[Qemu-devel] virtio-serial: A guest <-> host interface for simple communication

[Qemu-devel] virtio-serial: A guest <-> host interface for simple communication

[Amit Shah]

Hello,

Here are two patches. One implements a virtio-serial device in qemu
and the other is the driver for a guest kernel.

While working on a vmchannel interface that is needed for communication
between guest userspace and host userspace, I saw that most of the
interface can be abstracted out as a "serial" device with "ports".

Some requirements for a vmchannel are listed at this page:
http://kvm.et.redhat.com/page/VMchannel_Requirements

A few sample uses for a vmchannel are to share the host and guest
clipboards (to allow copy/paste between a host and a guest), to
lock the screen of the guest session when the vnc viewer is closed,
to find out which applications are installed on a guest OS even when
the guest is powered down (using virt-inspector) and so on.

At this time, the qemu device is more complete than the guest driver
is. However, I'd like you to review both the patches for inclusion.

Thanks,
		Amit.

[Qemu-devel] [PATCH] virtio_serial: A char device for simple guest <-> host communication

[Amit Shah]

We expose multiple char devices ("ports") for simple communication
between the host userspace and guest.

This is mainly intended for obtaining information from the guest.
Sample offline usages can be: poking around in a guest to find out
the file systems used, applications installed, etc. Online usages
can be sharing of clipboard data between the guest and the host,
sending information about logged-in users to the host, locking the
screen or session when a vnc session is closed, and so on.

The interface presented to guest userspace is of a simple char
device, so it can be used like this:

	fd = open("/dev/vmch0", O_RDWR);
	ret = read(fd, buf, 100);
        ret = write(fd, string, strlen(string));
	ret = ioctl(fd, VIRTIO_SERIAL_IOCTL_GET_PORT_NAME, &port_name);

Signed-off-by: Amit Shah <amit.shah@redhat.com>
---
 drivers/char/Kconfig          |    6 +
 drivers/char/Makefile         |    1 +
 drivers/char/virtio_serial.c  |  571 +++++++++++++++++++++++++++++++++++++++++
 include/linux/virtio_serial.h |   42 +++
 4 files changed, 620 insertions(+), 0 deletions(-)
 create mode 100644 drivers/char/virtio_serial.c
 create mode 100644 include/linux/virtio_serial.h

diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index 30bae6d..84a1718 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -679,6 +679,12 @@ config VIRTIO_CONSOLE
 	help
 	  Virtio console for use with lguest and other hypervisors.
 
+config VIRTIO_SERIAL
+	tristate "Virtio serial"
+	select VIRTIO
+	select VIRTIO_RING
+	help
+	  Virtio serial device driver for simple guest and host communication
 
