[S390] hvc_iucv: Special handling of IUCV HVC devices

This patch introduces special handling of the IUCV HVC console device.

If the first IUCV HVC terminal is used as (preferred) Linux console, and
needs some special handling for hangup.
The hvc_iucv_private structure contains a flag to indicate whether a IUCV
HVC device is used as a console.

A terminal acting as "console" behaves different if a tty hangup occurs:
If the iucv communication path is severed, a tty hangup is not
triggered (because the HVC layer does not notify its back-end in that case).
Instead, the console session is left unchanged and the IUCV HVC device is
reset to allow re-connects.
Note: Any output between the disconnect and a re-connect is discarded.
Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/char/hvc_iucv.c

@@ -60,6 +60,7 @@ enum tty_state_t {
 struct hvc_iucv_private {
 	struct hvc_struct	*hvc;		/* HVC struct reference */
 	u8			srv_name[8];	/* IUCV service name (ebcdic) */
+	unsigned char		is_console;	/* Linux console usage flag */
 	enum iucv_state_t	iucv_state;	/* IUCV connection status */
 	enum tty_state_t	tty_state;	/* TTY status */
 	struct iucv_path	*path;		/* IUCV path pointer */
@@ -93,6 +94,7 @@ static unsigned long hvc_iucv_devices = 1;
 
 /* Array of allocated hvc iucv tty lines... */
 static struct hvc_iucv_private *hvc_iucv_table[MAX_HVC_IUCV_LINES];
+#define IUCV_HVC_CON_IDX	(0)
 
 /* Kmem cache and mempool for iucv_tty_buffer elements */
 static struct kmem_cache *hvc_iucv_buffer_cache;
@@ -139,7 +141,7 @@ static struct iucv_tty_buffer *alloc_tty_buffer(size_t size, gfp_t flags)
 	bufp = mempool_alloc(hvc_iucv_mempool, flags);
 	if (!bufp)
 		return NULL;
-	memset(bufp, 0, sizeof(struct iucv_tty_buffer));
+	memset(bufp, 0, sizeof(*bufp));
 
 	if (size > 0) {
 		bufp->msg.length = MSG_SIZE(size);
@@ -463,7 +465,7 @@ static int hvc_iucv_put_chars(uint32_t vtermno, const char *buf, int count)
  * @id:	Additional data (originally passed to hvc_alloc): the index of an struct
  *	hvc_iucv_private instance.
  *
- * The function sets the tty state to TTY_OPEN for the struct hvc_iucv_private
+ * The function sets the tty state to TTY_OPENED for the struct hvc_iucv_private
  * instance that is derived from @id. Always returns 0.
  *
  * Locking:	struct hvc_iucv_private->lock, spin_lock_bh
@@ -707,6 +709,9 @@ static void hvc_iucv_path_severed(struct iucv_path *path, u8 ipuser[16])
 
 	/* If the tty has not yet been opened, clean up the hvc_iucv_private
 	 * structure to allow re-connects.
+	 * This is also done for our console device because console hangups
+	 * are handled specially and no notifier is called by HVC.
+	 * The tty session is active (TTY_OPEN) and ready for re-connects...
 	 *
 	 * If it has been opened, let get_chars() return -EPIPE to signal the
 	 * HVC layer to hang up the tty.
@@ -716,7 +721,11 @@ static void hvc_iucv_path_severed(struct iucv_path *path, u8 ipuser[16])
 	if (priv->tty_state == TTY_CLOSED)
 		hvc_iucv_cleanup(priv);
 	else
-		hvc_kick();
+		if (priv->is_console) {
+			hvc_iucv_cleanup(priv);
+			priv->tty_state = TTY_OPENED;
+		} else
+			hvc_kick();
 	spin_unlock(&priv->lock);
 
 	/* finally sever path (outside of priv->lock due to lock ordering) */
@@ -747,7 +756,6 @@ static void hvc_iucv_msg_pending(struct iucv_path *path,
 		return;
 	}
 
-
 	spin_lock(&priv->lock);
 
 	/* reject messages if tty has not yet been opened */
@@ -814,13 +822,14 @@ static struct hv_ops hvc_iucv_ops = {
 
 /**
  * hvc_iucv_alloc() - Allocates a new struct hvc_iucv_private instance
- * @id:	hvc_iucv_table index
+ * @id:			hvc_iucv_table index
+ * @is_console:		Flag if the instance is used as Linux console
  *
  * This function allocates a new hvc_iucv_private structure and stores
  * the instance in hvc_iucv_table at index @id.
  * Returns 0 on success; otherwise non-zero.
  */
-static int __init hvc_iucv_alloc(int id)
+static int __init hvc_iucv_alloc(int id, unsigned int is_console)
 {
 	struct hvc_iucv_private *priv;
 	char name[9];
@@ -842,6 +851,9 @@ static int __init hvc_iucv_alloc(int id)
 		return -ENOMEM;
 	}
 
+	/* set console flag */
+	priv->is_console = is_console;
+
 	/* finally allocate hvc */
 	priv->hvc = hvc_alloc(HVC_IUCV_MAGIC + id, /*		  PAGE_SIZE */
 			      HVC_IUCV_MAGIC + id, &hvc_iucv_ops, 256);
@@ -869,7 +881,8 @@ static int __init hvc_iucv_alloc(int id)
  */
 static int __init hvc_iucv_init(void)
 {
-	int rc, i;
+	int rc;
+	unsigned int i;
 
 	if (!MACHINE_IS_VM) {
 		pr_info("The z/VM IUCV HVC device driver cannot "
@@ -901,14 +914,16 @@ static int __init hvc_iucv_init(void)
 
 	/* register the first terminal device as console
 	 * (must be done before allocating hvc terminal devices) */
-	rc = hvc_instantiate(HVC_IUCV_MAGIC, 0, &hvc_iucv_ops);
-	if (rc)
-		pr_warning("Registering HVC terminal device as "
-			   "Linux console failed\n");
+	rc = hvc_instantiate(HVC_IUCV_MAGIC, IUCV_HVC_CON_IDX, &hvc_iucv_ops);
+	if (rc) {
+		pr_err("Registering HVC terminal device as "
+		       "Linux console failed\n");
+		goto out_error_memory;
+	}
 
 	/* allocate hvc_iucv_private structs */
 	for (i = 0; i < hvc_iucv_devices; i++) {
-		rc = hvc_iucv_alloc(i);
+		rc = hvc_iucv_alloc(i, (i == IUCV_HVC_CON_IDX) ? 1 : 0);
 		if (rc) {
 			pr_err("Creating a new HVC terminal device "
 				"failed with error code=%d\n", rc);
@@ -935,6 +950,7 @@ out_error_hvc:
 				hvc_remove(hvc_iucv_table[i]->hvc);
 			kfree(hvc_iucv_table[i]);
 		}
+out_error_memory:
 	mempool_destroy(hvc_iucv_mempool);
 	kmem_cache_destroy(hvc_iucv_buffer_cache);
 	return rc;