kernel/virt_console-rollup2.patch

diff --git a/MAINTAINERS b/MAINTAINERS
index d371022..63c3620 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2336,12 +2336,6 @@ L:	linuxppc-dev@ozlabs.org
 S:	Odd Fixes
 F:	drivers/char/hvc_*
 
-VIRTIO CONSOLE DRIVER
-M:	Amit Shah <amit.shah@redhat.com>
-L:	virtualization@lists.linux-foundation.org
-S:	Maintained
-F:	drivers/char/virtio_console.c
-
 GSPCA FINEPIX SUBDRIVER
 M:	Frank Zago <frank@zago.net>
 L:	linux-media@vger.kernel.org
@@ -5682,6 +5676,13 @@ S:	Maintained
 F:	Documentation/filesystems/vfat.txt
 F:	fs/fat/
 
+VIRTIO CONSOLE DRIVER
+M:	Amit Shah <amit.shah@redhat.com>
+L:	virtualization@lists.linux-foundation.org
+S:	Maintained
+F:	drivers/char/virtio_console.c
+F:	include/linux/virtio_console.h
+
 VIRTIO HOST (VHOST)
 M:	"Michael S. Tsirkin" <mst@redhat.com>
 L:	kvm@vger.kernel.org
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 213373b..ab29b98 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -109,7 +109,6 @@ struct ports_device {
 	 * notification
 	 */
 	struct work_struct control_work;
-	struct work_struct config_work;
 
 	struct list_head ports;
 
@@ -159,6 +158,9 @@ struct port {
 	 */
 	spinlock_t inbuf_lock;
 
+	/* Protect the operations on the out_vq. */
+	spinlock_t outvq_lock;
+
 	/* The IO vqs for this port */
 	struct virtqueue *in_vq, *out_vq;
 
@@ -184,6 +186,8 @@ struct port {
 	/* The 'id' to identify the port with the Host */
 	u32 id;
 
+	bool outvq_full;
+
 	/* Is the host device open */
 	bool host_connected;
 
@@ -373,22 +377,22 @@ out:
 	return ret;
 }
 
-static ssize_t send_control_msg(struct port *port, unsigned int event,
-				unsigned int value)
+static ssize_t __send_control_msg(struct ports_device *portdev, u32 port_id,
+				  unsigned int event, unsigned int value)
 {
 	struct scatterlist sg[1];
 	struct virtio_console_control cpkt;
 	struct virtqueue *vq;
-	int len;
+	unsigned int len;
 
-	if (!use_multiport(port->portdev))
+	if (!use_multiport(portdev))
 		return 0;
 
-	cpkt.id = port->id;
+	cpkt.id = port_id;
 	cpkt.event = event;
 	cpkt.value = value;
 
-	vq = port->portdev->c_ovq;
+	vq = portdev->c_ovq;
 
 	sg_init_one(sg, &cpkt, sizeof(cpkt));
 	if (vq->vq_ops->add_buf(vq, sg, 1, 0, &cpkt) >= 0) {
@@ -399,15 +403,39 @@ static ssize_t send_control_msg(struct port *port, unsigned int event,
 	return 0;
 }
 
-static ssize_t send_buf(struct port *port, void *in_buf, size_t in_count)
+static ssize_t send_control_msg(struct port *port, unsigned int event,
+				unsigned int value)
+{
+	return __send_control_msg(port->portdev, port->id, event, value);
+}
+
+/* Callers must take the port->outvq_lock */
+static void reclaim_consumed_buffers(struct port *port)
+{
+	void *buf;
+	unsigned int len;
+
+	while ((buf = port->out_vq->vq_ops->get_buf(port->out_vq, &len))) {
+		kfree(buf);
+		port->outvq_full = false;
+	}
+}
+
+static ssize_t send_buf(struct port *port, void *in_buf, size_t in_count,
+			bool nonblock)
 {
 	struct scatterlist sg[1];
 	struct virtqueue *out_vq;
 	ssize_t ret;
+	unsigned long flags;
 	unsigned int len;
 
 	out_vq = port->out_vq;
 
+	spin_lock_irqsave(&port->outvq_lock, flags);
+
+	reclaim_consumed_buffers(port);
+
 	sg_init_one(sg, in_buf, in_count);
 	ret = out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, in_buf);
 
