From: Hans-Joachim Picht <hpicht@redhat.com>
Date: Thu, 12 Mar 2009 15:27:12 +0100
Subject: [s390] hvc_iucv: z/VM IUCV hypervisor console support
Message-id: 20090312142712.GS5103@redhat.com
O-Subject: [RHEL5 U4 PATCH 18/20] FEAT: s390 - hvc_iucv: z/VM IUCV hypervisor console (HVC) device driver support
Bugzilla: 475551

Description:
============

This patch provides a HVC back-end that supports terminal
connections over z/VM IUCV.

The device driver is always built-in.

To use this device driver, set the "hvc_iucv=" kernel parameter to
the number of terminal devices that should be used. The value is an
integer in the range 0 to 8. Specify 0 (default) to switch off the
device driver.

Bugzilla:
============
BZ  475551
https://bugzilla.redhat.com/show_bug.cgi?id=475551

Upstream status of the patch:
==============================

The patch is upstream.
linux-2.6.git commits:
6c089fd [S390] hvc_iucv: Special handling of IUCV HVC devices
68c6b3d [S390] hvc_iucv: Refactor console and device initialization
17e19f0 [S390] hvc_iucv: Update function documentation
c45ce4b [S390] hvc_iucv: Limit rate of outgoing IUCV messages
2dc184c [S390] hvc_iucv: Change IUCV term id and use one device
44a01d5 [S390] hvc_iucv: z/VM IUCV hypervisor console support

Test status:
============

The patch has been tested and fixes the problem.
The fix has been verified by the IBM test department.

Please ACK.