 config HVCS
 	tristate "IBM Hypervisor Virtual Console Server support"
diff --git a/drivers/char/Makefile b/drivers/char/Makefile
index 189efcf..0b6c71e 100644
--- a/drivers/char/Makefile
+++ b/drivers/char/Makefile
@@ -54,6 +54,7 @@ obj-$(CONFIG_HVC_XEN)		+= hvc_xen.o
 obj-$(CONFIG_HVC_IUCV)		+= hvc_iucv.o
 obj-$(CONFIG_HVC_UDBG)		+= hvc_udbg.o
 obj-$(CONFIG_VIRTIO_CONSOLE)	+= virtio_console.o
+obj-$(CONFIG_VIRTIO_SERIAL)	+= virtio_serial.o
 obj-$(CONFIG_RAW_DRIVER)	+= raw.o
 obj-$(CONFIG_SGI_SNSC)		+= snsc.o snsc_event.o
 obj-$(CONFIG_MSPEC)		+= mspec.o
diff --git a/drivers/char/virtio_serial.c b/drivers/char/virtio_serial.c
new file mode 100644
index 0000000..6c5ad5d
--- /dev/null
+++ b/drivers/char/virtio_serial.c
@@ -0,0 +1,571 @@
+/*
+ * VirtIO Serial driver
+ *
+ * This is paravirtualised serial guest<->host communication channel
+ * for relaying short messages and events in either direction.
+ *
+ * One PCI device can have multiple serial ports so that different
+ * applications can communicate without polluting the PCI device space
+ * in the guest.
+ *
+ * Copyright (C) 2009, Red Hat, Inc.
+ *
+ * Author(s): Amit Shah <amit.shah@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#include <linux/cdev.h>
+#include <linux/err.h>
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/poll.h>
+#include <linux/virtio.h>
+#include <linux/virtio_serial.h>
+#include <linux/workqueue.h>
+
+struct virtio_serial_struct {
+	struct virtio_device *vdev;
+	struct virtqueue *ctrl_vq;
+	struct virtqueue *in_vq, *out_vq;
+	struct virtio_serial_port *ports;
+	u32 nr_ports;
+	struct work_struct rx_work;
+	struct work_struct queue_work;
+};
+
+struct virtio_serial_port_buffer {
+	unsigned int len;
+	unsigned int offset;
+	char *buf;
+
+	struct list_head list;
+};
+
+struct virtio_serial_id {
+	u32 id; /* Port number */
+};
+
+struct virtio_serial_port {
+	struct virtio_serial_struct *virtserial;
+
+	/* The name given to this channel, if any. NOT zero-terminated */
+	char *name;
+
+	/* Each port associates with a separate char device */
+	dev_t dev;
+	struct cdev cdev;
+
+	/* Buffer management */
+	struct virtio_serial_port_buffer read_buf;
+	struct list_head readbuf_head;
+};
+
+static struct virtio_serial_struct virtserial;
+
+/* This should become per-port data */
+static DECLARE_COMPLETION(have_data);
+
+static int major = 60; /* from the experimental range */
+
+static struct virtio_serial_port *get_port_from_id(u32 id)
+{
+	if (id > virtserial.nr_ports)
+		return NULL;
+
+	return &virtserial.ports[id];
+}
+
+static int get_id_from_port(struct virtio_serial_port *port)
+{
+	u32 i;
+
+	for (i = 0; i < virtserial.nr_ports; i++) {
+		if (port == &virtserial.ports[i])
+			return i;
+	}
+	return VIRTIO_SERIAL_BAD_ID;
+}
+
+static struct virtio_serial_port *get_port_from_buf(char *buf)
+{
+	u32 id;
+
+	memcpy(&id, buf, sizeof(id));
+	if (id > virtserial.nr_ports)
+		return NULL;
+
+	return &virtserial.ports[id];
+}
+
+static void virtio_serial_queue_work_handler(struct work_struct *work)
+{
+	struct scatterlist sg[1];
+	struct page *page;
+	struct virtqueue *vq;
+	int ret;
+
+	vq = virtserial.in_vq;
+	while (1) {
+		page = kzalloc(PAGE_SIZE, GFP_KERNEL);
+		if (!page)
+			break;
+
+		sg_init_one(sg, page, PAGE_SIZE);
+
+		ret = vq->vq_ops->add_buf(vq, sg, 0, 1, page);
+		if (ret < 0) {
+			kfree(page);
+			break;
+		}
+	}
+	vq->vq_ops->kick(vq);
+}
+
+static void virtio_serial_rx_work_handler(struct work_struct *work)
+{
+	struct virtio_serial_port *port = NULL;
+	struct virtio_serial_port_buffer *buf;
+	struct virtqueue *vq;
+	char *tmpbuf;
+	unsigned int tmplen;
+
+	vq = virtserial.in_vq;
+	while ((tmpbuf = vq->vq_ops->get_buf(vq, &tmplen))) {
+		port = get_port_from_buf(tmpbuf);
+		if (!port) {
+			/* No valid index at start of
+			 * buffer. Drop it.
+			 */
+			pr_debug("%s: invalid index in buffer, %c %d\n",
+				 __func__, tmpbuf[0], tmpbuf[0]);
+			break;
+		}
+		buf = kzalloc(sizeof(struct virtio_serial_port_buffer),
+			      GFP_KERNEL);
+		if (!buf)
+			break;
+
+		buf->buf = tmpbuf;
+		buf->len = tmplen;
+		buf->offset = sizeof(struct virtio_serial_id);
+		list_add_tail(&buf->list, &port->readbuf_head);
+
+		complete(&have_data);
+	}
+	/* Allocate buffers for all the ones that got used up */
+	schedule_work(&virtserial.queue_work);
+}
+
+static void receive_data(struct virtqueue *vq)
+{
+	schedule_work(&virtserial.rx_work);
+}
+
+static int receive_control_response(struct virtqueue *vq)
+{
+	int ret;
+	char *data;
+	unsigned int len;
+	struct virtio_serial_port *port;
+	struct virtio_serial_control ser_control;
+
+	/* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
+	data = vq->vq_ops->get_buf(vq, &len);
+	if (!data)
+		return 0;
+
+	/* Not enough data for the ioctl:
+	 * key + id + data
+	 */
+	/* XXX: return something else? */
+	if (len < sizeof(ser_control) + 1)
+		return -EIO;
+
+	memcpy(&ser_control, data, sizeof(ser_control));
+	len -= sizeof(ser_control);
+
+	ret = -EINVAL;
+	switch (ser_control.key) {
+	case VIRTIO_SERIAL_GET_PORT_NAME:
+		port = get_port_from_id(ser_control.port_nr);
+		if (!port) {
+			ret = -EINVAL;
+			break;
+		}
+
+		if (len > VIRTIO_SERIAL_NAME_MAX_LEN)
+			len = VIRTIO_SERIAL_NAME_MAX_LEN;
+
+		/* If the port is getting renamed */
+		kfree(port->name);
+
+		port->name = kzalloc(len, GFP_KERNEL);
+		if (!port->name) {
+			ret = -ENOMEM;
+			break;
+		}
+		memcpy(port->name, data + sizeof(ser_control), len);
+		ret = len;
+		break;
+	}
+	return ret;
+}
+
+static int request_control_info(struct virtio_serial_control *ser_control)
+{
+	int ret;
+	char *vbuf, *obuf;
+	struct scatterlist sg[2];
+
+	vbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!vbuf)
+		return -ENOMEM;
+	obuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!obuf)
+		return -ENOMEM;
+
+	memcpy(vbuf, ser_control, sizeof(ser_control));
+
+	sg_init_table(sg, 2);
+	sg_set_buf(&sg[0], vbuf, PAGE_SIZE);
+	sg_set_buf(&sg[1], obuf, PAGE_SIZE);
+
+	if (virtserial.ctrl_vq->vq_ops->add_buf(virtserial.ctrl_vq, sg, 1, 1,
+						obuf) == 0) {
+		/* Tell Host to go! */
+		virtserial.ctrl_vq->vq_ops->kick(virtserial.ctrl_vq);
+
+		/* Chill out until it's done with the buffer. */
+		while (!(ret = receive_control_response(virtserial.ctrl_vq)))
+			cpu_relax();
+	}
+	kfree(vbuf);
+	kfree(obuf);
+
+	return ret;
+}
+
+static ssize_t virtserial_read(struct file *filp, char __user *ubuf,
+			       size_t count, loff_t *offp)
+{
+	struct list_head *ptr, *ptr2;
+	struct virtio_serial_port *port;
+	struct virtio_serial_port_buffer *buf;
+	ssize_t ret;
+
+	port = filp->private_data;
+
+	if (list_empty(&port->readbuf_head))
+		return 0;
+
+	list_for_each_safe(ptr, ptr2, &port->readbuf_head) {
+		buf = list_entry(ptr, struct virtio_serial_port_buffer, list);
+
+		/* FIXME: other buffers further in this list might
+		 * have data too
+		 */
+		if (count > buf->len - buf->offset)
+			count = buf->len - buf->offset;
+
+		ret = copy_to_user(ubuf, buf->buf + buf->offset, count);
+
+		/* Return the number of bytes actually copied */
+		ret = count - ret;
+
+		buf->offset += ret;
+
+		if (buf->len - buf->offset == 0) {
+			list_del(&buf->list);
+			kfree(buf->buf);
+			kfree(buf);
+		}
+		/* FIXME: if there's more data requested and more data
+		 * available, return it.
+		 */
+		break;
+	}
+
+	return ret;
+}
+
+static ssize_t virtserial_write(struct file *filp, const char __user *ubuf,
+				size_t count, loff_t *offp)
+{
+	ssize_t ret;
+	char *vbuf;
+	unsigned int len, size;
+	struct virtqueue *out_vq;
+	struct scatterlist sg[1];
+	struct virtio_serial_port *port;
+	struct virtio_serial_id id;
+
+	port = filp->private_data;
+
+	id.id = get_id_from_port(port);
+
+	size = min(count + sizeof(id), PAGE_SIZE);
+	vbuf = kmalloc(size, GFP_KERNEL);
+	if (!vbuf)
+		return -EFBIG;
+
+	memcpy(vbuf, &id, sizeof(id));
+	size -= sizeof(id);
+
+	ret = copy_from_user(vbuf + sizeof(id), ubuf, size);
+
+	/* Return the number of bytes actually written */
+	ret = size - ret;
+
+	out_vq = virtserial.out_vq;
+
+	sg_init_one(sg, vbuf, ret + sizeof(id));
+
+	/* add_buf wants a token to identify this buffer: we hand it any
+	 * non-NULL pointer, since there's only ever one buffer.
+	 */
+	if (out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, (void *)1) == 0) {
+		/* Tell Host to go! */
+		out_vq->vq_ops->kick(out_vq);
+		/* Chill out until it's done with the buffer. */
+		while (!out_vq->vq_ops->get_buf(out_vq, &len))
+			cpu_relax();
+	}
+	kfree(vbuf);
+
+	/* FIXME: Write out the complete data in more buffers,
+	 * don't just bail out after one
+	 */
+
+	/* We're expected to return the amount of data we wrote */
+	return ret;
+}
+
+static long virtserial_ioctl(struct file *filp, unsigned int ioctl,
+			     unsigned long arg)
+{
+	long ret;
+	struct virtio_serial_control ser_control;
+	struct virtio_serial_port *port;
+	struct virtio_serial_port_name *port_name;
+
+	port = filp->private_data;
+	ser_control.port_nr = get_id_from_port(port);
+
+	ret = -EINVAL;
+	switch (ioctl) {
+	case VIRTIO_SERIAL_IOCTL_GET_PORT_NAME:
+
+		port_name = (struct virtio_serial_port_name *)arg;
+
+		if (!port->name) {
+			if (ser_control.port_nr == VIRTIO_SERIAL_BAD_ID) {
+				ret = -EINVAL;
+				break;
+			}
+			ser_control.key = VIRTIO_SERIAL_GET_PORT_NAME;
+			ret = request_control_info(&ser_control);
+			if (ret < 0) {
+				/* Of IOCTL error return codes, only
+				 * this one comes close to what has
+				 * happened: either out of memory or
+				 * the virtio-serial backend didn't
+				 * have the associated name for the
+				 * port
+				 */
+				ret = -EINVAL;
+				break;
+			}
+		}
+		ret = copy_to_user(port_name->name,
+				   port->name, VIRTIO_SERIAL_NAME_MAX_LEN);
+		if (ret < 0) {
+			ret = -EINVAL;
+			break;
+		}
+		if (ret > 0) {
+			/* Do something? There still is data to be
+			 * copied to userspace
+			 */
+			ret = 0;
+		}
+		break;
+	}
+	return ret;
+}
+
+static int virtserial_release(struct inode *inode, struct file *filp)
+{
+	pr_notice("%s\n", __func__);
+	return 0;
+}
+
+static int virtserial_open(struct inode *inode, struct file *filp)
+{
+	struct cdev *cdev = inode->i_cdev;
+	struct virtio_serial_port *port;
+
+	port = container_of(cdev, struct virtio_serial_port,
+			    cdev);
+
+	filp->private_data = port;
+	return 0;
+}
+
+static unsigned int virtserial_poll(struct file *filp, poll_table *wait)
+{
+	pr_notice("%s\n", __func__);
+	return 0;
+}
+
+static const struct file_operations virtserial_fops = {
+	.owner = THIS_MODULE,
+	.open  = virtserial_open,
+	.read  = virtserial_read,
+	.write = virtserial_write,
+	.compat_ioctl = virtserial_ioctl,
+	.unlocked_ioctl = virtserial_ioctl,
+	.poll  = virtserial_poll,
+	.release = virtserial_release,
+};
+
+static int virtserial_probe(struct virtio_device *vdev)
+{
+	int i, ret;
+	const char *vq_names[] = { "control", "input", "output" };
+	vq_callback_t *vq_callbacks[] = { NULL, receive_data, NULL };
+	struct virtqueue *vqs[3];
+	struct virtio_serial_port *port;
+	struct virtio_serial_config virtsercfg;
+
+	vdev->config->get(vdev, offsetof(struct virtio_serial_config, nr_ports),
+			  &virtsercfg.nr_ports, sizeof(virtsercfg.nr_ports));
+
+	virtserial.vdev = vdev;
+	virtserial.nr_ports = virtsercfg.nr_ports;
+	virtserial.ports = kzalloc(sizeof(struct virtio_serial_port)
+				   * virtserial.nr_ports, GFP_KERNEL);
+	if (!virtserial.ports) {
+		ret = -ENOMEM;
+		goto fail;
+	}
+	ret = vdev->config->find_vqs(vdev, 3, vqs, vq_callbacks, vq_names);
+	if (ret)
+		goto free_vqs;
+
+	virtserial.ctrl_vq = vqs[0];
+	virtserial.in_vq = vqs[1];
+	virtserial.out_vq = vqs[2];
+
+	for (i = 0; i < virtserial.nr_ports; i++) {
+		port = &virtserial.ports[i];
+
+		INIT_LIST_HEAD(&port->readbuf_head);
+
+		cdev_init(&port->cdev, &virtserial_fops);
+		port->dev = MKDEV(major, i);
+
+		/* XXX Do this for each port or do it once? */
+		ret = register_chrdev_region(port->dev, 1, "virtio-serial");
+		if (ret < 0) {
+			pr_err("%s: can't register chrdev region\n",
+			       __func__);
+			goto free_cdev;
+		}
+		ret = cdev_add(&port->cdev, port->dev, 1);
+		if (ret < 0) {
+			pr_err("%s: can't add cdev\n", __func__);
+			goto free_cdev;
+		}
+	}
+	INIT_WORK(&virtserial.rx_work, &virtio_serial_rx_work_handler);
+	INIT_WORK(&virtserial.queue_work, &virtio_serial_queue_work_handler);
+
+	/* Allocate pages to fill the receive queue */
+	schedule_work(&virtserial.queue_work);
+
+	return 0;
+
+free_cdev:
+	unregister_chrdev(major, "virtio-serial");
+free_vqs:
+	vdev->config->del_vqs(vdev);
+fail:
+	return ret;
+}
+
+
+static void virtserial_remove(struct virtio_device *vdev)
+{
+	int len;
+	u32 i;
+	char *buf;
+
+	cancel_work_sync(&virtserial.rx_work);
+	while ((buf = virtserial.in_vq->vq_ops->get_buf(virtserial.in_vq, &len)))
+		kfree(buf);
+
+	vdev->config->del_vqs(vdev);
+
+	unregister_chrdev(major, "virtio-serial");
+	for (i = 0; i < virtserial.nr_ports; i++) {
+		struct virtio_serial_port *port;
+
+		port = &virtserial.ports[i];
+		kfree(port->name);
+	}
+}
+
+static void virtserial_apply_config(struct virtio_device *vdev)
+{
+	struct virtio_serial_config virtserconf;
+
+	vdev->config->get(vdev, offsetof(struct virtio_serial_config, nr_ports),
+			  &virtserconf.nr_ports, sizeof(virtserconf.nr_ports));
+	/* FIXME: hot-add or remove ports */
+}
+
+
+static struct virtio_device_id id_table[] = {
+	{ VIRTIO_ID_SERIAL, VIRTIO_DEV_ANY_ID },
+	{ 0 },
+};
+
+static struct virtio_driver virtio_serial = {
+  //	.feature_table = features,
+  //	.feature_table_size = ARRAY_SIZE(features),
+	.driver.name =	KBUILD_MODNAME,
+	.driver.owner =	THIS_MODULE,
+	.id_table =	id_table,
+	.probe =	virtserial_probe,
+	.remove =	virtserial_remove,
+	.config_changed = virtserial_apply_config,
+};
+
+static int __init init(void)
+{
+	return register_virtio_driver(&virtio_serial);
+}
+
+static void __exit fini(void)
+{
+	unregister_virtio_driver(&virtio_serial);
+}
+module_init(init);
+module_exit(fini);
+
+MODULE_DEVICE_TABLE(virtio, id_table);
+MODULE_DESCRIPTION("Virtio serial driver");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/virtio_serial.h b/include/linux/virtio_serial.h
new file mode 100644
index 0000000..3f33ade
--- /dev/null
+++ b/include/linux/virtio_serial.h
@@ -0,0 +1,42 @@
+#ifndef _LINUX_VIRTIO_SERIAL_H
+#define _LINUX_VIRTIO_SERIAL_H
+#include <linux/types.h>
+#include <linux/virtio_config.h>
+
+/* Guest kernel - Host interface */
+
+/* The ID for virtio serial */
+#define VIRTIO_ID_SERIAL		7
+#define VIRTIO_SERIAL_BAD_ID		(~(u32)0)
+
+struct virtio_serial_config {
+	__u32 nr_ports;
+	__u16 status;
+} __attribute__((packed));
+
+struct virtio_serial_control
+{
+    __u32 port_nr;
+    __u32 key;
+};
+
+/* Some defines for the control channel key */
+#define VIRTIO_SERIAL_GET_PORT_NAME	1
+
+#ifdef __KERNEL__
+
+/* Guest kernel - Guest userspace interface */
+
+/* IOCTL-related */
+#define VIRTIO_SERIAL_IO 0xAF
+
+#define VIRTIO_SERIAL_NAME_MAX_LEN	30
+struct virtio_serial_port_name {
+	char name[VIRTIO_SERIAL_NAME_MAX_LEN];
+};
+
+#define VIRTIO_SERIAL_IOCTL_GET_PORT_NAME	_IOWR(VIRTIO_SERIAL_IO, 0x00, \
+			    struct virtio_serial_port_name)
+
+#endif /* __KERNEL__ */
+#endif /* _LINUX_VIRTIO_SERIAL_H */
-- 
1.6.2.2

[Qemu-devel] [PATCH] virtio-serial: virtio device for simple host <-> guest communication

[Amit Shah]

This interface presents a char device from which bits can be
sent and read.

Sample uses for such a device can be obtaining info from the
guest like the file systems used, apps installed, etc. for
offline usage and logged-in users, clipboard copy-paste, etc.
for online usage.