@@ -415,20 +443,31 @@ static ssize_t send_buf(struct port *port, void *in_buf, size_t in_count)
 	out_vq->vq_ops->kick(out_vq);
 
 	if (ret < 0) {
-		len = 0;
-		goto fail;
+		in_count = 0;
+		goto done;
 	}
 
+	if (ret == 0)
+		port->outvq_full = true;
+
+	if (nonblock)
+		goto done;
+
 	/*
 	 * Wait till the host acknowledges it pushed out the data we
-	 * sent. Also ensure we return to userspace the number of
-	 * bytes that were successfully consumed by the host.
+	 * sent.  This is done for ports in blocking mode or for data
+	 * from the hvc_console; the tty operations are performed with
+	 * spinlocks held so we can't sleep here.
 	 */
 	while (!out_vq->vq_ops->get_buf(out_vq, &len))
 		cpu_relax();
-fail:
-	/* We're expected to return the amount of data we wrote */
-	return len;
+done:
+	spin_unlock_irqrestore(&port->outvq_lock, flags);
+	/*
+	 * We're expected to return the amount of data we wrote -- all
+	 * of it
+	 */
+	return in_count;
 }
 
 /*
@@ -477,9 +516,28 @@ static ssize_t fill_readbuf(struct port *port, char *out_buf, size_t out_count,
 }
 
 /* The condition that must be true for polling to end */
-static bool wait_is_over(struct port *port)
+static bool will_read_block(struct port *port)
+{
+	return !port_has_data(port) && port->host_connected;
+}
+
+static bool will_write_block(struct port *port)
 {
-	return port_has_data(port) || !port->host_connected;
+	bool ret;
+
+	if (!port->host_connected)
+		return true;
+
+	spin_lock_irq(&port->outvq_lock);
+	/*
+	 * Check if the Host has consumed any buffers since we last
+	 * sent data (this is only applicable for nonblocking ports).
+	 */
+	reclaim_consumed_buffers(port);
+	ret = port->outvq_full;
+	spin_unlock_irq(&port->outvq_lock);
+
+	return ret;
 }
 
 static ssize_t port_fops_read(struct file *filp, char __user *ubuf,
@@ -502,7 +560,7 @@ static ssize_t port_fops_read(struct file *filp, char __user *ubuf,
 			return -EAGAIN;
 
 		ret = wait_event_interruptible(port->waitqueue,
-					       wait_is_over(port));
+					       !will_read_block(port));
 		if (ret < 0)
 			return ret;
 	}
@@ -528,9 +586,22 @@ static ssize_t port_fops_write(struct file *filp, const char __user *ubuf,
 	struct port *port;
 	char *buf;
 	ssize_t ret;
+	bool nonblock;
 
 	port = filp->private_data;
 
+	nonblock = filp->f_flags & O_NONBLOCK;
+
+	if (will_write_block(port)) {
+		if (nonblock)
+			return -EAGAIN;
+
+		ret = wait_event_interruptible(port->waitqueue,
+					       !will_write_block(port));
+		if (ret < 0)
+			return ret;
+	}
+
 	count = min((size_t)(32 * 1024), count);
 
 	buf = kmalloc(count, GFP_KERNEL);
@@ -543,9 +614,14 @@ static ssize_t port_fops_write(struct file *filp, const char __user *ubuf,
 		goto free_buf;
 	}
 
-	ret = send_buf(port, buf, count);
+	ret = send_buf(port, buf, count, nonblock);
+
+	if (nonblock && ret > 0)
+		goto out;
+
 free_buf:
 	kfree(buf);
+out:
 	return ret;
 }
 
@@ -560,7 +636,7 @@ static unsigned int port_fops_poll(struct file *filp, poll_table *wait)
 	ret = 0;
 	if (port->inbuf)
 		ret |= POLLIN | POLLRDNORM;
-	if (port->host_connected)
+	if (!will_write_block(port))
 		ret |= POLLOUT;
 	if (!port->host_connected)
 		ret |= POLLHUP;
@@ -584,6 +660,10 @@ static int port_fops_release(struct inode *inode, struct file *filp)
 
 	spin_unlock_irq(&port->inbuf_lock);
 
