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@redhat.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 1b4b5fa498b3a611642b1bd1e766c16272692ec1..6cfb708408e950412f6c9c3ebbb82e0d3f60bcc9 100644 (file)
--- 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 619a6f8d65a22c20b36395fe4d4d1ba2d89c7729..4e10876e62fc98d3bb68f5abd65a0fb467dc70a2 100644 (file)
--- 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 a4f27fbdf5494ee885caa967a24d1934744386a3..248e6e3b9b734d515e0c74f95aabd1de2dd57b6d 100644 (file)
--- 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 8fb01c32aa3bb7eaf44f5b9e63e316628dd935c1..028ed75d4864a6812deca019f592774eb991711a 100644 (file)
--- 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);