Signed-off-by: Amit Shah <amit.shah@redhat.com>
---
 Makefile.target    |    2 +-
 hw/pc.c            |   17 +++
 hw/pci.h           |    1 +
 hw/qdev.c          |    6 +-
 hw/virtio-pci.c    |   15 +++
 hw/virtio-serial.c |  354 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 hw/virtio-serial.h |   39 ++++++
 hw/virtio.h        |    1 +
 monitor.c          |    9 ++
 qemu-monitor.hx    |    7 +
 qemu-options.hx    |    8 ++
 sysemu.h           |   11 ++
 vl.c               |   63 +++++++++
 13 files changed, 531 insertions(+), 2 deletions(-)
 create mode 100644 hw/virtio-serial.c
 create mode 100644 hw/virtio-serial.h

diff --git a/Makefile.target b/Makefile.target
index 08121a9..7a0deb3 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -550,7 +550,7 @@ OBJS=vl.o osdep.o monitor.o pci.o loader.o isa_mmio.o machine.o \
      gdbstub.o gdbstub-xml.o
 # virtio has to be here due to weird dependency between PCI and virtio-net.
 # need to fix this properly
-OBJS+=virtio-blk.o virtio-balloon.o virtio-net.o virtio-console.o
+OBJS+=virtio-blk.o virtio-balloon.o virtio-net.o virtio-console.o virtio-serial.o
 ifdef CONFIG_KVM
 OBJS+=kvm.o kvm-all.o
 endif
diff --git a/hw/pc.c b/hw/pc.c
index cb5b4d0..6ccf4b8 100644
--- a/hw/pc.c
+++ b/hw/pc.c
@@ -40,6 +40,8 @@
 
 #include "qemu-kvm.h"
 
+void *virtio_serial_new_port(PCIDevice *dev, int idx, char *name);
+
 /* output Bochs bios info messages */
 //#define DEBUG_BIOS
 
@@ -1204,6 +1206,21 @@ static void pc_init1(ram_addr_t ram_size,
         }
     }
 
+    /* Add virtio serial devices */
+    if (pci_enabled && virtio_serial_index) {
+        void *dev;
+
+        dev = pci_create_simple(pci_bus, -1, "virtio-serial-pci");
+        if (!dev) {
+            fprintf(stderr, "qemu: could not create virtio serial pci device\n");
+            exit(1);
+        }
+
+        for (i = 0; i < virtio_serial_index; i++) {
+                virtio_serial_new_port(dev, i, virtio_serial_names[i]);
+        }
+    }
+
 #ifdef USE_KVM_DEVICE_ASSIGNMENT
     if (kvm_enabled()) {
         add_assigned_devices(pci_bus, assigned_devices, assigned_devices_index);
diff --git a/hw/pci.h b/hw/pci.h
index d835b6d..fe5f29e 100644
--- a/hw/pci.h
+++ b/hw/pci.h
@@ -72,6 +72,7 @@ extern target_phys_addr_t pci_mem_base;
 #define PCI_DEVICE_ID_VIRTIO_BLOCK       0x1001
 #define PCI_DEVICE_ID_VIRTIO_BALLOON     0x1002
 #define PCI_DEVICE_ID_VIRTIO_CONSOLE     0x1003
+#define PCI_DEVICE_ID_VIRTIO_SERIAL      0x1004
 
 typedef void PCIConfigWriteFunc(PCIDevice *pci_dev,
                                 uint32_t address, uint32_t data, int len);
diff --git a/hw/qdev.c b/hw/qdev.c
index 385e709..fe5bcd0 100644
--- a/hw/qdev.c
+++ b/hw/qdev.c
@@ -168,9 +168,13 @@ CharDriverState *qdev_init_chardev(DeviceState *dev)
 {
     static int next_serial;
     static int next_virtconsole;
+    static int next_virtserial;
+
     /* FIXME: This is a nasty hack that needs to go away.  */
-    if (strncmp(dev->type->info->name, "virtio", 6) == 0) {
+    if (strncmp(dev->type->info->name, "virtio-console", 14) == 0) {
         return virtcon_hds[next_virtconsole++];
+    } else if (strncmp(dev->type->info->name, "virtio-serial", 13) == 0) {
+        return virtio_serial_hds[next_virtserial++];
     } else {
         return serial_hds[next_serial++];
     }
diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c
index 24fe837..199f0c6 100644
--- a/hw/virtio-pci.c
+++ b/hw/virtio-pci.c
@@ -334,6 +334,19 @@ static void virtio_balloon_init_pci(PCIDevice *pci_dev)
                     0x00);
 }
 
+static void virtio_serial_init_pci(PCIDevice *pci_dev)
+{
+    VirtIOPCIProxy *proxy = DO_UPCAST(VirtIOPCIProxy, pci_dev, pci_dev);
+    VirtIODevice *vdev;
+
+    vdev = virtio_serial_init(&pci_dev->qdev);
+    virtio_init_pci(proxy, vdev,
+                    PCI_VENDOR_ID_REDHAT_QUMRANET,
+                    PCI_DEVICE_ID_VIRTIO_SERIAL,
+                    PCI_CLASS_COMMUNICATION_OTHER,
+                    0x00);
+}
+
 static void virtio_pci_register_devices(void)
 {
     pci_qdev_register("virtio-blk-pci", sizeof(VirtIOPCIProxy),
@@ -344,6 +357,8 @@ static void virtio_pci_register_devices(void)
                       virtio_console_init_pci);
     pci_qdev_register("virtio-balloon-pci", sizeof(VirtIOPCIProxy),
                       virtio_balloon_init_pci);
+    pci_qdev_register("virtio-serial-pci", sizeof(VirtIOPCIProxy),
+                      virtio_serial_init_pci);
 }
 
 device_init(virtio_pci_register_devices)
diff --git a/hw/virtio-serial.c b/hw/virtio-serial.c
new file mode 100644
index 0000000..5162316
--- /dev/null
+++ b/hw/virtio-serial.c
@@ -0,0 +1,354 @@
+/*
+ * Virtio serial interface
+ *
+ * This serial interface is a paravirtualised guest<->host
+ * communication channel for relaying short messages and events in
+ * either direction.
+ *
+ * There's support for multiple serial channels within one virtio PCI
+ * device to keep the guest PCI device count low.
+ *
+ * Copyright (C) 2009, Red Hat, Inc.
+ *
+ * Author(s): Amit Shah <amit.shah@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ */
+
+#include "hw.h"
+#include "pci.h"
+#include "monitor.h"
+#include "qemu-char.h"
+#include "virtio.h"
+#include "virtio-serial.h"
+#include "sysemu.h"
+
+typedef struct VirtIOSerial {
+    VirtIODevice *vdev;
+    VirtQueue *cvq;
+    VirtQueue *ivq, *ovq;
+    struct VirtIOSerialPort *ports;
+} VirtIOSerial;
+
+typedef struct VirtIOSerialPort {
+    VirtIOSerial *virtserial;
+    CharDriverState *hd;
+    char name[VIRTIO_SERIAL_NAME_MAX_LEN];
+} VirtIOSerialPort;
+
+typedef struct VirtIOSerialId {
+    uint32_t id; /* Port id */
+} VirtIOSerialId;
+
+VirtIOSerial virtio_serial;
+
+static VirtIOSerialPort *get_port_from_id(uint32_t id)
+{
+    if (id > virtio_serial_index)
+        return NULL;
+
+    return &virtio_serial.ports[id];
+}
+
+static char *get_port_name_from_id(uint32_t id)
+{
+    VirtIOSerialPort *port;
+
+    port = get_port_from_id(id);
+    if (port)
+        return port->name;
+    else
+        return NULL;
+}
+
+static int get_id_from_port(VirtIOSerialPort *port)
+{
+    uint32_t i;
+
+    for (i = 0; i < virtio_serial_index; i++) {
+        if (port == &virtio_serial.ports[i]) {
+            return i;
+        }
+    }
+    return VIRTIO_SERIAL_BAD_ID;
+}
+
+static void virtio_serial_handle_control(VirtIODevice *vdev, VirtQueue *vq)
+{
+    VirtQueueElement elem;
+
+    while (virtqueue_pop(vq, &elem)) {
+        int i;
+        char *name;
+        ssize_t len, strlen;
+        struct virtio_serial_control ser_control;
+
+        len = 0;
+        for (i = 0; i < elem.out_num; i++) {
+            memcpy(&ser_control, elem.out_sg[i].iov_base, sizeof(ser_control));
+
+            switch(ser_control.key) {
+            case VIRTIO_SERIAL_GET_PORT_NAME:
+                name = get_port_name_from_id(ser_control.port_nr);
+
+                strlen = strnlen(name, VIRTIO_SERIAL_NAME_MAX_LEN);
+
+                memcpy(elem.in_sg[0].iov_base, &ser_control,
+                       sizeof(ser_control));
+                memcpy(elem.in_sg[0].iov_base + sizeof(ser_control), name,
+                       strlen);
+
+                len = strlen + sizeof(ser_control);
+                break;
+            }
+        }
+        virtqueue_push(vq, &elem, len);
+    }
+    virtio_notify(vdev, vq);
+
+    return;
+}
+
+static void virtio_serial_handle_output(VirtIODevice *vdev, VirtQueue *vq)
+{
+    VirtIOSerialPort *port;
+    VirtQueueElement elem;
+    VirtIOSerialId id;
+
+    while (virtqueue_pop(vq, &elem)) {
+        ssize_t len = 0;
+        int id_len = sizeof(id);
+        int i;
+
+        memcpy(&id, elem.out_sg[0].iov_base, id_len);
+        port = get_port_from_id(id.id);
+
+        if (port->hd) {
+            for (i = 0; i < elem.out_num; i++) {
+                len += qemu_chr_write(port->hd,
+                                      elem.out_sg[i].iov_base + id_len,
+                                      elem.out_sg[i].iov_len - id_len);
+                id_len = 0;
+            }
+        }
+        virtqueue_push(vq, &elem, len);
+    }
+    virtio_notify(vdev, vq);
+}
+
+static void virtio_serial_handle_input(VirtIODevice *vdev, VirtQueue *vq)
+{
+}
+
+
+/* FIXME: we just accept a single string */
+void virtio_serial_send_input(const char *command, const char *key,
+			      const char *value)
+{
+    VirtQueueElement elem;
+    VirtIOSerialPort *s = &virtio_serial.ports[0];
+    VirtIODevice *vdev = s->virtserial->vdev;
+    VirtQueue *vq = s->virtserial->ivq;
+    char buf[300];
+    ssize_t len;
+    int ret;
+    unsigned int i;
+
+    if (!virtio_queue_ready(vq)) {
+        goto queue_not_ready;
+    }
+
+    len = snprintf(buf, 299, "%s %s %s\n", command, key, value);
+
+    /* FIXME! actually handle this in a for loop */
+
+    ret = virtqueue_pop(vq, &elem);
+    if (!ret) {
+        goto queue_not_ready;
+    }
+
+    i = 0;
+    /* Note: We only have PAGE_SIZE sized buffers */
+    memcpy(elem.in_sg[i].iov_base, buf, len);
+    elem.in_sg[i].iov_len = len;
+
+    virtqueue_push(vq, &elem, len);
+    virtio_notify(vdev, vq);
+    return;
+
+queue_not_ready:
+    monitor_printf(cur_mon,
+                   "vmserial: No free virtio buffer found. Message not sent.\n");
+    return;
+}
+
+static int cons_can_read(void *opaque)
+{
+    VirtIOSerialPort *port = (VirtIOSerialPort *) opaque;
+    VirtQueue *vq = port->virtserial->ivq;
+    int size;
+
+    if (!virtio_queue_ready(vq)) {
+        return 0;
+    }
+
+    size = TARGET_PAGE_SIZE;
+    if (virtqueue_avail_bytes(vq, size, 0)) {
+        return size - sizeof(VirtIOSerialId);
+    }
+
+    size = sizeof(VirtIOSerialId) + 1;
+    if (virtqueue_avail_bytes(vq, size, 0)) {
+        return size - sizeof(VirtIOSerialId);
+    }
+    return 0;
+}
+
+static void cons_read(void *opaque, const uint8_t *buf, int size)
+{
+    VirtIOSerialPort *port = (VirtIOSerialPort *) opaque;
+    VirtQueue *vq = port->virtserial->ivq;
+    VirtQueueElement elem;
+    int offset = 0;
+
+    while (offset < size) {
+        VirtIOSerialId id;
+        int i, id_len;
+
+        id_len = sizeof(VirtIOSerialId);
+
+        if (!virtqueue_pop(vq, &elem)) {
+            break;
+        }
+        if (elem.in_sg[0].iov_len < id_len) {
+            /* We can't even store our port number in this buffer. Bug? */
+            fprintf(stderr, "virtio-serial: size %zd less than expected\n",
+                    elem.in_sg[0].iov_len);
+            exit(1);
+        }
+        id.id = cpu_to_le32(get_id_from_port(port));
+        memcpy(elem.in_sg[0].iov_base, &id, id_len);
+
+        for (i = 0; offset < size && i < elem.in_num; i++) {
+            int len = MIN(elem.in_sg[i].iov_len - id_len, size - offset);
+
+            memcpy(elem.in_sg[i].iov_base + id_len, buf + offset, len);
+            offset += len;
+            id_len = 0;
+        }
+        virtqueue_push(vq, &elem, size + sizeof(VirtIOSerialId));
+    }
+    virtio_notify(port->virtserial->vdev, vq);
+}
+
+static void cons_event(void *opaque, int event)
+{
+    /* we will ignore any event for the time being */
+}
+
+static uint32_t virtio_serial_get_features(VirtIODevice *vdev)
+{
+    return 0;
+}
+
+static void virtio_serial_get_config(VirtIODevice *vdev, uint8_t *config_data)
+{
+    struct virtio_serial_config config;
+
+    /* This might have to be updated for serial port hotplug */
+    config.nr_ports = virtio_serial_index;
+    config.status = 0;
+
+    memcpy(config_data, &config, sizeof(config));
+}
+
+static void virtio_serial_set_config(VirtIODevice *vdev,
+                                     const uint8_t *config_data)
+{
+    struct virtio_serial_config config;
+
+    memcpy(&config, config_data, sizeof(config));
+
+    /* Nothing to do as of now */
+}
+
+static void virtio_serial_save(QEMUFile *f, void *opaque)
+{
+    VirtIODevice *vdev = opaque;
+
+    virtio_save(vdev, f);
+}
+
+static int virtio_serial_load(QEMUFile *f, void *opaque, int version_id)
+{
+    VirtIODevice *vdev = opaque;
+
+    if (version_id != 1)
+        return -EINVAL;
+
+    virtio_load(vdev, f);
+    return 0;
+}
+
+void *virtio_serial_new_port(PCIDevice *dev, int idx, char *name)
+{
+    VirtIOSerialPort *port;
+
+    port = &virtio_serial.ports[idx];
+
+    port->virtserial = &virtio_serial;
+
+    memcpy(port->name, name, VIRTIO_SERIAL_NAME_MAX_LEN);
+
+    port->hd = qdev_init_chardev(&dev->qdev);
+    if (port->hd) {
+        qemu_chr_add_handlers(port->hd, cons_can_read, cons_read, cons_event,
+                              port);
+    }
+
+    /* Send an update to the guest about this new port added */
+    virtio_notify_config(port->virtserial->vdev);
+    return port;
+}
+
+VirtIODevice *virtio_serial_init(DeviceState *dev)
+{
+    VirtIODevice *vdev;
+    int nr_ports = 4;
+
+    vdev = virtio_common_init("virtio-serial",
+			      VIRTIO_ID_SERIAL,
+			      sizeof(struct virtio_serial_config),
+			      sizeof(VirtIODevice));
+    if (vdev == NULL)
+        return NULL;
+
+    virtio_serial.vdev = vdev;
+    vdev->get_config = virtio_serial_get_config;
+    vdev->set_config = virtio_serial_set_config;
+    vdev->get_features = virtio_serial_get_features;
+
+    /* Add a queue for control information transfer common to all
+     * serial ports
+     */
+    virtio_serial.cvq = virtio_add_queue(vdev, 2, virtio_serial_handle_control);
+
+    /* Add queue for host to guest transfers */
+    virtio_serial.ivq = virtio_add_queue(vdev, VIRTQUEUE_MAX_SIZE,
+                                         virtio_serial_handle_input);
+    /* Add queue for guest to host transfers */
+    virtio_serial.ovq = virtio_add_queue(vdev, VIRTQUEUE_MAX_SIZE,
+                                         virtio_serial_handle_output);
+
+
+    /* Allocate space for the number of serial ports specified on the
+     * command line
+     */
+    virtio_serial.ports = qemu_mallocz(sizeof(VirtIOSerialPort) * nr_ports);
+
+    register_savevm("virtio-serial", -1, 1, virtio_serial_save,
+                    virtio_serial_load, vdev);
+
+    return vdev;
+}
diff --git a/hw/virtio-serial.h b/hw/virtio-serial.h
new file mode 100644
index 0000000..abbfd0f
--- /dev/null
+++ b/hw/virtio-serial.h
@@ -0,0 +1,39 @@
+/*
+ * Virtio Serial Support
+ *
+ * Copyright (C) 2009, Red Hat, Inc.
+ *
+ * Author(s): Amit Shah <amit.shah@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ *
+ */
+#ifndef _QEMU_VIRTIO_SERIAL_H
+#define _QEMU_VIRTIO_SERIAL_H
+
+/* The ID for virtio serial */
+#define VIRTIO_ID_SERIAL 7
+#define VIRTIO_SERIAL_BAD_ID		(~(uint32_t)0)
+
+struct virtio_serial_config
+{
+    uint32_t nr_ports;
+    uint16_t status;
+} __attribute__((packed));
+
+struct virtio_serial_control
+{
+    uint32_t port_nr;
+    uint32_t key;
+};
+
+/* Some defines for the control channel key */
+#define VIRTIO_SERIAL_GET_PORT_NAME 1
+
+
+void *virtio_serial_new_port(PCIDevice *dev, int idx, char *name);
+void virtio_serial_send_input(const char *command,
+			      const char *key, const char *value);
+
+#endif
diff --git a/hw/virtio.h b/hw/virtio.h
index 425727e..d2b50c3 100644
--- a/hw/virtio.h
+++ b/hw/virtio.h
@@ -151,5 +151,6 @@ VirtIODevice *virtio_blk_init(DeviceState *dev);
 VirtIODevice *virtio_net_init(DeviceState *dev);
 VirtIODevice *virtio_console_init(DeviceState *dev);
 VirtIODevice *virtio_balloon_init(DeviceState *dev);
+VirtIODevice *virtio_serial_init(DeviceState *dev);
 