+	spin_lock_irq(&port->outvq_lock);
+	reclaim_consumed_buffers(port);
+	spin_unlock_irq(&port->outvq_lock);
+
 	return 0;
 }
 
@@ -612,6 +692,15 @@ static int port_fops_open(struct inode *inode, struct file *filp)
 	port->guest_connected = true;
 	spin_unlock_irq(&port->inbuf_lock);
 
+	spin_lock_irq(&port->outvq_lock);
+	/*
+	 * There might be a chance that we missed reclaiming a few
+	 * buffers in the window of the port getting previously closed
+	 * and opening now.
+	 */
+	reclaim_consumed_buffers(port);
+	spin_unlock_irq(&port->outvq_lock);
+
 	/* Notify host of port being opened */
 	send_control_msg(filp->private_data, VIRTIO_CONSOLE_PORT_OPEN, 1);
 
@@ -645,14 +734,14 @@ static int put_chars(u32 vtermno, const char *buf, int count)
 {
 	struct port *port;
 
-	port = find_port_by_vtermno(vtermno);
-	if (!port)
-		return 0;
-
 	if (unlikely(early_put_chars))
 		return early_put_chars(vtermno, buf, count);
 
-	return send_buf(port, (void *)buf, count);
+	port = find_port_by_vtermno(vtermno);
+	if (!port)
+		return -EPIPE;
+
+	return send_buf(port, (void *)buf, count, false);
 }
 
 /*
@@ -666,9 +755,13 @@ static int get_chars(u32 vtermno, char *buf, int count)
 {
 	struct port *port;
 
+	/* If we've not set up the port yet, we have no input to give. */
+	if (unlikely(early_put_chars))
+		return 0;
+
 	port = find_port_by_vtermno(vtermno);
 	if (!port)
-		return 0;
+		return -EPIPE;
 
 	/* If we don't have an input queue yet, we can't get input. */
 	BUG_ON(!port->in_vq);
@@ -681,6 +774,10 @@ static void resize_console(struct port *port)
 	struct virtio_device *vdev;
 	struct winsize ws;
 
+	/* The port could have been hot-unplugged */
+	if (!port)
+		return;
+
 	vdev = port->portdev->vdev;
 	if (virtio_has_feature(vdev, VIRTIO_CONSOLE_F_SIZE)) {
 		vdev->config->get(vdev,
@@ -774,6 +871,13 @@ int init_port_console(struct port *port)
 	spin_unlock_irq(&pdrvdata_lock);
 	port->guest_connected = true;
 
+	/*
+	 * Start using the new console output if this is the first
+	 * console to come up.
+	 */
+	if (early_put_chars)
+		early_put_chars = NULL;
+
 	/* Notify host of port being opened */
 	send_control_msg(port, VIRTIO_CONSOLE_PORT_OPEN, 1);
 
@@ -829,6 +933,8 @@ static ssize_t debugfs_read(struct file *filp, char __user *ubuf,
 	out_offset += snprintf(buf + out_offset, out_count - out_offset,
 			       "host_connected: %d\n", port->host_connected);
 	out_offset += snprintf(buf + out_offset, out_count - out_offset,
+			       "outvq_full: %d\n", port->outvq_full);
+	out_offset += snprintf(buf + out_offset, out_count - out_offset,
 			       "is_console: %s\n",
 			       is_console_port(port) ? "yes" : "no");
 	out_offset += snprintf(buf + out_offset, out_count - out_offset,
@@ -845,6 +951,140 @@ static const struct file_operations port_debugfs_ops = {
 	.read  = debugfs_read,
 };
 