With best regards,

	--Hans

diff --git a/drivers/char/Makefile b/drivers/char/Makefile
index e126467..30563b5 100644
--- a/drivers/char/Makefile
+++ b/drivers/char/Makefile
@@ -44,7 +44,12 @@ obj-$(CONFIG_SX)		+= sx.o generic_serial.o
 obj-$(CONFIG_RIO)		+= rio/ generic_serial.o
 obj-$(CONFIG_HVC_CONSOLE)	+= hvc_vio.o hvsi.o
 obj-$(CONFIG_HVC_RTAS)		+= hvc_rtas.o
+ifeq ($(ARCH),s390)
+obj-$(CONFIG_HVC_DRIVER)	+= hvc_console_s390.o
+else
 obj-$(CONFIG_HVC_DRIVER)	+= hvc_console.o
+endif
+obj-$(CONFIG_HVC_IUCV)    += hvc_iucv.o
 obj-$(CONFIG_RAW_DRIVER)	+= raw.o
 obj-$(CONFIG_SGI_SNSC)		+= snsc.o snsc_event.o
 obj-$(CONFIG_MMTIMER)		+= mmtimer.o
diff --git a/drivers/char/hvc_iucv.c b/drivers/char/hvc_iucv.c
new file mode 100644
index 0000000..7b28044
--- /dev/null
+++ b/drivers/char/hvc_iucv.c
@@ -0,0 +1,1227 @@
+/*
+ * hvc_iucv.c - z/VM IUCV hypervisor console (HVC) device driver
+ *
+ * This HVC device driver provides terminal access using
+ * z/VM IUCV communication paths.
+ *
+ * Copyright IBM Corp. 2008
+ *
+ * Author(s):	Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
+ */
+#define KMSG_COMPONENT		"hvc_iucv"
+#define pr_fmt(fmt)		KMSG_COMPONENT ": " fmt
+
+#include <linux/types.h>
+#include <asm/ebcdic.h>
+#include <linux/ctype.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/mempool.h>
+#include <linux/moduleparam.h>
+#include <linux/tty.h>
+#include <linux/wait.h>
+#include <net/iucv/iucv.h>
+
+#include "hvc_console_s390.h"
+
+#ifndef pr_err
+#	define		pr_err(fmt,arg...) \
+				printk(KERN_ERR fmt,##arg)
+#endif
+
+
+/* General device driver settings */
+#define HVC_IUCV_MAGIC		0xc9e4c3e5
+#define MAX_HVC_IUCV_LINES	HVC_ALLOC_TTY_ADAPTERS
+#define MEMPOOL_MIN_NR		(PAGE_SIZE / sizeof(struct iucv_tty_buffer)/4)
+
+/* IUCV TTY message  */
+#define MSG_VERSION		0x02	/* Message version */
+#define MSG_TYPE_ERROR		0x01	/* Error message */
+#define MSG_TYPE_TERMENV	0x02	/* Terminal environment variable */
+#define MSG_TYPE_TERMIOS	0x04	/* Terminal IO struct update */
+#define MSG_TYPE_WINSIZE	0x08	/* Terminal window size update */
+#define MSG_TYPE_DATA		0x10	/* Terminal data */
+
+struct iucv_tty_msg {
+	u8	version;		/* Message version */
+	u8	type;			/* Message type */
+#define MSG_MAX_DATALEN		((u16)(~0))
+	u16	datalen;		/* Payload length */
+	u8	data[];			/* Payload buffer */
+} __attribute__((packed));
+#define MSG_SIZE(s)		((s) + offsetof(struct iucv_tty_msg, data))
+
+enum iucv_state_t {
+	IUCV_DISCONN	= 0,
+	IUCV_CONNECTED	= 1,
+	IUCV_SEVERED	= 2,
+};
+
+enum tty_state_t {
+	TTY_CLOSED	= 0,
+	TTY_OPENED	= 1,
+};
+
+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 */
+	spinlock_t		lock;		/* hvc_iucv_private lock */
+#define SNDBUF_SIZE		(PAGE_SIZE)	/* must be < MSG_MAX_DATALEN */
+	void			*sndbuf;	/* send buffer		  */
+	size_t			sndbuf_len;	/* length of send buffer  */
+#define QUEUE_SNDBUF_DELAY	(HZ / 25)
+	struct work_struct	sndbuf_work;	/* work: send iucv msg(s) */
+	wait_queue_head_t	sndbuf_waitq;	/* wait for send completion */
+	struct list_head	tty_outqueue;	/* outgoing IUCV messages */
+	struct list_head	tty_inqueue;	/* incoming IUCV messages */
+};
+
+struct iucv_tty_buffer {
+	struct list_head	list;	/* list pointer */
+	struct iucv_message	msg;	/* store an IUCV message */
+	size_t			offset;	/* data buffer offset */
+	struct iucv_tty_msg	*mbuf;	/* buffer to store input/output data */
+};
+
+/* IUCV callback handler */
+static	int hvc_iucv_path_pending(struct iucv_path *, u8[8], u8[16]);
+static void hvc_iucv_path_severed(struct iucv_path *, u8[16]);
+static void hvc_iucv_msg_pending(struct iucv_path *, struct iucv_message *);
+static void hvc_iucv_msg_complete(struct iucv_path *, struct iucv_message *);
+
+
+/* Kernel module parameter: use one terminal device as default */
+static unsigned long hvc_iucv_devices = 0;
+
+/* 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)
+/* List of z/VM user ID filter entries (struct iucv_vmid_filter) */
+#define MAX_VMID_FILTER		(500)
+static size_t hvc_iucv_filter_size;
+static void *hvc_iucv_filter;
+static const char *hvc_iucv_filter_string;
+static DEFINE_RWLOCK(hvc_iucv_filter_lock);
+
+/* Kmem cache and mempool for iucv_tty_buffer elements */
+static struct kmem_cache *hvc_iucv_buffer_cache;
+static mempool_t *hvc_iucv_mempool;
+
+/* IUCV handler callback functions */
+static struct iucv_handler hvc_iucv_handler = {
+	.path_pending  = hvc_iucv_path_pending,
+	.path_severed  = hvc_iucv_path_severed,
+	.message_complete = hvc_iucv_msg_complete,
+	.message_pending  = hvc_iucv_msg_pending,
+};
+
+
+/**
+ * hvc_iucv_get_private() - Return a struct hvc_iucv_private instance.
+ * @num:	The HVC virtual terminal number (vtermno)
+ *
+ * This function returns the struct hvc_iucv_private instance that corresponds
+ * to the HVC virtual terminal number specified as parameter @num.
+ */
+struct hvc_iucv_private *hvc_iucv_get_private(uint32_t num)
+{
+	if ((num < HVC_IUCV_MAGIC) || (num - HVC_IUCV_MAGIC > hvc_iucv_devices))
+		return NULL;
+	return hvc_iucv_table[num - HVC_IUCV_MAGIC];
+}
+
+/**
+ * alloc_tty_buffer() - Return a new struct iucv_tty_buffer element.
+ * @size:	Size of the internal buffer used to store data.