 #endif
diff --git a/monitor.c b/monitor.c
index 8d5165c..7cb896e 100644
--- a/monitor.c
+++ b/monitor.c
@@ -45,6 +45,7 @@
 #include "kvm.h"
 #include "acl.h"
 #include "exec-all.h"
+#include "hw/virtio-serial.h"
 
 #include "qemu-kvm.h"
 
@@ -1683,6 +1684,14 @@ static void do_acl(Monitor *mon,
     }
 }
 
+static void do_virtio_serial_action(Monitor *mon,
+                                    const char *command,
+                                    const char *key,
+                                    const char *value)
+{
+    virtio_serial_send_input(command, key, value);
+}
+
 static const mon_cmd_t mon_cmds[] = {
 #include "qemu-monitor.h"
     { NULL, NULL, },
diff --git a/qemu-monitor.hx b/qemu-monitor.hx
index dea0704..e1c3eb3 100644
--- a/qemu-monitor.hx
+++ b/qemu-monitor.hx
@@ -567,6 +567,13 @@ STEXI
 Change watchdog action.
 ETEXI
 
+    { "virtio-serial", "sss", do_virtio_serial_action,
+      "<command> <key> <value>\n", "virtio-serial write get clipboard\n" },
+STEXI
+@item virtio-serial
+Send data to virtio-serial port
+ETEXI
+
     { "acl", "sss?i?", do_acl, "<command> <aclname> [<match> [<index>]]\n",
                                "acl show vnc.username\n"
                                "acl policy vnc.username deny\n"
diff --git a/qemu-options.hx b/qemu-options.hx
index c5aed0e..9c9f767 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -1533,6 +1533,14 @@ STEXI
 Set virtio console.
 ETEXI
 
+DEF("virtioserial", HAS_ARG, QEMU_OPTION_virtioserial, \
+    "-virtioserial c\n" \
+    "                define virtio serial device\n")
+STEXI
+@item -virtserial @var{c}
+Set virtio serial device.
+ETEXI
+
 DEF("show-cursor", 0, QEMU_OPTION_show_cursor, \
     "-show-cursor    show cursor\n")
 STEXI
diff --git a/sysemu.h b/sysemu.h
index 686228d..a0501d2 100644
--- a/sysemu.h
+++ b/sysemu.h
@@ -234,6 +234,17 @@ extern CharDriverState *parallel_hds[MAX_PARALLEL_PORTS];
 
 extern CharDriverState *virtcon_hds[MAX_VIRTIO_CONSOLES];
 
+/* virtio serial ports */
+
+#define MAX_VIRTIO_SERIAL_PORTS 4
+#define VIRTIO_SERIAL_NAME_MAX_LEN 30
+
+
+extern CharDriverState *virtio_serial_hds[MAX_VIRTIO_SERIAL_PORTS];
+extern char virtio_serial_names[MAX_VIRTIO_SERIAL_PORTS][VIRTIO_SERIAL_NAME_MAX_LEN];
+extern int virtio_serial_index;
+
+
 #define TFR(expr) do { if ((expr) != -1) break; } while (errno == EINTR)
 
 #ifdef NEED_CPU_H
diff --git a/vl.c b/vl.c
index 7278999..a078588 100644
--- a/vl.c
+++ b/vl.c
@@ -237,6 +237,9 @@ int no_quit = 0;
 CharDriverState *serial_hds[MAX_SERIAL_PORTS];
 CharDriverState *parallel_hds[MAX_PARALLEL_PORTS];
 CharDriverState *virtcon_hds[MAX_VIRTIO_CONSOLES];
+CharDriverState *virtio_serial_hds[MAX_VIRTIO_SERIAL_PORTS];
+char virtio_serial_names[MAX_VIRTIO_SERIAL_PORTS][VIRTIO_SERIAL_NAME_MAX_LEN];
+int virtio_serial_index;
 #ifdef TARGET_I386
 int win2k_install_hack = 0;
 int rtc_td_hack = 0;
@@ -5039,6 +5042,7 @@ int main(int argc, char **argv, char **envp)
     int parallel_device_index;
     const char *virtio_consoles[MAX_VIRTIO_CONSOLES];
     int virtio_console_index;
+    const char *virtio_serials[MAX_VIRTIO_SERIAL_PORTS];
     const char *loadvm = NULL;
     QEMUMachine *machine;
     const char *cpu_model;
@@ -5118,6 +5122,10 @@ int main(int argc, char **argv, char **envp)
         virtio_consoles[i] = NULL;
     virtio_console_index = 0;
 
+    for (i = 0; i < MAX_VIRTIO_SERIAL_PORTS; i++)
+        virtio_serials[i] = NULL;
+    virtio_serial_index = 0;
+
     for (i = 0; i < MAX_NODES; i++) {
         node_mem[i] = 0;
         node_cpumask[i] = 0;
@@ -5548,6 +5556,14 @@ int main(int argc, char **argv, char **envp)
                 virtio_consoles[virtio_console_index] = optarg;
                 virtio_console_index++;
                 break;
+	    case QEMU_OPTION_virtioserial:
+                if (virtio_serial_index >= MAX_VIRTIO_SERIAL_PORTS) {
+                    fprintf(stderr, "qemu: too many virtio serial ports\n");
+                    exit(1);
+                }
+                virtio_serials[virtio_serial_index] = optarg;
+                virtio_serial_index++;
+                break;
             case QEMU_OPTION_parallel:
                 if (parallel_device_index >= MAX_PARALLEL_PORTS) {
                     fprintf(stderr, "qemu: too many parallel ports\n");
@@ -6209,6 +6225,44 @@ int main(int argc, char **argv, char **envp)
         }
     }
 
+    for (i = 0; i < virtio_serial_index; i++) {
+        const char *virtseropt;
+        char devname[80];
+        int j, k;
+
+        memset(devname, 0, 80);
+        j = k = 0;
+        while (isalnum(virtio_serials[i][j])) {
+            devname[k] = virtio_serials[i][j];
+            k++;
+            j++;
+        }
+
+        if (devname[0] && strncmp(devname, "none", 4)) {
+            char label[32];
+            snprintf(label, sizeof(label), "virtio-serial%d", i);
+            virtio_serial_hds[i] = qemu_chr_open(label, devname, NULL);
+            if (!virtio_serial_hds[i]) {
+                fprintf(stderr, "qemu: could not open virtio serial '%s'\n",
+                        devname);
+                exit(1);
+            }
+        }
+        virtseropt = strstr(virtio_serials[i], ",name=");
+        if (virtseropt) {
+            int j, k = 6;
+
+            for (j = 0; j < VIRTIO_SERIAL_NAME_MAX_LEN && isalnum(virtseropt[k]);
+                 j++, k++) {
+                virtio_serial_names[i][j] = virtseropt[k];
+            }
+            if (j < VIRTIO_SERIAL_NAME_MAX_LEN - 1) {
+                virtio_serial_names[i][j + 1] = 0;
+            }
+        }
+
+    }
+
     module_call_init(MODULE_INIT_DEVICE);
 
     if (kvm_enabled())
@@ -6340,6 +6394,15 @@ int main(int argc, char **argv, char **envp)
         }
     }
 
+    for(i = 0; i < MAX_VIRTIO_SERIAL_PORTS; i++) {
+        const char *devname = virtio_serials[i];
+        if (virtio_serial_hds[i] && devname) {
+            if (strstart(devname, "vc", 0)) {
+                qemu_chr_printf(virtio_serial_hds[i], "virtio serial%d\r\n", i);
+            }
+        }
+    }
+
     if (gdbstub_dev && gdbserver_start(gdbstub_dev) < 0) {
         fprintf(stderr, "qemu: could not open gdbserver on device '%s'\n",
                 gdbstub_dev);
-- 
1.6.2.2

Re: [Qemu-devel] virtio-serial: A guest <-> host interface for simple communication

[Paul Brook]

> Here are two patches. One implements a virtio-serial device in qemu
> and the other is the driver for a guest kernel.