+static unsigned int fill_queue(struct virtqueue *vq, spinlock_t *lock)
+{
+	struct port_buffer *buf;
+	unsigned int nr_added_bufs;
+	int ret;
+
+	nr_added_bufs = 0;
+	do {
+		buf = alloc_buf(PAGE_SIZE);
+		if (!buf)
+			break;
+
+		spin_lock_irq(lock);
+		ret = add_inbuf(vq, buf);
+		if (ret < 0) {
+			spin_unlock_irq(lock);
+			free_buf(buf);
+			break;
+		}
+		nr_added_bufs++;
+		spin_unlock_irq(lock);
+	} while (ret > 0);
+
+	return nr_added_bufs;
+}
+
+static int add_port(struct ports_device *portdev, u32 id)
+{
+	char debugfs_name[16];
+	struct port *port;
+	struct port_buffer *buf;
+	dev_t devt;
+	unsigned int nr_added_bufs;
+	int err;
+
+	port = kmalloc(sizeof(*port), GFP_KERNEL);
+	if (!port) {
+		err = -ENOMEM;
+		goto fail;
+	}
+
+	port->portdev = portdev;
+	port->id = id;
+
+	port->name = NULL;
+	port->inbuf = NULL;
+	port->cons.hvc = NULL;
+
+	port->host_connected = port->guest_connected = false;
+
+	port->outvq_full = false;
+
+	port->in_vq = portdev->in_vqs[port->id];
+	port->out_vq = portdev->out_vqs[port->id];
+
+	cdev_init(&port->cdev, &port_fops);
+
+	devt = MKDEV(portdev->chr_major, id);
+	err = cdev_add(&port->cdev, devt, 1);
+	if (err < 0) {
+		dev_err(&port->portdev->vdev->dev,
+			"Error %d adding cdev for port %u\n", err, id);
+		goto free_port;
+	}
+	port->dev = device_create(pdrvdata.class, &port->portdev->vdev->dev,
+				  devt, port, "vport%up%u",
+				  port->portdev->drv_index, id);
+	if (IS_ERR(port->dev)) {
+		err = PTR_ERR(port->dev);
+		dev_err(&port->portdev->vdev->dev,
+			"Error %d creating device for port %u\n",
+			err, id);
+		goto free_cdev;
+	}
+
+	spin_lock_init(&port->inbuf_lock);
+	spin_lock_init(&port->outvq_lock);
+	init_waitqueue_head(&port->waitqueue);
+
+	/* Fill the in_vq with buffers so the host can send us data. */
+	nr_added_bufs = fill_queue(port->in_vq, &port->inbuf_lock);
+	if (!nr_added_bufs) {
+		dev_err(port->dev, "Error allocating inbufs\n");
+		err = -ENOMEM;
+		goto free_device;
+	}
+
+	/*
+	 * If we're not using multiport support, this has to be a console port
+	 */
+	if (!use_multiport(port->portdev)) {
+		err = init_port_console(port);
+		if (err)
+			goto free_inbufs;
+	}
+
+	spin_lock_irq(&portdev->ports_lock);
+	list_add_tail(&port->list, &port->portdev->ports);
+	spin_unlock_irq(&portdev->ports_lock);
+
+	/*
+	 * Tell the Host we're set so that it can send us various
+	 * configuration parameters for this port (eg, port name,
+	 * caching, whether this is a console port, etc.)
+	 */
+	send_control_msg(port, VIRTIO_CONSOLE_PORT_READY, 1);
+
+	if (pdrvdata.debugfs_dir) {
+		/*
+		 * Finally, create the debugfs file that we can use to
+		 * inspect a port's state at any time
+		 */
+		sprintf(debugfs_name, "vport%up%u",
+			port->portdev->drv_index, id);
+		port->debugfs_file = debugfs_create_file(debugfs_name, 0444,
+							 pdrvdata.debugfs_dir,
+							 port,
+							 &port_debugfs_ops);
+	}
+	return 0;
+
+free_inbufs:
+	while ((buf = port->in_vq->vq_ops->detach_unused_buf(port->in_vq)))
+		free_buf(buf);
+free_device:
+	device_destroy(pdrvdata.class, port->dev->devt);
+free_cdev:
+	cdev_del(&port->cdev);
+free_port:
+	kfree(port);
+fail:
+	return err;
+}
+
 /* Remove all port-specific data. */
 static int remove_port(struct port *port)
 {
@@ -858,7 +1098,18 @@ static int remove_port(struct port *port)
 		spin_lock_irq(&pdrvdata_lock);
 		list_del(&port->cons.list);
 		spin_unlock_irq(&pdrvdata_lock);
+#if 0
+		/*
+		 * hvc_remove() not called as removing one hvc port
+		 * results in other hvc ports getting frozen.
+		 *
+		 * Once this is resolved in hvc, this functionality
+		 * will be enabled.  Till that is done, the -EPIPE
+		 * return from get_chars() above will help
+		 * hvc_console.c to clean up on ports we remove here.
+		 */
 		hvc_remove(port->cons.hvc);
+#endif
 	}
 	if (port->guest_connected)
 		send_control_msg(port, VIRTIO_CONSOLE_PORT_OPEN, 0);
@@ -870,6 +1121,8 @@ static int remove_port(struct port *port)
 	/* Remove unused data this port might have received. */
 	discard_port_data(port);
 