+ * @flags:	Memory allocation flags passed to mempool.
+ *
+ * This function allocates a new struct iucv_tty_buffer element and, optionally,
+ * allocates an internal data buffer with the specified size @size.
+ * Note: The total message size arises from the internal buffer size and the
+ *	 members of the iucv_tty_msg structure.
+ * The function returns NULL if memory allocation has failed.
+ */
+static struct iucv_tty_buffer *alloc_tty_buffer(size_t size, gfp_t flags)
+{
+	struct iucv_tty_buffer *bufp;
+
+	bufp = mempool_alloc(hvc_iucv_mempool, flags);
+	if (!bufp)
+		return NULL;
+	memset(bufp, 0, sizeof(*bufp));
+
+	if (size > 0) {
+		bufp->msg.length = MSG_SIZE(size);
+		bufp->mbuf = kmalloc(bufp->msg.length, flags);
+		if (!bufp->mbuf) {
+			mempool_free(bufp, hvc_iucv_mempool);
+			return NULL;
+		}
+		bufp->mbuf->version = MSG_VERSION;
+		bufp->mbuf->type    = MSG_TYPE_DATA;
+		bufp->mbuf->datalen = (u16) size;
+	}
+	return bufp;
+}
+
+/**
+ * destroy_tty_buffer() - destroy struct iucv_tty_buffer element.
+ * @bufp:	Pointer to a struct iucv_tty_buffer element, SHALL NOT be NULL.
+ */
+static void destroy_tty_buffer(struct iucv_tty_buffer *bufp)
+{
+	kfree(bufp->mbuf);
+	mempool_free(bufp, hvc_iucv_mempool);
+}
+
+/**
+ * destroy_tty_buffer_list() - call destroy_tty_buffer() for each list element.
+ * @list:	List containing struct iucv_tty_buffer elements.
+ */
+static void destroy_tty_buffer_list(struct list_head *list)
+{
+	struct iucv_tty_buffer *ent, *next;
+
+	list_for_each_entry_safe(ent, next, list, list) {
+		list_del(&ent->list);
+		destroy_tty_buffer(ent);
+	}
+}
+
+/**
+ * hvc_iucv_write() - Receive IUCV message & write data to HVC buffer.
+ * @priv:		Pointer to struct hvc_iucv_private
+ * @buf:		HVC buffer for writing received terminal data.
+ * @count:		HVC buffer size.
+ * @has_more_data:	Pointer to an int variable.
+ *
+ * The function picks up pending messages from the input queue and receives
+ * the message data that is then written to the specified buffer @buf.
+ * If the buffer size @count is less than the data message size, the
+ * message is kept on the input queue and @has_more_data is set to 1.
+ * If all message data has been written, the message is removed from
+ * the input queue.
+ *
+ * The function returns the number of bytes written to the terminal, zero if
+ * there are no pending data messages available or if there is no established
+ * IUCV path.
+ * If the IUCV path has been severed, then -EPIPE is returned to cause a
+ * hang up (that is issued by the HVC layer).
+ */
+static int hvc_iucv_write(struct hvc_iucv_private *priv,
+			  char *buf, int count, int *has_more_data)
+{
+	struct iucv_tty_buffer *rb;
+	int written;
+	int rc;
+
+	/* immediately return if there is no IUCV connection */
+	if (priv->iucv_state == IUCV_DISCONN)
+		return 0;
+
+	/* if the IUCV path has been severed, return -EPIPE to inform the
+	 * HVC layer to hang up the tty device. */
+	if (priv->iucv_state == IUCV_SEVERED)
+		return -EPIPE;
+
+	/* check if there are pending messages */
+	if (list_empty(&priv->tty_inqueue))
+		return 0;
+
+	/* receive an iucv message and flip data to the tty (ldisc) */
+	rb = list_first_entry(&priv->tty_inqueue, struct iucv_tty_buffer, list);
+
+	written = 0;
+	if (!rb->mbuf) { /* message not yet received ... */
+		/* allocate mem to store msg data; if no memory is available
+		 * then leave the buffer on the list and re-try later */
+		rb->mbuf = kmalloc(rb->msg.length, GFP_ATOMIC);
+		if (!rb->mbuf)
+			return -ENOMEM;
+
+		rc = __iucv_message_receive(priv->path, &rb->msg, 0,
+					    rb->mbuf, rb->msg.length, NULL);
+		switch (rc) {
+		case 0: /* Successful	    */
+			break;
+		case 2:	/* No message found */
+		case 9: /* Message purged   */
+			break;
+		default:
+			written = -EIO;
+		}
+		/* remove buffer if an error has occured or received data
+		 * is not correct */
+		if (rc || (rb->mbuf->version != MSG_VERSION) ||
+			  (rb->msg.length    != MSG_SIZE(rb->mbuf->datalen)))
+			goto out_remove_buffer;
+	}
+
+	switch (rb->mbuf->type) {
+	case MSG_TYPE_DATA:
+		written = min_t(int, rb->mbuf->datalen - rb->offset, count);
+		memcpy(buf, rb->mbuf->data + rb->offset, written);
+		if (written < (rb->mbuf->datalen - rb->offset)) {
+			rb->offset += written;
+			*has_more_data = 1;
+			goto out_written;
+		}
+		break;
+
+	case MSG_TYPE_WINSIZE:
+		if (rb->mbuf->datalen != sizeof(struct winsize))
+			break;
+		hvc_resize(priv->hvc, *((struct winsize *) rb->mbuf->data));
+		break;
+
+	case MSG_TYPE_ERROR:	/* ignored ... */
+	case MSG_TYPE_TERMENV:	/* ignored ... */
+	case MSG_TYPE_TERMIOS:	/* ignored ... */
+		break;
+	}
+
+out_remove_buffer:
+	list_del(&rb->list);
+	destroy_tty_buffer(rb);
+	*has_more_data = !list_empty(&priv->tty_inqueue);
+
+out_written:
+	return written;
+}
+
+/**
+ * hvc_iucv_get_chars() - HVC get_chars operation.
+ * @vtermno:	HVC virtual terminal number.
+ * @buf:	Pointer to a buffer to store data
+ * @count:	Size of buffer available for writing
+ *
+ * The HVC thread calls this method to read characters from the back-end.
+ * If an IUCV communication path has been established, pending IUCV messages