So I'll ask again. Why is this separate from virtio-console?

Paul

Re: [Qemu-devel] virtio-serial: A guest <-> host interface for simple communication

[Amit Shah]

On (Tue) Jun 23 2009 [13:55:52], Paul Brook wrote:
> > Here are two patches. One implements a virtio-serial device in qemu
> > and the other is the driver for a guest kernel.
> 
> So I'll ask again. Why is this separate from virtio-console?

I'm basically writing a vmchannel and found out that a lot can be shared
between some virtio devices. So I'm just trying to abstract out those
things in virtio-serial. Once we're sure virtio-serial is good and ready
to be merged, I will look at converting over virtio-console to the
virtio-serial interface.

Is that an acceptable approach?

Thanks,
		Amit

Re: [Qemu-devel] virtio-serial: A guest <-> host interface for simple communication

[Paul Brook]

On Tuesday 23 June 2009, Amit Shah wrote:
> On (Tue) Jun 23 2009 [13:55:52], Paul Brook wrote:
> > > Here are two patches. One implements a virtio-serial device in qemu
> > > and the other is the driver for a guest kernel.
> >
> > So I'll ask again. Why is this separate from virtio-console?
>
> I'm basically writing a vmchannel and found out that a lot can be shared
> between some virtio devices. So I'm just trying to abstract out those
> things in virtio-serial. Once we're sure virtio-serial is good and ready
> to be merged, I will look at converting over virtio-console to the
> virtio-serial interface.

That doesn't really answer my question. We already have a virtual serial 
device (called virtio-console). Why are you inventing another one?

Paul

Re: [Qemu-devel] virtio-serial: A guest <-> host interface for simple communication

[Christian Bornträger]

Am Dienstag 23 Juni 2009 14:55:52 schrieb Paul Brook:
> > Here are two patches. One implements a virtio-serial device in qemu
> > and the other is the driver for a guest kernel.
>
> So I'll ask again. Why is this separate from virtio-console?

I did some work on virtio-console, since kvm on s390 does not provide any other.
I dont think we should mix two different types of devices into one driver. The 
only thing that these drivers have in common, is the fact that there are two 
virtqueues, piping data (single bytes or larger chunks). So you could make the 
same argument with the first virtio_net driver (the one before GSO) - which is 
obviously wrong. The common part of the transport is already factored out to 
virtio_ring and the transports.

In addition there are two ABIs involved: a userspace ABI (/dev/hvc0) and a 
guest/host ABI for this console. (and virtio was not meant to be a KVM-only 
interface, that we can change all the time). David A. Wheeler's 'SLOCCount' 
gives me 141 lines of code for virtio_console.c. I am quite confident that the 
saving we could achieve by merging these two drivers is not worth the hazzle.

Discussion about merging the console code into this distracts from the main 
problem: To get the interface and functionality right before it becomes an ABI 
(is it /dev/ttyS, network like or is it something completely different?).

Christian

Re: [Qemu-devel] virtio-serial: A guest <-> host interface for simple communication

[Paul Brook]

On Tuesday 23 June 2009, Christian Bornträger wrote:
> Am Dienstag 23 Juni 2009 14:55:52 schrieb Paul Brook:
> > > Here are two patches. One implements a virtio-serial device in qemu
> > > and the other is the driver for a guest kernel.
> >
> > So I'll ask again. Why is this separate from virtio-console?
>
> I did some work on virtio-console, since kvm on s390 does not provide any
> other. I dont think we should mix two different types of devices into one
> driver. The only thing that these drivers have in common, is the fact that
> there are two virtqueues, piping data (single bytes or larger chunks). So
> you could make the same argument with the first virtio_net driver (the one
> before GSO) - which is obviously wrong. The common part of the transport is
> already factored out to virtio_ring and the transports.

virtio-net is packet based, not stream based.

> In addition there are two ABIs involved: a userspace ABI (/dev/hvc0) and a
> guest/host ABI for this console. (and virtio was not meant to be a KVM-only
> interface, that we can change all the time). David A. Wheeler's 'SLOCCount'
> gives me 141 lines of code for virtio_console.c. I am quite confident that
> the saving we could achieve by merging these two drivers is not worth the
> hazzle.

AFAICS the functionality provided is exactly the same. The host API is 
identical, and the guest userspace API only has trivial differences (which 
could be eliminated with a simple udev rule). By my reading virtio-serial 
makes virtio-console entirely redundant.

> Discussion about merging the console code into this distracts from the main
> problem: To get the interface and functionality right before it becomes an
> ABI (is it /dev/ttyS, network like or is it something completely
> different?).

Ah, now that's a different question. I don't know what the requirements are 
for the higher level vmchannel interface. However I also don't care.

Paul

Re: [Qemu-devel] virtio-serial: A guest <-> host interface for simple communication

[Christian Bornträger]

Am Dienstag 23 Juni 2009 16:16:13 schrieb Paul Brook:
> > I did some work on virtio-console, since kvm on s390 does not provide any
> > other. I dont think we should mix two different types of devices into one
> > driver. The only thing that these drivers have in common, is the fact
> > that there are two virtqueues, piping data (single bytes or larger
> > chunks). So you could make the same argument with the first virtio_net
> > driver (the one before GSO) - which is obviously wrong. The common part
> > of the transport is already factored out to virtio_ring and the
> > transports.
>
> virtio-net is packet based, not stream based.

You can argue that virtio-console is also packet based. The input buffer can 
accept up to 4K in one buffer and the console code can also submit larger chunks 
to virtio_console.

> > In addition there are two ABIs involved: a userspace ABI (/dev/hvc0) and
> > a guest/host ABI for this console. (and virtio was not meant to be a
> > KVM-only interface, that we can change all the time). David A. Wheeler's
> > 'SLOCCount' gives me 141 lines of code for virtio_console.c. I am quite
> > confident that the saving we could achieve by merging these two drivers
> > is not worth the hazzle.
>
> AFAICS the functionality provided is exactly the same. The host API is
> identical, and the guest userspace API only has trivial differences (which
> could be eliminated with a simple udev rule). By my reading virtio-serial
> makes virtio-console entirely redundant.

How can you know, that the userspace API only has trivial differences, if the 
question below is not answered?

> > Discussion about merging the console code into this distracts from the
> > main problem: To get the interface and functionality right before it
> > becomes an ABI (is it /dev/ttyS, network like or is it something
> > completely different?).
>
> Ah, now that's a different question. I don't know what the requirements are
> for the higher level vmchannel interface. However I also don't care.

You should care, because it might have an impact if two serial lines are really 
the right solution for the vmchannel.

One thing that I forgot:
You should be warned that hvc_console sometimes can be a real PITA. A while ago 
I tried to change virtio_console to support more than one console and hotplug 
and failed to find a proper solution that can handle all the subtle  console/tty 
register/unregister combinations. You dont want to adopt new code to fit to 
hvc_console - leave it in virtio_console...

Re: [Qemu-devel] virtio-serial: A guest <-> host interface for simple communication

[Daniel P. Berrange]

On Tue, Jun 23, 2009 at 01:55:52PM +0100, Paul Brook wrote:
> > Here are two patches. One implements a virtio-serial device in qemu
> > and the other is the driver for a guest kernel.
> 
> So I'll ask again. Why is this separate from virtio-console?

In the guest I wouldn't want virtio-serial devices to be mixed up with
the virtio-console device. virtio-console has nice clear usecase of
being an interactive console, and as such the guest OS can & should 
automatically start a mingetty/agetty process on any virtio-console
device it finds.  If we use virtio-console for data channels to, then
guest config becomes much harder todo automatically.

By all means share underlying code/infrastructure where appropriate,
but they must ultimately appear as clearly separate devices IMHO

Daniel
-- 
|: Red Hat, Engineering, London   -o-   http://people.redhat.com/berrange/ :|
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|: GnuPG: 7D3B9505  -o-  F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|

Re: [Qemu-devel] [PATCH] virtio_serial: A char device for simple guest <-> host communication

[Blue Swirl]

On 6/23/09, Amit Shah <amit.shah@redhat.com> wrote:
> We expose multiple char devices ("ports") for simple communication
>  between the host userspace and guest.
>  +struct virtio_serial_config {
>  +       __u32 nr_ports;
>  +       __u16 status;
>  +} __attribute__((packed));

There is still structure packing. I'd use __u16 for both fields, do
you really need 4 gigs of ports?.

Re: [Qemu-devel] [PATCH] virtio-serial: virtio device for simple host <-> guest communication

[Blue Swirl]

On 6/23/09, Amit Shah <amit.shah@redhat.com> wrote:
> This interface presents a char device from which bits can be
>  sent and read.

>  +struct virtio_serial_config
>  +{
>  +    uint32_t nr_ports;
>  +    uint16_t status;
>  +} __attribute__((packed));

Obviously this has to match the kernel structure if you go for 16 bit nr_ports.

[Qemu-devel] Re: virtio-serial: A guest <-> host interface for simple communication

[Rusty Russell]

On Tue, 23 Jun 2009 10:12:31 pm Amit Shah wrote:
> Hello,
>
> Here are two patches. One implements a virtio-serial device in qemu
> and the other is the driver for a guest kernel.
>
> While working on a vmchannel interface that is needed for communication
> between guest userspace and host userspace, I saw that most of the
> interface can be abstracted out as a "serial" device with "ports".

OK, I don't think the "naming" idea works though.  A userspace user would have 
to open each one in turn to get its name.  I'd stick with numbers.

You also don't have dynamic creation and removal, except by hotpluging the 
entire device (which was on your requirements page).

I'd put a size and bitmap in the configuration space, and use that to indicate 
what ports exist.  Register on the change interrupt to get updates.  Drop the 
control vq entirely.

Cheers,
Rusty.

[Qemu-devel] Re: virtio-serial: A guest <-> host interface for simple communication

[Amit Shah]

On (Wed) Jun 24 2009 [13:45:01], Rusty Russell wrote:
> On Tue, 23 Jun 2009 10:12:31 pm Amit Shah wrote:
> > Hello,
> >
> > Here are two patches. One implements a virtio-serial device in qemu
> > and the other is the driver for a guest kernel.
> >
> > While working on a vmchannel interface that is needed for communication
> > between guest userspace and host userspace, I saw that most of the
> > interface can be abstracted out as a "serial" device with "ports".
> 
> OK, I don't think the "naming" idea works though.  A userspace user would have 
> to open each one in turn to get its name.  I'd stick with numbers.

