Amit,
can you have a look at the patch below and give feedback or apply
if appropriate?
---
On s390 I have seen some random "Warning: unable to open an initial
console" boot failure. Turns out that tty_open fails, because the
hvc_alloc was not yet done. In former times this could not happen,
since the probe function automatically called hvc_alloc. With newer
versions (multiport) some host<->guest interaction is required
before hvc_alloc is called. This might be too late, especially if
an initramfs is involved. Lets use a completion if we have
multiport and an early console.
Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
---
drivers/char/virtio_console.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
Index: b/drivers/char/virtio_console.c
===================================================================
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -19,6 +19,7 @@
*/
#include <linux/cdev.h>
#include <linux/debugfs.h>
+#include <linux/completion.h>
#include <linux/device.h>
#include <linux/err.h>
#include <linux/fs.h>
@@ -73,6 +74,7 @@ struct ports_driver_data {
static struct ports_driver_data pdrvdata;
DEFINE_SPINLOCK(pdrvdata_lock);
+DECLARE_COMPLETION(port_added);
/* This struct holds information that's relevant only for console ports */
struct console {
@@ -1352,6 +1354,7 @@ static void handle_control_message(struc
break;
init_port_console(port);
+ complete(&port_added);
/*
* Could remove the port here in case init fails - but
* have to notify the host first.
@@ -1648,6 +1651,10 @@ static int __devinit virtcons_probe(stru
struct ports_device *portdev;
int err;
bool multiport;
+ bool early = early_put_chars != 0;
+
+ /* Ensure to read early_put_chars now */
+ barrier();
portdev = kmalloc(sizeof(*portdev), GFP_KERNEL);
if (!portdev) {
@@ -1719,6 +1726,17 @@ static int __devinit virtcons_probe(stru
__send_control_msg(portdev, VIRTIO_CONSOLE_BAD_ID,
VIRTIO_CONSOLE_DEVICE_READY, 1);
+
+ /* If there was an early virtio console, assume that there are no
+ * other consoles. We need to wait until the hvc_alloc matches the
+ * hvc_instantiate, otherwise tty_open will complain, resulting in
+ * a "Warning: unable to open an initial console" boot failure.
+ * Without multiport this is done in add_port above. With multiport
+ * this might take some host<->guest communication - thus we have to
+ * wait. */
+ if (multiport && early)
+ wait_for_completion(&port_added);
+
return 0;
free_vqs:
--
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