+ * are received and data is copied into buffer @buf up to @count bytes.
+ *
+ * Locking:	The routine gets called under an irqsave() spinlock; and
+ *		the routine locks the struct hvc_iucv_private->lock to call
+ *		helper functions.
+ */
+static int hvc_iucv_get_chars(uint32_t vtermno, char *buf, int count)
+{
+	struct hvc_iucv_private *priv = hvc_iucv_get_private(vtermno);
+	int written;
+	int has_more_data;
+
+	if (count <= 0)
+		return 0;
+
+	if (!priv)
+		return -ENODEV;
+
+	spin_lock(&priv->lock);
+	has_more_data = 0;
+	written = hvc_iucv_write(priv, buf, count, &has_more_data);
+	spin_unlock(&priv->lock);
+
+	/* if there are still messages on the queue... schedule another run */
+	if (has_more_data)
+		hvc_kick();
+
+	return written;
+}
+
+/**
+ * hvc_iucv_queue() - Buffer terminal data for sending.
+ * @priv:	Pointer to struct hvc_iucv_private instance.
+ * @buf:	Buffer containing data to send.
+ * @count:	Size of buffer and amount of data to send.
+ *
+ * The function queues data for sending. To actually send the buffered data,
+ * a work queue function is scheduled (with QUEUE_SNDBUF_DELAY).
+ * The function returns the number of data bytes that has been buffered.
+ *
+ * If the device is not connected, data is ignored and the function returns
+ * @count.
+ * If the buffer is full, the function returns 0.
+ * If an existing IUCV communicaton path has been severed, -EPIPE is returned
+ * (that can be passed to HVC layer to cause a tty hangup).
+ */
+static int hvc_iucv_queue(struct hvc_iucv_private *priv, const char *buf,
+			  int count)
+{
+	size_t len;
+
+	if (priv->iucv_state == IUCV_DISCONN)
+		return count;			/* ignore data */
+
+	if (priv->iucv_state == IUCV_SEVERED)
+		return -EPIPE;
+
+	len = min_t(size_t, count, SNDBUF_SIZE - priv->sndbuf_len);
+	if (!len)
+		return 0;
+
+	memcpy(priv->sndbuf + priv->sndbuf_len, buf, len);
+	priv->sndbuf_len += len;
+
+	if (priv->iucv_state == IUCV_CONNECTED)
+		schedule_delayed_work(&priv->sndbuf_work, QUEUE_SNDBUF_DELAY);
+
+	return len;
+}
+
+/**
+ * hvc_iucv_send() - Send an IUCV message containing terminal data.
+ * @priv:	Pointer to struct hvc_iucv_private instance.
+ *
+ * If an IUCV communication path has been established, the buffered output data
+ * is sent via an IUCV message and the number of bytes sent is returned.
+ * Returns 0 if there is no established IUCV communication path or
+ * -EPIPE if an existing IUCV communicaton path has been severed.
+ */
+static int hvc_iucv_send(struct hvc_iucv_private *priv)
+{
+	struct iucv_tty_buffer *sb;
+	int rc, len;
+
+	if (priv->iucv_state == IUCV_SEVERED)
+		return -EPIPE;
+
+	if (priv->iucv_state == IUCV_DISCONN)
+		return -EIO;
+
+	if (!priv->sndbuf_len)
+		return 0;
+
+	/* allocate internal buffer to store msg data and also compute total
+	 * message length */
+	sb = alloc_tty_buffer(priv->sndbuf_len, GFP_ATOMIC);
+	if (!sb)
+		return -ENOMEM;
+
+	memcpy(sb->mbuf->data, priv->sndbuf, priv->sndbuf_len);
+	sb->mbuf->datalen = (u16) priv->sndbuf_len;
+	sb->msg.length = MSG_SIZE(sb->mbuf->datalen);
+
+	list_add_tail(&sb->list, &priv->tty_outqueue);
+
+	rc = __iucv_message_send(priv->path, &sb->msg, 0, 0,
+				 (void *) sb->mbuf, sb->msg.length);
+	if (rc) {
+		/* drop the message here; however we might want to handle
+		 * 0x03 (msg limit reached) by trying again... */
+		list_del(&sb->list);
+		destroy_tty_buffer(sb);
+	}
+	len = priv->sndbuf_len;
+	priv->sndbuf_len = 0;
+
+	return len;
+}
+
+/**
+ * hvc_iucv_sndbuf_work() - Send buffered data over IUCV
+ * @work:	Work structure.
+ *
+ * This work queue function sends buffered output data over IUCV and,
+ * if not all buffered data could be sent, reschedules itself.
+ */
+static void hvc_iucv_sndbuf_work(void *data)
+{
+	struct hvc_iucv_private *priv;
+
+	priv = (struct hvc_iucv_private *) data;
+	if (!priv)
+		return;
+
+	spin_lock_bh(&priv->lock);
+	hvc_iucv_send(priv);
+	spin_unlock_bh(&priv->lock);
+}
+
+/**
+ * hvc_iucv_put_chars() - HVC put_chars operation.
+ * @vtermno:	HVC virtual terminal number.
+ * @buf:	Pointer to an buffer to read data from
+ * @count:	Size of buffer available for reading
+ *
+ * The HVC thread calls this method to write characters to the back-end.
+ * The function calls hvc_iucv_queue() to queue terminal data for sending.
+ *
+ * Locking:	The method gets called under an irqsave() spinlock; and
+ *		locks struct hvc_iucv_private->lock.
+ */
+static int hvc_iucv_put_chars(uint32_t vtermno, const char *buf, int count)
+{
+	struct hvc_iucv_private *priv = hvc_iucv_get_private(vtermno);
+	int queued;
+
+	if (count <= 0)
+		return 0;
+
+	if (!priv)
+		return -ENODEV;
+
+	spin_lock(&priv->lock);
+	queued = hvc_iucv_queue(priv, buf, count);
+	spin_unlock(&priv->lock);
+
+	return queued;
+}
+
+/**
+ * hvc_iucv_notifier_add() - HVC notifier for opening a TTY for the first time.
+ * @hp:	Pointer to the HVC device (struct hvc_struct)
+ * @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_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
+ */
+static int hvc_iucv_notifier_add(struct hvc_struct *hp, int id)
+{
+	struct hvc_iucv_private *priv;
+
+	priv = hvc_iucv_get_private(id);
+	if (!priv)
+		return 0;
+