What if an ioctl were added to get the port number from the port name?
Userspace would do
	ioctl(fd, VIRTIO_SERIAL_GET_PORT_FROM_NAME, &nr);
	sprintf(port, "/dev/vmch%s", nr);
	fd2 = open(port, ...);

?

> You also don't have dynamic creation and removal, except by hotpluging the 
> entire device (which was on your requirements page).

Actually we're more interested in hotplugging ports than the device
itself ("Dynamic channel creation").

> what ports exist.  Register on the change interrupt to get updates.  Drop the 
> control vq entirely.

If the ioctl mentioned above were added, it would justify the control
vq, right?

Thanks for the comments,
		Amit

Re: [Qemu-devel] virtio-serial: A guest <-> host interface for simple communication

[Jamie Lokier]

Amit Shah wrote:
> A few sample uses for a vmchannel are to share the host and guest
> clipboards (to allow copy/paste between a host and a guest), to
> lock the screen of the guest session when the vnc viewer is closed,
> to find out which applications are installed on a guest OS even when
> the guest is powered down (using virt-inspector) and so on.

Those all look like useful features.

Can you run an application to provide those features on a guest which
_doesn't_ have a vmchannel/virtio-serial support in the kernel?

Or will it be restricted only to guests which have QEMU-specific
support in their kernel?

-- Jamie

Re: [Qemu-devel] virtio-serial: A guest <-> host interface for simple communication

[Amit Shah]

On (Wed) Jun 24 2009 [17:40:49], Jamie Lokier wrote:
> Amit Shah wrote:
> > A few sample uses for a vmchannel are to share the host and guest
> > clipboards (to allow copy/paste between a host and a guest), to
> > lock the screen of the guest session when the vnc viewer is closed,
> > to find out which applications are installed on a guest OS even when
> > the guest is powered down (using virt-inspector) and so on.
> 
> Those all look like useful features.
> 
> Can you run an application to provide those features on a guest which
> _doesn't_ have a vmchannel/virtio-serial support in the kernel?
> 
> Or will it be restricted only to guests which have QEMU-specific
> support in their kernel?

libguestfs currently uses the -net user based vmchannel interface that
exists in current qemu. That doesn't need a kernel that doesn't have
support for virtio-serial.

		Amit

Re: [Qemu-devel] virtio-serial: A guest <-> host interface for simple communication

[Jamie Lokier]

Amit Shah wrote:
> On (Wed) Jun 24 2009 [17:40:49], Jamie Lokier wrote:
> > Amit Shah wrote:
> > > A few sample uses for a vmchannel are to share the host and guest
> > > clipboards (to allow copy/paste between a host and a guest), to
> > > lock the screen of the guest session when the vnc viewer is closed,
> > > to find out which applications are installed on a guest OS even when
> > > the guest is powered down (using virt-inspector) and so on.
> > 
> > Those all look like useful features.
> > 
> > Can you run an application to provide those features on a guest which
> > _doesn't_ have a vmchannel/virtio-serial support in the kernel?
> > 
> > Or will it be restricted only to guests which have QEMU-specific
> > support in their kernel?
> 
> libguestfs currently uses the -net user based vmchannel interface that
> exists in current qemu. That doesn't need a kernel that doesn't have
> support for virtio-serial.

That's great!

If that works fine, and guest apps/libraries are using that as a
fallback anyway, what benefit do they get from switching to
virtio-serial when they detect that instead, given they still have
code for the -net method?

Is the plan to remove -net user based support from libguestfs?

Is virtio-serial significantly simpler to use?

-- Jamie

Re: [Qemu-devel] virtio-serial: A guest <-> host interface for simple communication

[Amit Shah]

On (Wed) Jun 24 2009 [18:50:02], Jamie Lokier wrote:
> Amit Shah wrote:
> > On (Wed) Jun 24 2009 [17:40:49], Jamie Lokier wrote:
> > > Amit Shah wrote:
> > > > A few sample uses for a vmchannel are to share the host and guest
> > > > clipboards (to allow copy/paste between a host and a guest), to
> > > > lock the screen of the guest session when the vnc viewer is closed,
> > > > to find out which applications are installed on a guest OS even when
> > > > the guest is powered down (using virt-inspector) and so on.
> > > 
> > > Those all look like useful features.
> > > 
> > > Can you run an application to provide those features on a guest which
> > > _doesn't_ have a vmchannel/virtio-serial support in the kernel?
> > > 
> > > Or will it be restricted only to guests which have QEMU-specific
> > > support in their kernel?
> > 
> > libguestfs currently uses the -net user based vmchannel interface that
> > exists in current qemu. That doesn't need a kernel that doesn't have
> > support for virtio-serial.
> 
> That's great!
> 
> If that works fine, and guest apps/libraries are using that as a
> fallback anyway, what benefit do they get from switching to
> virtio-serial when they detect that instead, given they still have
> code for the -net method?

Speed is the biggest benefit.

> Is the plan to remove -net user based support from libguestfs?

I don't know what Richard's plan is, but if the kernel that libguestfs
deploys in the appliance gains support for virtio-serial, there's no
reason it shouldn't switch.

> Is virtio-serial significantly simpler to use?

I think the interface from the guest POV stays the same: reads / writes
to char devices. With virtio-serial, though, we can add a few other
interesting things like names to ports, ability to hot-add ports on
demand, request notifications when either end goes down, etc.

		Amit

Re: [Qemu-devel] virtio-serial: A guest <-> host interface for simple communication

[Jamie Lokier]

Amit Shah wrote:
> On (Wed) Jun 24 2009 [18:50:02], Jamie Lokier wrote:
> > Amit Shah wrote:
> > > On (Wed) Jun 24 2009 [17:40:49], Jamie Lokier wrote:
> > > > Amit Shah wrote:
> > > > > A few sample uses for a vmchannel are to share the host and guest
> > > > > clipboards (to allow copy/paste between a host and a guest), to
> > > > > lock the screen of the guest session when the vnc viewer is closed,
> > > > > to find out which applications are installed on a guest OS even when
> > > > > the guest is powered down (using virt-inspector) and so on.
> > > > 
> > > > Those all look like useful features.
> > > > 
> > > > Can you run an application to provide those features on a guest which
> > > > _doesn't_ have a vmchannel/virtio-serial support in the kernel?
> > > > 
> > > > Or will it be restricted only to guests which have QEMU-specific
> > > > support in their kernel?
> > > 
> > > libguestfs currently uses the -net user based vmchannel interface that
> > > exists in current qemu. That doesn't need a kernel that doesn't have
> > > support for virtio-serial.
> > 
> > That's great!
> > 
> > If that works fine, and guest apps/libraries are using that as a
> > fallback anyway, what benefit do they get from switching to
> > virtio-serial when they detect that instead, given they still have
> > code for the -net method?
> 
> Speed is the biggest benefit.

Fair enough, sounds good, and I can see how it's more usable than a
network interface in many respects.

> > Is the plan to remove -net user based support from libguestfs?
> 
> I don't know what Richard's plan is, but if the kernel that libguestfs
> deploys in the appliance gains support for virtio-serial, there's no
> reason it shouldn't switch.
> 
> > Is virtio-serial significantly simpler to use?
> 
> I think the interface from the guest POV stays the same: reads / writes
> to char devices. With virtio-serial, though, we can add a few other
> interesting things like names to ports, ability to hot-add ports on
> demand, request notifications when either end goes down, etc.

Good features, useful for a lot of handy things.  I think it would be
handy if the same features were available to the guest application
generally, not just on guest kernels with a specific driver though.

As we talked before, about things like boot loaders and kernel
debuggers, and installing the support applications on old guests.

Is it possible to support access to the same capabilities through a
well known IO/MMIO address, in the same way that VGA and IDE are both
ordinary PCI devices, but also can be reached easily through well
known IO/MMIO addresses in simple code?

-- Jamie

Re: [Qemu-devel] virtio-serial: A guest <-> host interface for simple communication

[Amit Shah]

On (Wed) Jun 24 2009 [20:20:27], Jamie Lokier wrote:
> Amit Shah wrote:
> > 
> > I think the interface from the guest POV stays the same: reads / writes
> > to char devices. With virtio-serial, though, we can add a few other
> > interesting things like names to ports, ability to hot-add ports on
> > demand, request notifications when either end goes down, etc.
> 
> Good features, useful for a lot of handy things.  I think it would be
> handy if the same features were available to the guest application
> generally, not just on guest kernels with a specific driver though.
> 
> As we talked before, about things like boot loaders and kernel
> debuggers, and installing the support applications on old guests.

The -net vmchannel offers that option. Can't see how to do it other way.

> Is it possible to support access to the same capabilities through a
> well known IO/MMIO address, in the same way that VGA and IDE are both
> ordinary PCI devices, but also can be reached easily through well
> known IO/MMIO addresses in simple code?

The exits caused by accessing IO/MMIO regions are costlier than using
PV. So using the current vmchannel option would be almost similar in
those respects.

Also, virtio is the almost standard way these days to get performance.
We already have block, net drivers over virtio and they have been ported
to older kernels as well.

		Amit

[Qemu-devel] Re: virtio-serial: A guest <-> host interface for simple communication

[Rusty Russell]

On Wed, 24 Jun 2009 10:09:37 pm Amit Shah wrote:
> On (Wed) Jun 24 2009 [13:45:01], Rusty Russell wrote:
> > On Tue, 23 Jun 2009 10:12:31 pm Amit Shah wrote:
> > > Hello,
> > >
> > > Here are two patches. One implements a virtio-serial device in qemu
> > > and the other is the driver for a guest kernel.
> > >
> > > While working on a vmchannel interface that is needed for communication
> > > between guest userspace and host userspace, I saw that most of the
> > > interface can be abstracted out as a "serial" device with "ports".
> >
> > OK, I don't think the "naming" idea works though.  A userspace user would
> > have to open each one in turn to get its name.  I'd stick with numbers.
>
> What if an ioctl were added to get the port number from the port name?
> Userspace would do
> 	ioctl(fd, VIRTIO_SERIAL_GET_PORT_FROM_NAME, &nr);
> 	sprintf(port, "/dev/vmch%s", nr);
> 	fd2 = open(port, ...);

Yep, pretty ugly tho.  If you use the "Amit Shah is in charge of port 
numbering approach", then it's just:

	fd = open("/dev/vmch<my-assigned-number>", ...);

Since you need to control names anyway, why not just use numbers?

> > You also don't have dynamic creation and removal, except by hotpluging
> > the entire device (which was on your requirements page).
>
> Actually we're more interested in hotplugging ports than the device
> itself ("Dynamic channel creation").

Exactly, which you don't seem to have.

> > what ports exist.  Register on the change interrupt to get updates.  Drop
> > the control vq entirely.
>
> If the ioctl mentioned above were added, it would justify the control
> vq, right?

Yes.  Or put another way, simplifying the interface to use assigned port 
numbers would simplify the implementation, use, and specification of the device 
:)

Cheers,
Rusty.

[Qemu-devel] Re: virtio-serial: A guest <-> host interface for simple communication

[Amit Shah]

On (Thu) Jun 25 2009 [21:03:02], Rusty Russell wrote:
> On Wed, 24 Jun 2009 10:09:37 pm Amit Shah wrote:
> > On (Wed) Jun 24 2009 [13:45:01], Rusty Russell wrote:
> > > On Tue, 23 Jun 2009 10:12:31 pm Amit Shah wrote:
> > > > Hello,
> > > >
> > > > Here are two patches. One implements a virtio-serial device in qemu
> > > > and the other is the driver for a guest kernel.
> > > >
> > > > While working on a vmchannel interface that is needed for communication
> > > > between guest userspace and host userspace, I saw that most of the
> > > > interface can be abstracted out as a "serial" device with "ports".
> > >
> > > OK, I don't think the "naming" idea works though.  A userspace user would
> > > have to open each one in turn to get its name.  I'd stick with numbers.
> >
> > What if an ioctl were added to get the port number from the port name?
> > Userspace would do
> > 	ioctl(fd, VIRTIO_SERIAL_GET_PORT_FROM_NAME, &nr);
> > 	sprintf(port, "/dev/vmch%s", nr);
> > 	fd2 = open(port, ...);
> 
> Yep, pretty ugly tho.  If you use the "Amit Shah is in charge of port 
> numbering approach", then it's just:
> 
> 	fd = open("/dev/vmch<my-assigned-number>", ...);
> 
> Since you need to control names anyway, why not just use numbers?

