fa..6cfb708 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1256,8 +1256,10 @@ 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 b/drivers/video/xen-fbfront.c
index 619a6f8..4e10876 100644
--- a/drivers/video/xen-fbfront.c
+++ b/drivers/video/xen-fbfront.c
@@ -18,6 +18,7 @@
  * frame buffer.
  */
 
+#include <linux/console.h>
 #include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/fb.h>
@@ -48,6 +49,7 @@ struct xenfb_info {
 
 static u32 xenfb_mem_len = XENFB_WIDTH * XENFB_HEIGHT * XENFB_DEPTH / 8;
 
+static void xenfb_make_preferred_console(void);
 static int xenfb_remove(struct xenbus_device *);
 static void xenfb_init_shared_page(struct xenfb_info *);
 static int xenfb_connect_backend(struct xenbus_device *, struct xenfb_info *);
@@ -348,6 +350,7 @@ static int __devinit xenfb_probe(struct xenbus_device *dev,
 	if (ret < 0)
 		goto error;
 
+	xenfb_make_preferred_console();
 	return 0;
 
  error_nomem:
@@ -358,6 +361,28 @@ static int __devinit xenfb_probe(struct xenbus_device *dev,
 	return ret;
 }
 
+static __devinit void
+xenfb_make_preferred_console(void)
+{
+	struct console *c;
+
+	if (console_set_on_cmdline)
+		return;
+
+	acquire_console_sem();
+	for (c = console_drivers; c; c = c->next) {
+		if (!strcmp(c->name, "tty") && c->index == 0)
+			break;
+	}
+	release_console_sem();
+	if (c) {
+		unregister_console(c);
+		c->flags |= CON_CONSDEV;
+		c->flags &= ~CON_PRINTBUFFER; /* don't print again */
+		register_console(c);
+	}
+}
+
 static int xenfb_resume(struct xenbus_device *dev)
 {
 	struct xenfb_info *info = dev->dev.driver_data;
diff --git a/include/linux/console.h b/include/linux/console.h
index a4f27fb..248e6e3 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -108,6 +108,8 @@ struct console {
 	struct	 console *next;
 };
 
+extern int console_set_on_cmdline;
+
 extern int add_preferred_console(char *name, int idx, char *options);
 extern int update_console_cmdline(char *name, int idx, char *name_new, int idx_new, char *options);
 extern void register_console(struct console *);
diff --git a/kernel/printk.c b/kernel/printk.c
index 8fb01c3..028ed75 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -121,6 +121,8 @@ struct console_cmdline
 static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];
 static int selected_console = -1;
 static int preferred_console = -1;
+int console_set_on_cmdline;
+EXPORT_SYMBOL(console_set_on_cmdline);
 
 /* Flag: console code may call schedule() */
 static int console_may_schedule;
@@ -890,6 +892,7 @@ static int __init console_setup(char *str)
 	*s = 0;
 
 	__add_preferred_console(buf, idx, options, brl_options);
+	console_set_on_cmdline = 1;
 	return 1;
 }
 __setup("console=", console_setup);


Ian.
-- 
Ian Campbell
Current Noise: Pelican - Red Ran Amber

In the eyes of my dog, I'm a man.
		-- Martin Mull