+	reclaim_consumed_buffers(port);
+
 	/* Remove buffers we queued up for the Host to send us data in. */
 	while ((buf = port->in_vq->vq_ops->detach_unused_buf(port->in_vq)))
 		free_buf(buf);
@@ -894,7 +1147,7 @@ static void handle_control_message(struct ports_device *portdev,
 	cpkt = (struct virtio_console_control *)(buf->buf + buf->offset);
 
 	port = find_port_by_id(portdev, cpkt->id);
-	if (!port) {
+	if (!port && cpkt->event != VIRTIO_CONSOLE_PORT_ADD) {
 		/* No valid header at start of buffer.  Drop it. */
 		dev_dbg(&portdev->vdev->dev,
 			"Invalid index %u in control packet\n", cpkt->id);
@@ -902,6 +1155,24 @@ static void handle_control_message(struct ports_device *portdev,
 	}
 
 	switch (cpkt->event) {
+	case VIRTIO_CONSOLE_PORT_ADD:
+		if (port) {
+			dev_dbg(&portdev->vdev->dev,
+				"Port %u already added\n", port->id);
+			send_control_msg(port, VIRTIO_CONSOLE_PORT_READY, 1);
+			break;
+		}
+		if (cpkt->id >= portdev->config.max_nr_ports) {
+			dev_warn(&portdev->vdev->dev,
+				"Request for adding port with out-of-bound id %u, max. supported id: %u\n",
+				cpkt->id, portdev->config.max_nr_ports - 1);
+			break;
+		}
+		add_port(portdev, cpkt->id);
+		break;
+	case VIRTIO_CONSOLE_PORT_REMOVE:
+		remove_port(port);
+		break;
 	case VIRTIO_CONSOLE_CONSOLE_PORT:
 		if (!cpkt->value)
 			break;
@@ -923,6 +1194,14 @@ static void handle_control_message(struct ports_device *portdev,
 	case VIRTIO_CONSOLE_PORT_OPEN:
 		port->host_connected = cpkt->value;
 		wake_up_interruptible(&port->waitqueue);
+		/*
+		 * If the host port got closed and the host had any
+		 * unconsumed buffers, we'll be able to reclaim them
+		 * now.
+		 */
+		spin_lock_irq(&port->outvq_lock);
+		reclaim_consumed_buffers(port);
+		spin_unlock_irq(&port->outvq_lock);
 		break;
 	case VIRTIO_CONSOLE_PORT_NAME:
 		/*
@@ -947,37 +1226,18 @@ static void handle_control_message(struct ports_device *portdev,
 		 */
 		err = sysfs_create_group(&port->dev->kobj,
 					 &port_attribute_group);
-		if (err)
+		if (err) {
 			dev_err(port->dev,
 				"Error %d creating sysfs device attributes\n",
 				err);
-
-		break;
-	case VIRTIO_CONSOLE_PORT_REMOVE:
-		/*
-		 * Hot unplug the port.  We don't decrement nr_ports
-		 * since we don't want to deal with extra complexities
-		 * of using the lowest-available port id: We can just
-		 * pick up the nr_ports number as the id and not have
-		 * userspace send it to us.  This helps us in two
-		 * ways:
-		 *
-		 * - We don't need to have a 'port_id' field in the
-		 *   config space when a port is hot-added.  This is a
-		 *   good thing as we might queue up multiple hotplug
-		 *   requests issued in our workqueue.
-		 *
-		 * - Another way to deal with this would have been to
-		 *   use a bitmap of the active ports and select the
-		 *   lowest non-active port from that map.  That
-		 *   bloats the already tight config space and we
-		 *   would end up artificially limiting the
-		 *   max. number of ports to sizeof(bitmap).  Right
-		 *   now we can support 2^32 ports (as the port id is
-		 *   stored in a u32 type).
-		 *
-		 */
-		remove_port(port);
+		} else {
+			/*
+			 * Generate a udev event so that appropriate
+			 * symlinks can be created based on udev
+			 * rules.
+			 */
+			kobject_uevent(&port->dev->kobj, KOBJ_CHANGE);
+		}
 		break;
 	}
 }
@@ -1055,10 +1315,7 @@ static void config_intr(struct virtio_device *vdev)
 	struct ports_device *portdev;
 