That's a very interesting idea.

(But do we need such formal naming? Are the apps going to need such an
elaborate arrangement?)

> > > You also don't have dynamic creation and removal, except by hotpluging
> > > the entire device (which was on your requirements page).
> >
> > Actually we're more interested in hotplugging ports than the device
> > itself ("Dynamic channel creation").
> 
> Exactly, which you don't seem to have.

You just challenged my laziness and todo list. See the new patch below ;-)

> > > what ports exist.  Register on the change interrupt to get updates.  Drop
> > > the control vq entirely.
> >
> > If the ioctl mentioned above were added, it would justify the control
> > vq, right?
> 
> Yes.  Or put another way, simplifying the interface to use assigned port 
> numbers would simplify the implementation, use, and specification of the device 

I agree. Let me think over this more. I'll also invite comments from
others.

		Amit


diff --git a/drivers/char/Kconfig b/drivers/char/Kconfig
index 0bd01f4..4af76c7 100644
--- a/drivers/char/Kconfig
+++ b/drivers/char/Kconfig
@@ -679,6 +679,12 @@ config VIRTIO_CONSOLE
 	help
 	  Virtio console for use with lguest and other hypervisors.
 
+config VIRTIO_SERIAL
+	tristate "Virtio serial"
+	select VIRTIO
+	select VIRTIO_RING
+	help
+	  Virtio serial device driver for simple guest and host communication
 