+	spin_lock_bh(&priv->lock);
+	priv->tty_state = TTY_OPENED;
+	spin_unlock_bh(&priv->lock);
+
+	return 0;
+}
+
+/**
+ * hvc_iucv_cleanup() - Clean up and reset a z/VM IUCV HVC instance.
+ * @priv:	Pointer to the struct hvc_iucv_private instance.
+ */
+static void hvc_iucv_cleanup(struct hvc_iucv_private *priv)
+{
+	destroy_tty_buffer_list(&priv->tty_outqueue);
+	destroy_tty_buffer_list(&priv->tty_inqueue);
+
+	priv->tty_state = TTY_CLOSED;
+	priv->iucv_state = IUCV_DISCONN;
+
+	priv->sndbuf_len = 0;
+}
+
+/**
+ * tty_outqueue_empty() - Test if the tty outq is empty
+ * @priv:	Pointer to struct hvc_iucv_private instance.
+ */
+static inline int tty_outqueue_empty(struct hvc_iucv_private *priv)
+{
+	int rc;
+
+	spin_lock_bh(&priv->lock);
+	rc = list_empty(&priv->tty_outqueue);
+	spin_unlock_bh(&priv->lock);
+
+	return rc;
+}
+
+/**
+ * flush_sndbuf_sync() - Flush send buffer and wait for completion
+ * @priv:	Pointer to struct hvc_iucv_private instance.
+ *
+ * The routine cancels a pending sndbuf work, calls hvc_iucv_send()
+ * to flush any buffered terminal output data and waits for completion.
+ */
+static void flush_sndbuf_sync(struct hvc_iucv_private *priv)
+{
+	int sync_wait;
+
+	cancel_delayed_work(&priv->sndbuf_work);
+
+	spin_lock_bh(&priv->lock);
+	hvc_iucv_send(priv);		/* force sending buffered data */
+	sync_wait = !list_empty(&priv->tty_outqueue); /* anything queued ? */
+	spin_unlock_bh(&priv->lock);
+
+	if (sync_wait)
+		wait_event_timeout(priv->sndbuf_waitq,
+				   tty_outqueue_empty(priv), HZ);
+}
+
+/**
+ * hvc_iucv_notifier_hangup() - HVC notifier for TTY hangups.
+ * @hp:		Pointer to the HVC device (struct hvc_struct)
+ * @id:		Additional data (originally passed to hvc_alloc):
+ *		the index of an struct hvc_iucv_private instance.
+ *
+ * This routine notifies the HVC back-end that a tty hangup (carrier loss,
+ * virtual or otherwise) has occured.
+ * The z/VM IUCV HVC device driver ignores virtual hangups (vhangup())
+ * to keep an existing IUCV communication path established.
+ * (Background: vhangup() is called from user space (by getty or login) to
+ *		disable writing to the tty by other applications).
+ * If the tty has been opened and an established IUCV path has been severed
+ * (we caused the tty hangup), the function calls hvc_iucv_cleanup().
+ *
+ * Locking:	struct hvc_iucv_private->lock
+ */
+static void hvc_iucv_notifier_hangup(struct hvc_struct *hp, int id)
+{
+	struct hvc_iucv_private *priv;
+
+	priv = hvc_iucv_get_private(id);
+	if (!priv)
+		return;
+
+	flush_sndbuf_sync(priv);
+
+	spin_lock_bh(&priv->lock);
+	/* NOTE: If the hangup was scheduled by ourself (from the iucv
+	 *	 path_servered callback [IUCV_SEVERED]), we have to clean up
+	 *	 our structure and to set state to TTY_CLOSED.
+	 *	 If the tty was hung up otherwise (e.g. vhangup()), then we
+	 *	 ignore this hangup and keep an established IUCV path open...
+	 *	 (...the reason is that we are not able to connect back to the
+	 *	 client if we disconnect on hang up) */
+	priv->tty_state = TTY_CLOSED;
+
+	if (priv->iucv_state == IUCV_SEVERED)
+		hvc_iucv_cleanup(priv);
+	spin_unlock_bh(&priv->lock);
+}
+
+/**
+ * hvc_iucv_notifier_del() - HVC notifier for closing a TTY for the last time.
+ * @hp:		Pointer to the HVC device (struct hvc_struct)
+ * @id:		Additional data (originally passed to hvc_alloc):
+ *		the index of an struct hvc_iucv_private instance.
+ *
+ * This routine notifies the HVC back-end that the last tty device fd has been
+ * closed.  The function calls hvc_iucv_cleanup() to clean up the struct
+ * hvc_iucv_private instance.
+ *
+ * Locking:	struct hvc_iucv_private->lock
+ */
+static void hvc_iucv_notifier_del(struct hvc_struct *hp, int id)
+{
+	struct hvc_iucv_private *priv;
+	struct iucv_path	*path;
+
+	priv = hvc_iucv_get_private(id);
+	if (!priv)
+		return;
+
+	flush_sndbuf_sync(priv);
+
+	spin_lock_bh(&priv->lock);
+	path = priv->path;		/* save reference to IUCV path */
+	priv->path = NULL;
+	hvc_iucv_cleanup(priv);
+	spin_unlock_bh(&priv->lock);
+
+	/* sever IUCV path outside of priv->lock due to lock ordering of:
+	 * priv->lock <--> iucv_table_lock */
+	if (path) {
+		iucv_path_sever(path, NULL);
+		iucv_path_free(path);
+	}
+}
+
+/**
+ * hvc_iucv_filter_connreq() - Filter connection request based on z/VM user ID
+ * @ipvmid:	Originating z/VM user ID (right padded with blanks)
+ *
+ * Returns 0 if the z/VM user ID @ipvmid is allowed to connection, otherwise
+ * non-zero.
+ */
+static int hvc_iucv_filter_connreq(u8 ipvmid[8])
+{
+	size_t i;
+
+	/* Note: default policy is ACCEPT if no filter is set */
+	if (!hvc_iucv_filter_size)
+		return 0;
+
+	for (i = 0; i < hvc_iucv_filter_size; i++)
+		if (0 == memcmp(ipvmid, hvc_iucv_filter + (8 * i), 8))
+			return 0;
+	return 1;
+}
+
+/**
+ * hvc_iucv_path_pending() - IUCV handler to process a connection request.
+ * @path:	Pending path (struct iucv_path)
+ * @ipvmid:	z/VM system identifier of originator
+ * @ipuser:	User specified data for this path
+ *		(AF_IUCV: port/service name and originator port)
+ *
+ * The function uses the @ipuser data to determine if the pending path belongs
+ * to a terminal managed by this device driver.