 	portdev = vdev->priv;
-	if (use_multiport(portdev)) {
-		/* Handle port hot-add */
-		schedule_work(&portdev->config_work);
-	}
+
 	/*
 	 * We'll use this way of resizing only for legacy support.
 	 * For newer userspace (VIRTIO_CONSOLE_F_MULTPORT+), use
@@ -1068,192 +1325,6 @@ static void config_intr(struct virtio_device *vdev)
 	resize_console(find_port_by_id(portdev, 0));
 }
 
-static unsigned int fill_queue(struct virtqueue *vq, spinlock_t *lock)
-{
-	struct port_buffer *buf;
-	unsigned int ret;
-	int err;
-
-	ret = 0;
-	do {
-		buf = alloc_buf(PAGE_SIZE);
-		if (!buf)
-			break;
-
-		spin_lock_irq(lock);
-		err = add_inbuf(vq, buf);
-		if (err < 0) {
-			spin_unlock_irq(lock);
-			free_buf(buf);
-			break;
-		}
-		ret++;
-		spin_unlock_irq(lock);
-	} while (err > 0);
-
-	return ret;
-}
-
-static int add_port(struct ports_device *portdev, u32 id)
-{
-	char debugfs_name[16];
-	struct port *port;
-	struct port_buffer *buf;
-	dev_t devt;
-	int err;
-
-	port = kmalloc(sizeof(*port), GFP_KERNEL);
-	if (!port) {
-		err = -ENOMEM;
-		goto fail;
-	}
-
-	port->portdev = portdev;
-	port->id = id;
-
-	port->name = NULL;
-	port->inbuf = NULL;
-	port->cons.hvc = NULL;
-
-	port->host_connected = port->guest_connected = false;
-
-	port->in_vq = portdev->in_vqs[port->id];
-	port->out_vq = portdev->out_vqs[port->id];
-
-	cdev_init(&port->cdev, &port_fops);
-
-	devt = MKDEV(portdev->chr_major, id);
-	err = cdev_add(&port->cdev, devt, 1);
-	if (err < 0) {
-		dev_err(&port->portdev->vdev->dev,
-			"Error %d adding cdev for port %u\n", err, id);
-		goto free_port;
-	}
-	port->dev = device_create(pdrvdata.class, &port->portdev->vdev->dev,
-				  devt, port, "vport%up%u",
-				  port->portdev->drv_index, id);
-	if (IS_ERR(port->dev)) {
-		err = PTR_ERR(port->dev);
-		dev_err(&port->portdev->vdev->dev,
-			"Error %d creating device for port %u\n",
-			err, id);
-		goto free_cdev;
-	}
-
-	spin_lock_init(&port->inbuf_lock);
-	init_waitqueue_head(&port->waitqueue);
-
-	/* Fill the in_vq with buffers so the host can send us data. */
-	err = fill_queue(port->in_vq, &port->inbuf_lock);
-	if (!err) {
-		dev_err(port->dev, "Error allocating inbufs\n");
-		err = -ENOMEM;
-		goto free_device;
-	}
-
-	/*
-	 * If we're not using multiport support, this has to be a console port
-	 */
-	if (!use_multiport(port->portdev)) {
-		err = init_port_console(port);
-		if (err)
-			goto free_inbufs;
-	}
-
-	spin_lock_irq(&portdev->ports_lock);
-	list_add_tail(&port->list, &port->portdev->ports);
-	spin_unlock_irq(&portdev->ports_lock);
-
-	/*
-	 * Tell the Host we're set so that it can send us various
-	 * configuration parameters for this port (eg, port name,
-	 * caching, whether this is a console port, etc.)
-	 */
-	send_control_msg(port, VIRTIO_CONSOLE_PORT_READY, 1);
-
-	if (pdrvdata.debugfs_dir) {
-		/*
-		 * Finally, create the debugfs file that we can use to
-		 * inspect a port's state at any time
-		 */
-		sprintf(debugfs_name, "vport%up%u",
-			port->portdev->drv_index, id);
-		port->debugfs_file = debugfs_create_file(debugfs_name, 0444,
-							 pdrvdata.debugfs_dir,
-							 port,
-							 &port_debugfs_ops);
-	}
-	return 0;
-
-free_inbufs:
-	while ((buf = port->in_vq->vq_ops->detach_unused_buf(port->in_vq)))
-		free_buf(buf);
-free_device:
-	device_destroy(pdrvdata.class, port->dev->devt);
-free_cdev:
-	cdev_del(&port->cdev);
-free_port:
-	kfree(port);
-fail:
-	return err;
-}
-
-/*
- * The workhandler for config-space updates.
- *
- * This is called when ports are hot-added.
- */
-static void config_work_handler(struct work_struct *work)
-{
-	struct virtio_console_config virtconconf;
-	struct ports_device *portdev;
-	struct virtio_device *vdev;
-	int err;
-
-	portdev = container_of(work, struct ports_device, config_work);
-
-	vdev = portdev->vdev;
-	vdev->config->get(vdev,
-			  offsetof(struct virtio_console_config, nr_ports),
-			  &virtconconf.nr_ports,
-			  sizeof(virtconconf.nr_ports));
-
-	if (portdev->config.nr_ports == virtconconf.nr_ports) {
-		/*
-		 * Port 0 got hot-added.  Since we already did all the
-		 * other initialisation for it, just tell the Host
-		 * that the port is ready if we find the port.  In
-		 * case the port was hot-removed earlier, we call
-		 * add_port to add the port.
-		 */
-		struct port *port;
-
-		port = find_port_by_id(portdev, 0);
-		if (!port)
-			add_port(portdev, 0);
-		else
-			send_control_msg(port, VIRTIO_CONSOLE_PORT_READY, 1);
-		return;
-	}
-	if (virtconconf.nr_ports > portdev->config.max_nr_ports) {
-		dev_warn(&vdev->dev,
-			 "More ports specified (%u) than allowed (%u)",
-			 portdev->config.nr_ports + 1,
-			 portdev->config.max_nr_ports);
-		return;
-	}
-	if (virtconconf.nr_ports < portdev->config.nr_ports)
-		return;
-
-	/* Hot-add ports */
-	while (virtconconf.nr_ports - portdev->config.nr_ports) {
-		err = add_port(portdev, portdev->config.nr_ports);
-		if (err)
-			break;
-		portdev->config.nr_ports++;
-	}
-}
-
 static int init_vqs(struct ports_device *portdev)
 {
 	vq_callback_t **io_callbacks;
@@ -1375,7 +1446,6 @@ static const struct file_operations portdev_fops = {
 static int __devinit virtcons_probe(struct virtio_device *vdev)
 {
 	struct ports_device *portdev;
-	u32 i;
 	int err;
 	bool multiport;
 