 config HVCS
 	tristate "IBM Hypervisor Virtual Console Server support"
diff --git a/drivers/char/Makefile b/drivers/char/Makefile
index 189efcf..0b6c71e 100644
--- a/drivers/char/Makefile
+++ b/drivers/char/Makefile
@@ -54,6 +54,7 @@ obj-$(CONFIG_HVC_XEN)		+= hvc_xen.o
 obj-$(CONFIG_HVC_IUCV)		+= hvc_iucv.o
 obj-$(CONFIG_HVC_UDBG)		+= hvc_udbg.o
 obj-$(CONFIG_VIRTIO_CONSOLE)	+= virtio_console.o
+obj-$(CONFIG_VIRTIO_SERIAL)	+= virtio_serial.o
 obj-$(CONFIG_RAW_DRIVER)	+= raw.o
 obj-$(CONFIG_SGI_SNSC)		+= snsc.o snsc_event.o
 obj-$(CONFIG_MSPEC)		+= mspec.o
diff --git a/drivers/char/virtio_serial.c b/drivers/char/virtio_serial.c
new file mode 100644
index 0000000..4439697
--- /dev/null
+++ b/drivers/char/virtio_serial.c
@@ -0,0 +1,645 @@
+/*
+ * VirtIO Serial driver
+ *
+ * This is paravirtualised serial guest<->host communication channel
+ * for relaying short messages and events in either direction.
+ *
+ * One PCI device can have multiple serial ports so that different
+ * applications can communicate without polluting the PCI device space
+ * in the guest.
+ *
+ * Copyright (C) 2009, Red Hat, Inc.
+ *
+ * Author(s): Amit Shah <amit.shah@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+
+#include <linux/cdev.h>
+#include <linux/completion.h>
+#include <linux/err.h>
+#include <linux/fs.h>
+#include <linux/init.h>
+#include <linux/poll.h>
+#include <linux/virtio.h>
+#include <linux/virtio_serial.h>
+#include <linux/workqueue.h>
+
+struct virtio_serial_struct {
+	struct work_struct rx_work;
+	struct work_struct tx_work;
+	struct work_struct queue_work;
+
+	struct list_head port_head;
+
+	struct virtio_device *vdev;
+	struct virtqueue *ctrl_vq;
+	struct virtqueue *in_vq, *out_vq;
+
+	u32 nr_ports;
+};
+
+/* This struct holds individual buffers received for each port */
+struct virtio_serial_port_buffer {
+	struct list_head list;
+
+	unsigned int len; /* length of the buffer */
+	unsigned int offset; /* offset in the buf from which to consume data */
+
+	char *buf;
+};
+
+/* This struct is put in each buffer that gets passed to userspace and
+ * vice-versa
+ */
+struct virtio_serial_id {
+	u32 id; /* Port number */
+};
+
+struct virtio_serial_port {
+	/* The name given to this channel, if any. NOT zero-terminated */
+	char *name;
+
+	/* Next port in the list */
+	struct list_head next;
+
+	/* Buffer management */
+	struct virtio_serial_port_buffer read_buf;
+	struct list_head readbuf_head;
+	struct completion have_data;
+
+	/* Each port associates with a separate char device */
+	dev_t dev;
+	struct cdev cdev;
+
+	/* The number of this port */
+	u32 nr;
+};
+
+static struct virtio_serial_struct virtserial;
+
+static int major = 60; /* from the experimental range */
+
+static int request_control_info(struct virtio_serial_control *ser_control);
+
+static struct virtio_serial_port *get_port_from_id(u32 id)
+{
+	struct virtio_serial_port *port;
+	struct list_head *ptr;
+
+	list_for_each(ptr, &virtserial.port_head) {
+		port = list_entry(ptr, struct virtio_serial_port, next);
+
+		if (port->nr == id)
+			return port;
+	}
+	return NULL;
+}
+
+static int get_id_from_port(struct virtio_serial_port *port)
+{
+	struct virtio_serial_port *match;
+	struct list_head *ptr;
+
+	list_for_each(ptr, &virtserial.port_head) {
+		match = list_entry(ptr, struct virtio_serial_port, next);
+
+		if (match == port)
+			return port->nr;
+	}
+	return VIRTIO_SERIAL_BAD_ID;
+}
+
+static struct virtio_serial_port *get_port_from_buf(char *buf)
+{
+	u32 id;
+
+	memcpy(&id, buf, sizeof(id));
+
+	return get_port_from_id(id);
+}
+
+
+static ssize_t virtserial_read(struct file *filp, char __user *ubuf,
+			       size_t count, loff_t *offp)
+{
+	struct list_head *ptr, *ptr2;
+	struct virtio_serial_port *port;
+	struct virtio_serial_port_buffer *buf;
+	ssize_t ret;
+
+	port = filp->private_data;
+
+	ret = -EINTR;
+	if (list_empty(&port->readbuf_head)) {
+		if (filp->f_flags & O_NONBLOCK)
+			return -EAGAIN;
+
+		if (wait_for_completion_interruptible(&port->have_data) < 0)
+			return ret;
+	}
+	list_for_each_safe(ptr, ptr2, &port->readbuf_head) {
+		buf = list_entry(ptr, struct virtio_serial_port_buffer, list);
+
+		/* FIXME: other buffers further in this list might
+		 * have data too
+		 */
+		if (count > buf->len - buf->offset)
+			count = buf->len - buf->offset;
+
+		ret = copy_to_user(ubuf, buf->buf + buf->offset, count);
+
+		/* Return the number of bytes actually copied */
+		ret = count - ret;
+
+		buf->offset += ret;
+
+		if (buf->len - buf->offset == 0) {
+			list_del(&buf->list);
+			kfree(buf->buf);
+			kfree(buf);
+		}
+		/* FIXME: if there's more data requested and more data
+		 * available, return it.
+		 */
+		break;
+	}
+	return ret;
+}
+
+static ssize_t virtserial_write(struct file *filp, const char __user *ubuf,
+				size_t count, loff_t *offp)
+{
+	struct virtqueue *out_vq;
+	struct virtio_serial_port *port;
+	struct virtio_serial_id id;
+	struct scatterlist sg[1];
+	char *vbuf;
+	ssize_t ret;
+	unsigned int size;
+
+	port = filp->private_data;
+
+	id.id = get_id_from_port(port);
+
+	size = min(count + sizeof(id), PAGE_SIZE);
+	vbuf = kmalloc(size, GFP_KERNEL);
+	if (!vbuf)
+		return -EFBIG;
+
+	memcpy(vbuf, &id, sizeof(id));
+	size -= sizeof(id);
+
+	ret = copy_from_user(vbuf + sizeof(id), ubuf, size);
+
+	/* Return the number of bytes actually written */
+	ret = size - ret;
+
+	out_vq = virtserial.out_vq;
+
+	sg_init_one(sg, vbuf, ret + sizeof(id));
+
+	/* add_buf wants a token to identify this buffer: we hand it any
+	 * non-NULL pointer, since there's only ever one buffer.
+	 */
+	if (out_vq->vq_ops->add_buf(out_vq, sg, 1, 0, vbuf)) {
+		/* XXX: We can't send the buffer. Report failure */
+		ret = 0;
+	}
+	/* Tell Host to go! */
+	out_vq->vq_ops->kick(out_vq);
+
+	/* FIXME: Write out the complete data in more buffers,
+	 * don't just bail out after one
+	 */
+
+	/* We're expected to return the amount of data we wrote */
+	return ret;
+}
+
+static long virtserial_ioctl(struct file *filp, unsigned int ioctl,
+			     unsigned long arg)
+{
+	struct virtio_serial_port *port;
+	struct virtio_serial_port_name *port_name;
+	struct virtio_serial_control ser_control;
+	long ret;
+
+	port = filp->private_data;
+	ser_control.port_nr = get_id_from_port(port);
+
+	ret = -EINVAL;
+	switch (ioctl) {
+	case VIRTIO_SERIAL_IOCTL_GET_PORT_NAME:
+
+		port_name = (struct virtio_serial_port_name *)arg;
+
+		if (!port->name) {
+			if (ser_control.port_nr == VIRTIO_SERIAL_BAD_ID) {
+				ret = -EINVAL;
+				break;
+			}
+			ser_control.key = VIRTIO_SERIAL_GET_PORT_NAME;
+			ret = request_control_info(&ser_control);
+			if (ret < 0) {
+				/* Of IOCTL error return codes, only
+				 * this one comes close to what has
+				 * happened: either out of memory or
+				 * the virtio-serial backend didn't
+				 * have the associated name for the
+				 * port
+				 */
+				ret = -EINVAL;
+				break;
+			}
+		}
+		ret = copy_to_user(port_name->name,
+				   port->name, VIRTIO_SERIAL_NAME_MAX_LEN);
+		if (ret < 0) {
+			ret = -EINVAL;
+			break;
+		}
+		if (ret > 0) {
+			/* Do something? There still is data to be
+			 * copied to userspace
+			 */
+			ret = 0;
+		}
+		break;
+	}
+	return ret;
+}
+
+static int virtserial_release(struct inode *inode, struct file *filp)
+{
+	pr_notice("%s\n", __func__);
+	return 0;
+}
+
+static int virtserial_open(struct inode *inode, struct file *filp)
+{
+	struct cdev *cdev = inode->i_cdev;
+	struct virtio_serial_port *port;
+
+	port = container_of(cdev, struct virtio_serial_port,
+			    cdev);
+
+	filp->private_data = port;
+	return 0;
+}
+
+static unsigned int virtserial_poll(struct file *filp, poll_table *wait)
+{
+	pr_notice("%s\n", __func__);
+	return 0;
+}
+
+static const struct file_operations virtserial_fops = {
+	.owner = THIS_MODULE,
+	.open  = virtserial_open,
+	.read  = virtserial_read,
+	.write = virtserial_write,
+	.compat_ioctl = virtserial_ioctl,
+	.unlocked_ioctl = virtserial_ioctl,
+	.poll  = virtserial_poll,
+	.release = virtserial_release,
+};
+
+static void virtio_serial_queue_work_handler(struct work_struct *work)
+{
+	struct scatterlist sg[1];
+	struct virtqueue *vq;
+	char *buf;
+
+	vq = virtserial.in_vq;
+	while (1) {
+		buf = kzalloc(PAGE_SIZE, GFP_KERNEL);
+		if (!buf)
+			break;
+
+		sg_init_one(sg, buf, PAGE_SIZE);
+
+		if (vq->vq_ops->add_buf(vq, sg, 0, 1, buf) < 0) {
+			kfree(buf);
+			break;
+		}
+	}
+	vq->vq_ops->kick(vq);
+}
+
+static void virtio_serial_rx_work_handler(struct work_struct *work)
+{
+	struct virtio_serial_port *port = NULL;
+	struct virtio_serial_port_buffer *buf;
+	struct virtqueue *vq;
+	char *tmpbuf;
+	unsigned int tmplen;
+
+	vq = virtserial.in_vq;
+	while ((tmpbuf = vq->vq_ops->get_buf(vq, &tmplen))) {
+		port = get_port_from_buf(tmpbuf);
+		if (!port) {
+			/* No valid index at start of
+			 * buffer. Drop it.
+			 */
+			pr_debug("%s: invalid index in buffer, %c %d\n",
+				 __func__, tmpbuf[0], tmpbuf[0]);
+			break;
+		}
+		buf = kzalloc(sizeof(struct virtio_serial_port_buffer),
+			      GFP_KERNEL);
+		if (!buf)
+			break;
+
+		buf->buf = tmpbuf;
+		buf->len = tmplen;
+		buf->offset = sizeof(struct virtio_serial_id);
+		list_add_tail(&buf->list, &port->readbuf_head);
+
+		complete(&port->have_data);
+	}
+	/* Allocate buffers for all the ones that got used up */
+	schedule_work(&virtserial.queue_work);
+}
+
+static void virtio_serial_tx_work_handler(struct work_struct *work)
+{
+	struct virtqueue *vq;
+	char *tmpbuf;
+	unsigned int tmplen;
+
+	vq = virtserial.out_vq;
+	while ((tmpbuf = vq->vq_ops->get_buf(vq, &tmplen)))
+		kfree(tmpbuf);
+}
+
+static void rx_intr(struct virtqueue *vq)
+{
+	schedule_work(&virtserial.rx_work);
+}
+
+static void tx_intr(struct virtqueue *vq)
+{
+	schedule_work(&virtserial.tx_work);
+}
+
+static int receive_control_response(struct virtqueue *vq)
+{
+	struct virtio_serial_port *port;
+	struct virtio_serial_control ser_control;
+	char *data;
+	unsigned int len;
+	int ret;
+
+	/* We can get spurious callbacks, e.g. shared IRQs + virtio_pci. */
+	data = vq->vq_ops->get_buf(vq, &len);
+	if (!data)
+		return 0;
+
+	/* Not enough data for the ioctl:
+	 * key + id + data
+	 */
+	/* XXX: return something else? */
+	if (len < sizeof(ser_control) + 1)
+		return -EIO;
+
+	memcpy(&ser_control, data, sizeof(ser_control));
+	len -= sizeof(ser_control);
+
+	ret = -EINVAL;
+	switch (ser_control.key) {
+	case VIRTIO_SERIAL_GET_PORT_NAME:
+		port = get_port_from_id(ser_control.port_nr);
+		if (!port) {
+			ret = -EINVAL;
+			break;
+		}
+
+		if (len > VIRTIO_SERIAL_NAME_MAX_LEN)
+			len = VIRTIO_SERIAL_NAME_MAX_LEN;
+
+		/* If the port is getting renamed */
+		kfree(port->name);
+
+		port->name = kzalloc(len, GFP_KERNEL);
+		if (!port->name) {
+			ret = -ENOMEM;
+			break;
+		}
+		memcpy(port->name, data + sizeof(ser_control), len);
+		ret = len;
+		break;
+	}
+	return ret;
+}
+
+static int request_control_info(struct virtio_serial_control *ser_control)
+{
+	struct scatterlist sg[2];
+	char *vbuf, *obuf;
+	int ret;
+
+	vbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!vbuf)
+		return -ENOMEM;
+	obuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+	if (!obuf)
+		return -ENOMEM;
+
+	memcpy(vbuf, ser_control, sizeof(struct virtio_serial_control));
+
+	sg_init_table(sg, 2);
+	sg_set_buf(&sg[0], vbuf, PAGE_SIZE);
+	sg_set_buf(&sg[1], obuf, PAGE_SIZE);
+
+	if (virtserial.ctrl_vq->vq_ops->add_buf(virtserial.ctrl_vq, sg, 1, 1,
+						obuf) == 0) {
+		/* Tell Host to go! */
+		virtserial.ctrl_vq->vq_ops->kick(virtserial.ctrl_vq);
+
+		/* Chill out until it's done with the buffer. */
+		while (!(ret = receive_control_response(virtserial.ctrl_vq)))
+			cpu_relax();
+	}
+	kfree(vbuf);
+	kfree(obuf);
+
+	return ret;
+}
+
+static int virtserial_add_port(u32 port_nr)
+{
+	struct virtio_serial_port *port;
+	int ret;
+
+	port = kzalloc(sizeof(struct virtio_serial_port), GFP_KERNEL);
+	if (!port)
+		return -ENOMEM;
+
+	port->nr = port_nr;
+
+	cdev_init(&port->cdev, &virtserial_fops);
+	port->dev = MKDEV(major, port_nr);
+
+	ret = register_chrdev_region(port->dev, 1, "virtio-serial");
+	if (ret < 0) {
+		pr_err("%s: can't register chrdev region\n", __func__);
+		goto free_cdev;
+	}
+	ret = cdev_add(&port->cdev, port->dev, 1);
+	if (ret < 0) {
+		pr_err("%s: can't add cdev\n", __func__);
+		goto free_cdev;
+	}
+	INIT_LIST_HEAD(&port->readbuf_head);
+	init_completion(&port->have_data);
+
+	list_add_tail(&port->next, &virtserial.port_head);
+
+	return 0;
+free_cdev:
+	unregister_chrdev(major, "virtio-serial");
+	return ret;
+}
+
+static int virtserial_probe(struct virtio_device *vdev)
+{
+	struct virtqueue *vqs[3];
+	struct virtio_serial_config virtsercfg;
+
+	const char *vq_names[] = { "control", "input", "output" };
+	vq_callback_t *vq_callbacks[] = { NULL, rx_intr, tx_intr };
+
+	u32 i;
+	int ret;
+
+	vdev->config->get(vdev, offsetof(struct virtio_serial_config, nr_ports),
+			  &virtsercfg.nr_ports, sizeof(virtsercfg.nr_ports));
+
+	virtserial.vdev = vdev;
+	virtserial.nr_ports = virtsercfg.nr_ports;
+
+	ret = vdev->config->find_vqs(vdev, 3, vqs, vq_callbacks, vq_names);
+	if (ret)
+		goto fail;
+
+	virtserial.ctrl_vq = vqs[0];
+	virtserial.in_vq = vqs[1];
+	virtserial.out_vq = vqs[2];
+
+	INIT_LIST_HEAD(&virtserial.port_head);
+
+	for (i = 0; i < virtserial.nr_ports; i++)
+		virtserial_add_port(i);
+
+	INIT_WORK(&virtserial.rx_work, &virtio_serial_rx_work_handler);
+	INIT_WORK(&virtserial.tx_work, &virtio_serial_tx_work_handler);
+	INIT_WORK(&virtserial.queue_work, &virtio_serial_queue_work_handler);
+
+	/* Allocate pages to fill the receive queue */
+	schedule_work(&virtserial.queue_work);
+
+	return 0;
+
+fail:
+	return ret;
+}
+
+
+static void virtserial_remove_port_data(struct virtio_serial_port *port)
+{
+	struct list_head *ptr, *ptr2;
+
+	/* Remove the buffers in which we have unconsumed data */
+	list_for_each_safe(ptr, ptr2, &port->readbuf_head) {
+		struct virtio_serial_port_buffer *buf;
+
+		buf = list_entry(ptr, struct virtio_serial_port_buffer, list);
+
+		list_del(&buf->list);
+		kfree(buf->buf);
+		kfree(buf);
+	}
+	kfree(port->name);
+}
+
+static void virtserial_remove(struct virtio_device *vdev)
+{
+	struct list_head *ptr, *ptr2;
+	char *buf;
+	int len;
+
+	unregister_chrdev(major, "virtio-serial");
+
+	cancel_work_sync(&virtserial.rx_work);
+
+	/* Free up the unused buffers in the receive queue */
+	while ((buf = virtserial.in_vq->vq_ops->get_buf(virtserial.in_vq, &len)))
+		kfree(buf);
+
+	vdev->config->del_vqs(vdev);
+
+	list_for_each_safe(ptr, ptr2, &virtserial.port_head) {
+		struct virtio_serial_port *port;
+
+		port = list_entry(ptr, struct virtio_serial_port, next);
+
+		list_del(&port->next);
+		virtserial_remove_port_data(port);
+		kfree(port);
+	}
+}
+
+static void virtserial_apply_config(struct virtio_device *vdev)
+{
+	struct virtio_serial_config virtserconf;
+
+	vdev->config->get(vdev, offsetof(struct virtio_serial_config, nr_ports),
+			  &virtserconf.nr_ports, sizeof(virtserconf.nr_ports));
+	/* FIXME: hot-add or remove ports */
+}
+
+
+static struct virtio_device_id id_table[] = {
+	{ VIRTIO_ID_SERIAL, VIRTIO_DEV_ANY_ID },
+	{ 0 },
+};
+
+static struct virtio_driver virtio_serial = {
+  //	.feature_table = features,
+  //	.feature_table_size = ARRAY_SIZE(features),
+	.driver.name =	KBUILD_MODNAME,
+	.driver.owner =	THIS_MODULE,
+	.id_table =	id_table,
+	.probe =	virtserial_probe,
+	.remove =	virtserial_remove,
+	.config_changed = virtserial_apply_config,
+};
+
+static int __init init(void)
+{
+	return register_virtio_driver(&virtio_serial);
+}
+
+static void __exit fini(void)
+{
+	unregister_virtio_driver(&virtio_serial);
+}
+module_init(init);
+module_exit(fini);
+
+MODULE_DEVICE_TABLE(virtio, id_table);
+MODULE_DESCRIPTION("Virtio serial driver");
+MODULE_LICENSE("GPL");
diff --git a/include/linux/virtio_serial.h b/include/linux/virtio_serial.h
new file mode 100644
index 0000000..3435f8b
--- /dev/null
+++ b/include/linux/virtio_serial.h
@@ -0,0 +1,42 @@
+#ifndef _LINUX_VIRTIO_SERIAL_H
+#define _LINUX_VIRTIO_SERIAL_H
+#include <linux/types.h>
+#include <linux/virtio_config.h>
+
+/* Guest kernel - Host interface */
+
+/* The ID for virtio serial */
+#define VIRTIO_ID_SERIAL		7
+#define VIRTIO_SERIAL_BAD_ID		(~(u32)0)
+
+struct virtio_serial_config {
+	__u32 nr_ports;
+	__u32 padding;
+};
+
+struct virtio_serial_control
+{
+    __u32 port_nr;
+    __u32 key;
+};
+
+/* Some defines for the control channel key */
+#define VIRTIO_SERIAL_GET_PORT_NAME	1
+
+#ifdef __KERNEL__
+
+/* Guest kernel - Guest userspace interface */
+
+/* IOCTL-related */
+#define VIRTIO_SERIAL_IO 0xAF
+
+#define VIRTIO_SERIAL_NAME_MAX_LEN	30
+struct virtio_serial_port_name {
+	char name[VIRTIO_SERIAL_NAME_MAX_LEN];
+};
+
+#define VIRTIO_SERIAL_IOCTL_GET_PORT_NAME	_IOWR(VIRTIO_SERIAL_IO, 0x00, \
+			    struct virtio_serial_port_name)
+
+#endif /* __KERNEL__ */
+#endif /* _LINUX_VIRTIO_SERIAL_H */