+ * If the path belongs to this driver, ensure that the terminal is not accessed
+ * multiple times (only one connection to a terminal is allowed).
+ * If the terminal is not yet connected, the pending path is accepted and is
+ * associated to the appropriate struct hvc_iucv_private instance.
+ *
+ * Returns 0 if @path belongs to a terminal managed by the this device driver;
+ * otherwise returns -ENODEV in order to dispatch this path to other handlers.
+ *
+ * Locking:	struct hvc_iucv_private->lock
+ */
+static	int hvc_iucv_path_pending(struct iucv_path *path,
+				  u8 ipvmid[8], u8 ipuser[16])
+{
+	struct hvc_iucv_private *priv;
+	u8 nuser_data[16];
+	u8 vm_user_id[9];
+	int i, rc;
+
+	priv = NULL;
+	for (i = 0; i < hvc_iucv_devices; i++)
+		if (hvc_iucv_table[i] &&
+		    (0 == memcmp(hvc_iucv_table[i]->srv_name, ipuser, 8))) {
+			priv = hvc_iucv_table[i];
+			break;
+		}
+	if (!priv)
+		return -ENODEV;
+
+	/* Enforce that ipvmid is allowed to connect to us */
+	read_lock(&hvc_iucv_filter_lock);
+	rc = hvc_iucv_filter_connreq(ipvmid);
+	read_unlock(&hvc_iucv_filter_lock);
+	if (rc) {
+		iucv_path_sever(path, ipuser);
+		iucv_path_free(path);
+		memcpy(vm_user_id, ipvmid, 8);
+		vm_user_id[8] = 0;
+		pr_info("A connection request from z/VM user ID %s "
+			"was refused\n", vm_user_id);
+		return 0;
+	}
+
+	spin_lock(&priv->lock);
+
+	/* If the terminal is already connected or being severed, then sever
+	 * this path to enforce that there is only ONE established communication
+	 * path per terminal. */
+	if (priv->iucv_state != IUCV_DISCONN) {
+		iucv_path_sever(path, ipuser);
+		iucv_path_free(path);
+		goto out_path_handled;
+	}
+
+	/* accept path */
+	memcpy(nuser_data, ipuser + 8, 8);  /* remote service (for af_iucv) */
+	memcpy(nuser_data + 8, ipuser, 8);  /* local service  (for af_iucv) */
+	path->msglim = 0xffff;		    /* IUCV MSGLIMIT */
+	path->flags &= ~IUCV_IPRMDATA;	    /* TODO: use IUCV_IPRMDATA */
+	rc = iucv_path_accept(path, &hvc_iucv_handler, nuser_data, priv);
+	if (rc) {
+		iucv_path_sever(path, ipuser);
+		iucv_path_free(path);
+		goto out_path_handled;
+	}
+	priv->path = path;
+	priv->iucv_state = IUCV_CONNECTED;
+
+	/* flush buffered output data... */
+	schedule_delayed_work(&priv->sndbuf_work, 5);
+
+out_path_handled:
+	spin_unlock(&priv->lock);
+	return 0;
+}
+
+/**
+ * hvc_iucv_path_severed() - IUCV handler to process a path sever.
+ * @path:	Pending path (struct iucv_path)
+ * @ipuser:	User specified data for this path
+ *		(AF_IUCV: port/service name and originator port)
+ *
+ * The function also severs the path (as required by the IUCV protocol) and
+ * sets the iucv state to IUCV_SEVERED for the associated struct
+ * hvc_iucv_private instance. Later, the IUCV_SEVERED state triggers a tty
+ * hangup (hvc_iucv_get_chars() / hvc_iucv_write()).
+ * If tty portion of the HVC is closed, clean up the outqueue.
+ *
+ * Locking:	struct hvc_iucv_private->lock
+ */
+static void hvc_iucv_path_severed(struct iucv_path *path, u8 ipuser[16])
+{
+	struct hvc_iucv_private *priv = path->private;
+
+	spin_lock(&priv->lock);
+	priv->iucv_state = IUCV_SEVERED;
+
+	/* 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.
+	 * If so, we need to wake up the HVC thread to call get_chars()...
+	 */
+	priv->path = NULL;
+	if (priv->tty_state == TTY_CLOSED)
+		hvc_iucv_cleanup(priv);
+	else
+		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) */
+	iucv_path_sever(path, ipuser);
+	iucv_path_free(path);
+}
+
+/**
+ * hvc_iucv_msg_pending() - IUCV handler to process an incoming IUCV message.
+ * @path:	Pending path (struct iucv_path)
+ * @msg:	Pointer to the IUCV message
+ *
+ * The function puts an incoming message on the input queue for later
+ * processing (by hvc_iucv_get_chars() / hvc_iucv_write()).
+ * If the tty has not yet been opened, the message is rejected.
+ *
+ * Locking:	struct hvc_iucv_private->lock
+ */
+static void hvc_iucv_msg_pending(struct iucv_path *path,
+				 struct iucv_message *msg)
+{
+	struct hvc_iucv_private *priv = path->private;
+	struct iucv_tty_buffer *rb;
+
+	/* reject messages that exceed max size of iucv_tty_msg->datalen */
+	if (msg->length > MSG_SIZE(MSG_MAX_DATALEN)) {
+		iucv_message_reject(path, msg);
+		return;
+	}
+
+	spin_lock(&priv->lock);
+
+	/* reject messages if tty has not yet been opened */
+	if (priv->tty_state == TTY_CLOSED) {
+		iucv_message_reject(path, msg);
+		goto unlock_return;
+	}
+
+	/* allocate tty buffer to save iucv msg only */
+	rb = alloc_tty_buffer(0, GFP_ATOMIC);
+	if (!rb) {
+		iucv_message_reject(path, msg);
+		goto unlock_return;	/* -ENOMEM */
+	}
+	rb->msg = *msg;
+
+	list_add_tail(&rb->list, &priv->tty_inqueue);
+
+	hvc_kick();	/* wake up hvc thread */
+
+unlock_return:
+	spin_unlock(&priv->lock);
+}
+
+/**
+ * hvc_iucv_msg_complete() - IUCV handler to process message completion
+ * @path:	Pending path (struct iucv_path)
+ * @msg:	Pointer to the IUCV message
+ *
+ * The function is called upon completion of message delivery to remove the
+ * message from the outqueue. Additional delivery information can be found
+ * msg->audit: rejected messages (0x040000 (IPADRJCT)), and
+ *	       purged messages	 (0x010000 (IPADPGNR)).