@@ -1404,29 +1474,15 @@ static int __devinit virtcons_probe(struct virtio_device *vdev)
 	}
 
 	multiport = false;
-	portdev->config.nr_ports = 1;
 	portdev->config.max_nr_ports = 1;
 	if (virtio_has_feature(vdev, VIRTIO_CONSOLE_F_MULTIPORT)) {
 		multiport = true;
 		vdev->features[0] |= 1 << VIRTIO_CONSOLE_F_MULTIPORT;
 
 		vdev->config->get(vdev, offsetof(struct virtio_console_config,
-						 nr_ports),
-				  &portdev->config.nr_ports,
-				  sizeof(portdev->config.nr_ports));
-		vdev->config->get(vdev, offsetof(struct virtio_console_config,
 						 max_nr_ports),
 				  &portdev->config.max_nr_ports,
 				  sizeof(portdev->config.max_nr_ports));
-		if (portdev->config.nr_ports > portdev->config.max_nr_ports) {
-			dev_warn(&vdev->dev,
-				 "More ports (%u) specified than allowed (%u). Will init %u ports.",
-				 portdev->config.nr_ports,
-				 portdev->config.max_nr_ports,
-				 portdev->config.max_nr_ports);
-
-			portdev->config.nr_ports = portdev->config.max_nr_ports;
-		}
 	}
 