+ *
+ * Locking:	struct hvc_iucv_private->lock
+ */
+static void hvc_iucv_msg_complete(struct iucv_path *path,
+				  struct iucv_message *msg)
+{
+	struct hvc_iucv_private *priv = path->private;
+	struct iucv_tty_buffer	*ent, *next;
+	LIST_HEAD(list_remove);
+
+	spin_lock(&priv->lock);
+	list_for_each_entry_safe(ent, next, &priv->tty_outqueue, list)
+		if (ent->msg.id == msg->id) {
+			list_move(&ent->list, &list_remove);
+			break;
+		}
+	wake_up(&priv->sndbuf_waitq);
+	spin_unlock(&priv->lock);
+	destroy_tty_buffer_list(&list_remove);
+}
+
+
+/* HVC operations */
+static struct hv_ops hvc_iucv_ops = {
+	.get_chars = hvc_iucv_get_chars,
+	.put_chars = hvc_iucv_put_chars,
+	.notifier_add = hvc_iucv_notifier_add,
+	.notifier_del = hvc_iucv_notifier_del,
+	.notifier_hangup = hvc_iucv_notifier_hangup,
+};
+
+/**
+ * hvc_iucv_alloc() - Allocates a new struct hvc_iucv_private instance
+ * @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, unsigned int is_console)
+{
+	struct hvc_iucv_private *priv;
+	char name[9];
+	int rc;
+
+	priv = kzalloc(sizeof(struct hvc_iucv_private), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	spin_lock_init(&priv->lock);
+	INIT_LIST_HEAD(&priv->tty_outqueue);
+	INIT_LIST_HEAD(&priv->tty_inqueue);
+	INIT_WORK(&priv->sndbuf_work, hvc_iucv_sndbuf_work, priv);
+	init_waitqueue_head(&priv->sndbuf_waitq);
+
+	priv->sndbuf = (void *) get_zeroed_page(GFP_KERNEL);
+	if (!priv->sndbuf) {
+		kfree(priv);
+		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);
+	if (IS_ERR(priv->hvc)) {
+		rc = PTR_ERR(priv->hvc);
+		free_page((unsigned long) priv->sndbuf);
+		kfree(priv);
+		return rc;
+	}
+
+	/* notify HVC thread instead of using polling */
+	priv->hvc->irq_requested = 1;
+
+	/* setup iucv related information */
+	snprintf(name, 9, "lnxhvc%-2d", id);
+	memcpy(priv->srv_name, name, 8);
+	ASCEBC(priv->srv_name, 8);
+
+	hvc_iucv_table[id] = priv;
+	return 0;
+}
+
+/**
+ * hvc_iucv_parse_filter() - Parse filter for a single z/VM user ID
+ * @filter:	String containing a comma-separated list of z/VM user IDs
+ */
+static const char *hvc_iucv_parse_filter(const char *filter, char *dest)
+{
+	const char *nextdelim, *residual;
+	size_t len;
+
+	nextdelim = strchr(filter, ',');
+	if (nextdelim) {
+		len = nextdelim - filter;
+		residual = nextdelim + 1;
+	} else {
+		len = strlen(filter);
+		residual = filter + len;
+	}
+
+	if (len == 0)
+		return ERR_PTR(-EINVAL);
+
+	/* check for '\n' (if called from sysfs) */
+	if (filter[len - 1] == '\n')
+		len--;
+
+	if (len > 8)
+		return ERR_PTR(-EINVAL);
+
+	/* pad with blanks and save upper case version of user ID */
+	memset(dest, ' ', 8);
+	while (len--)
+		dest[len] = toupper(filter[len]);
+	return residual;
+}
+
+/**
+ * hvc_iucv_setup_filter() - Set up z/VM user ID filter
+ * @filter:	String consisting of a comma-separated list of z/VM user IDs
+ *
+ * The function parses the @filter string and creates an array containing
+ * the list of z/VM user ID filter entries.
+ * Return code 0 means success, -EINVAL if the filter is syntactically
+ * incorrect, -ENOMEM if there was not enough memory to allocate the
+ * filter list array, or -ENOSPC if too many z/VM user IDs have been specified.
+ */
+static int hvc_iucv_setup_filter(const char *val)
+{
+	const char *residual;
+	int err;
+	size_t size, count;
+	void *array, *old_filter;
+
+	count = strlen(val);
+	if (count == 0 || (count == 1 && val[0] == '\n')) {
+		size  = 0;
+		array = NULL;
+		goto out_replace_filter;	/* clear filter */
+	}
+
+	/* count user IDs in order to allocate sufficient memory */
+	size = 1;
+	residual = val;
+	while ((residual = strchr(residual, ',')) != NULL) {
+		residual++;
+		size++;
+	}
+
+	/* check if the specified list exceeds the filter limit */
+	if (size > MAX_VMID_FILTER)
+		return -ENOSPC;
+
+	array = kzalloc(size * 8, GFP_KERNEL);
+	if (!array)
+		return -ENOMEM;
+
+	count = size;
+	residual = val;
+	while (*residual && count) {
+		residual = hvc_iucv_parse_filter(residual,
+						 array + ((size - count) * 8));
+		if (IS_ERR(residual)) {
+			err = PTR_ERR(residual);
+			kfree(array);
+			goto out_err;
+		}
+		count--;
+	}
+
+out_replace_filter:
+	write_lock_bh(&hvc_iucv_filter_lock);
+	old_filter = hvc_iucv_filter;
+	hvc_iucv_filter_size = size;
+	hvc_iucv_filter = array;
+	write_unlock_bh(&hvc_iucv_filter_lock);
+	kfree(old_filter);
+
+	err = 0;
+out_err:
+	return err;
+}
+
+/**
+ * param_set_vmidfilter() - Set z/VM user ID filter parameter
+ * @val:	String consisting of a comma-separated list of z/VM user IDs
+ * @kp:		Kernel parameter pointing to hvc_iucv_filter array
+ *
+ * The function sets up the z/VM user ID filter specified as comma-separated
+ * list of user IDs in @val.
+ * Note: If it is called early in the boot process, @val is stored and
+ *	 parsed later in hvc_iucv_init().
+ */
+static int param_set_vmidfilter(const char *val, struct kernel_param *kp)
+{
+	int rc;
+
+	if (!MACHINE_IS_VM || !hvc_iucv_devices)
+		return -ENODEV;
+
+	if (!val)
+		return -EINVAL;
+
+	rc = 0;
+	if (slab_is_available())
+		rc = hvc_iucv_setup_filter(val);
+	else
+		hvc_iucv_filter_string = val;	/* defer... */
+	return rc;
+}
+
+/**
+ * param_get_vmidfilter() - Get z/VM user ID filter
+ * @buffer:	Buffer to store z/VM user ID filter,
+ * 		(buffer size assumption PAGE_SIZE)
+ * @kp:		Kernel parameter pointing to the hvc_iucv_filter array
+ *
+ * The function stores the filter as a comma-separated list of z/VM user IDs
+ * in @buffer. Typically, sysfs routines call this function for attr show.
+ */
+static int param_get_vmidfilter(char *buffer, struct kernel_param *kp)
+{
+	int rc;
+	size_t index, len;
+	void *start, *end;
+
+	if (!MACHINE_IS_VM || !hvc_iucv_devices)
+		return -ENODEV;
+
+	rc = 0;
+	read_lock_bh(&hvc_iucv_filter_lock);
+	for (index = 0; index < hvc_iucv_filter_size; index++) {
+		start = hvc_iucv_filter + (8 * index);
+		end   = memchr(start, ' ', 8);
+		len   = (end) ? end - start : 8;
+		memcpy(buffer + rc, start, len);
+		rc += len;
+		buffer[rc++] = ',';
+	}
+	read_unlock_bh(&hvc_iucv_filter_lock);
+	if (rc)
+		buffer[--rc] = '\0';	/* replace last comma and update rc */
+	return rc;
+}
+
+#define param_check_vmidfilter(name, p) __param_check(name, p, void)
+
+/**
+ * hvc_iucv_init() - z/VM IUCV HVC device driver initialization
+ */
+static int __init hvc_iucv_init(void)
+{
+	int rc;
+	unsigned int i;
+
+	if (!hvc_iucv_devices)
+		return -ENODEV;
+
+	if (!MACHINE_IS_VM) {
+		pr_info("The z/VM IUCV HVC device driver cannot "
+			   "be used without z/VM\n");
+		rc = -ENODEV;
+		goto out_error;
+	}
+
+	if (hvc_iucv_devices > MAX_HVC_IUCV_LINES) {
+		pr_err("%lu is not a valid value for the hvc_iucv= "
+			"kernel parameter\n", hvc_iucv_devices);
+		rc = -EINVAL;
+		goto out_error;
+	}
+
+	/* parse hvc_iucv_allow string and create z/VM user ID filter list */
+	if (hvc_iucv_filter_string) {
+		rc = hvc_iucv_setup_filter(hvc_iucv_filter_string);
+		switch (rc) {
+		case 0:
+			break;
+		case -ENOMEM:
+			pr_err("Allocating memory failed with "
+				"reason code=%d\n", 3);
+			goto out_error;
+		case -EINVAL:
+			pr_err("hvc_iucv_allow= does not specify a valid "
+				"z/VM user ID list\n");
+			goto out_error;
+		case -ENOSPC:
+			pr_err("hvc_iucv_allow= specifies too many "
+				"z/VM user IDs\n");
+			goto out_error;
+		default:
+			goto out_error;
+		}
+	}
+
+	hvc_iucv_buffer_cache = kmem_cache_create(KMSG_COMPONENT,
+					   sizeof(struct iucv_tty_buffer),
+					   0, 0, NULL, NULL);
+	if (!hvc_iucv_buffer_cache) {
+		pr_err("Allocating memory failed with reason code=%d\n", 1);
+		rc = -ENOMEM;
+		goto out_error;
+	}
+
+	hvc_iucv_mempool = mempool_create_slab_pool(MEMPOOL_MIN_NR,
+						    hvc_iucv_buffer_cache);
+	if (!hvc_iucv_mempool) {
+		pr_err("Allocating memory failed with reason code=%d\n", 2);
+		kmem_cache_destroy(hvc_iucv_buffer_cache);
+		rc = -ENOMEM;
+		goto out_error;
+	}
+
+	/* register the first terminal device as console
+	 * (must be done before allocating hvc terminal devices) */
+	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, (i == IUCV_HVC_CON_IDX) ? 1 : 0);
+		if (rc) {
+			pr_err("Creating a new HVC terminal device "
+				"failed with error code=%d\n", rc);
+			goto out_error_hvc;
+		}
+	}
+
+	/* register IUCV callback handler */
+	rc = iucv_register(&hvc_iucv_handler, 0);
+	if (rc) {
+		pr_err("Registering IUCV handlers failed with error code=%d\n",
+			rc);
+		goto out_error_iucv;
+	}
+
+	return 0;
+
+out_error_iucv:
+	iucv_unregister(&hvc_iucv_handler, 0);
+out_error_hvc:
+	for (i = 0; i < hvc_iucv_devices; i++)
+		if (hvc_iucv_table[i]) {
+			if (hvc_iucv_table[i]->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);
+out_error:
+	hvc_iucv_devices = 0; /* ensure that we do not provide any device */
+	return rc;
+}
+
+/**
+ * hvc_iucv_config() - Parsing of hvc_iucv=  kernel command line parameter
+ * @val:	Parameter value (numeric)
+ */
+static int __init hvc_iucv_config(char *val)
+{
+	hvc_iucv_devices = simple_strtoul(val, NULL, 10);
+	return 0;
+}
+
+/**
+ * Backport: core_param() is not yet available, use module_param_named()
+ * instead and provide a function for __setup()
+ */
+static int __init hvc_iucv_allow_config(char *val)
+{
+	return param_set_vmidfilter(val, NULL);
+}
+
+
+device_initcall(hvc_iucv_init);
+__setup("hvc_iucv=", hvc_iucv_config);
+__setup("hvc_iucv_allow=", hvc_iucv_allow_config);
+module_param_named(hvc_iucv_allow, hvc_iucv_filter, vmidfilter, 0640);
diff --git a/drivers/s390/Kconfig b/drivers/s390/Kconfig
index 69c34c5..b9271e3 100644
--- a/drivers/s390/Kconfig
+++ b/drivers/s390/Kconfig
@@ -62,6 +62,24 @@ source "drivers/char/watchdog/Kconfig"
 
 comment "S/390 character device drivers"
 
+config HVC_DRIVER
+	bool
+	help
+	  Users of pSeries machines that want to utilize the hvc console front-end
+	  module for their backend console driver should select this option.
+	  It will automatically be selected if one of the back-end console drivers
+	  is selected.
+
+config HVC_IUCV
+	bool "Support for z/VM IUCV hypervisor console (VM only)"
+	depends on S390
+	select HVC_DRIVER
+	select IUCV
+	default y
+	help
+	  This driver provides a Hypervisor console (HVC) back-end to access
+	  a Linux (console) terminal using z/VM IUCV communication.
+
 config TN3270
 	tristate "Support for locally attached 3270 terminals"
 	help