 	/* Let the Host know we support multiple ports.*/
@@ -1442,24 +1498,28 @@ static int __devinit virtcons_probe(struct virtio_device *vdev)
 	INIT_LIST_HEAD(&portdev->ports);
 
 	if (multiport) {
+		unsigned int nr_added_bufs;
+
 		spin_lock_init(&portdev->cvq_lock);
 		INIT_WORK(&portdev->control_work, &control_work_handler);
-		INIT_WORK(&portdev->config_work, &config_work_handler);
 
-		err = fill_queue(portdev->c_ivq, &portdev->cvq_lock);
-		if (!err) {
+		nr_added_bufs = fill_queue(portdev->c_ivq, &portdev->cvq_lock);
+		if (!nr_added_bufs) {
 			dev_err(&vdev->dev,
 				"Error allocating buffers for control queue\n");
 			err = -ENOMEM;
 			goto free_vqs;
 		}
+	} else {
+		/*
+		 * For backward compatibility: Create a console port
+		 * if we're running on older host.
+		 */
+		add_port(portdev, 0);
 	}
 
-	for (i = 0; i < portdev->config.nr_ports; i++)
-		add_port(portdev, i);
-
-	/* Start using the new console output. */
-	early_put_chars = NULL;
+	__send_control_msg(portdev, VIRTIO_CONSOLE_BAD_ID,
+			   VIRTIO_CONSOLE_DEVICE_READY, 1);
 	return 0;
 
 free_vqs:
@@ -1471,6 +1531,9 @@ free_chrdev:
 free:
 	kfree(portdev);
 fail:
+	/* The host might want to notify mgmt sw about device add failure */
+	__send_control_msg(portdev, VIRTIO_CONSOLE_BAD_ID,
+			   VIRTIO_CONSOLE_DEVICE_READY, 0);
 	return err;
 }
 
@@ -1484,7 +1547,6 @@ static void virtcons_remove(struct virtio_device *vdev)
 	portdev = vdev->priv;
 
 	cancel_work_sync(&portdev->control_work);
-	cancel_work_sync(&portdev->config_work);
 
 	list_for_each_entry_safe(port, port2, &portdev->ports, list)
 		remove_port(port);
diff --git a/include/linux/virtio_console.h b/include/linux/virtio_console.h
index ae4f039..a85064d 100644
--- a/include/linux/virtio_console.h
+++ b/include/linux/virtio_console.h
@@ -14,6 +14,8 @@
 #define VIRTIO_CONSOLE_F_SIZE	0	/* Does host provide console size? */
 #define VIRTIO_CONSOLE_F_MULTIPORT 1	/* Does host provide multiple ports? */
 
+#define VIRTIO_CONSOLE_BAD_ID		(~(u32)0)
+
 struct virtio_console_config {
 	/* colums of the screens */
 	__u16 cols;
@@ -21,8 +23,6 @@ struct virtio_console_config {
 	__u16 rows;
 	/* max. number of ports this device can hold */
 	__u32 max_nr_ports;
-	/* number of ports added so far */
-	__u32 nr_ports;
 } __attribute__((packed));
 
 /*
@@ -36,12 +36,14 @@ struct virtio_console_control {
 };
 
 /* Some events for control messages */
-#define VIRTIO_CONSOLE_PORT_READY	0
-#define VIRTIO_CONSOLE_CONSOLE_PORT	1
-#define VIRTIO_CONSOLE_RESIZE		2
-#define VIRTIO_CONSOLE_PORT_OPEN	3
-#define VIRTIO_CONSOLE_PORT_NAME	4
-#define VIRTIO_CONSOLE_PORT_REMOVE	5
+#define VIRTIO_CONSOLE_DEVICE_READY	0
+#define VIRTIO_CONSOLE_PORT_ADD		1
+#define VIRTIO_CONSOLE_PORT_REMOVE	2
+#define VIRTIO_CONSOLE_PORT_READY	3
+#define VIRTIO_CONSOLE_CONSOLE_PORT	4
+#define VIRTIO_CONSOLE_RESIZE		5
+#define VIRTIO_CONSOLE_PORT_OPEN	6
+#define VIRTIO_CONSOLE_PORT_NAME	7
 
 #ifdef __KERNEL__
 int __init virtio_cons_early_init(int (*put_chars)(u32, const char *, int));