Re: [PATCH] virtio: add a virtio-console to the vbus backend

[Gregory Haskins <gregory.haskins@gmail.com>]

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Michael S. Tsirkin wrote:
> On Fri, Jun 05, 2009 at 03:30:07PM -0400, Gregory Haskins wrote:
>   
>> Hi Michael,
>>   FYI: This was a patch I started to put together around the time vbus-v3 was
>>   released to demonstrate the interface for virtio devices that we needed.  I
>>   just wanted to get it out to you so you have a working example to look at
>>   what it takes to write something like virtio-net against virtio-vbus.
>>
>>   What I will do next is make a minor v3.1 release of vbus on top of kvm.git
>>   and get this patch cleaned up so we can actually run it.  Note that v3.1
>>   will just a minor port of v3 to kvm.git/HEAD, not the new iosignalfd/irqfd
>>   stuff that I have queued for v4.  Thats not ready for prime-time yet.
>>
>> ----------------------------
>>
>> virtio: add a virtio-console to the vbus backend
>>
>> A console probably doesnt need to live in the kernel since it is generally
>> not performance limited.  However, its also a very simple example, so lets
>> make a vbus backend to demonstrate the virtio interfaces.
>>
>> Signed-off-by: Gregory Haskins <ghaskins@novell.com>
>>     
>
> I'm a bit confused: does this live on the guest or host side?
>   

Host side.  The guest would run the existing virtio-console driver.

-Greg
>
>
>
>   
>> ---
>>
>>  drivers/vbus/devices/Kconfig                  |    9 
>>  drivers/vbus/devices/Makefile                 |    1 
>>  drivers/vbus/devices/virtio-console-backend.c |  461 +++++++++++++++++++++++++
>>  3 files changed, 471 insertions(+), 0 deletions(-)
>>  create mode 100644 drivers/vbus/devices/virtio-console-backend.c
>>
>> diff --git a/drivers/vbus/devices/Kconfig b/drivers/vbus/devices/Kconfig
>> index 64e4731..0239e86 100644
>> --- a/drivers/vbus/devices/Kconfig
>> +++ b/drivers/vbus/devices/Kconfig
>> @@ -15,3 +15,12 @@ config VBUS_VENETTAP
>>  
>>  	If unsure, say N
>>  
>> +config VBUS_VIRTIO_CONSOLE
>> +       tristate "Virtual-Bus Backend for virtio-console drivers"
>> +       depends on VBUS_DEVICES
>> +       select VBUS_VIRTIO_BACKEND
>> +       default n
>> +       help
>> +        Provides a virtual console device within the vbus infrastructure
>> +
>> +	If unsure, say N
>> diff --git a/drivers/vbus/devices/Makefile b/drivers/vbus/devices/Makefile
>> index 2ea7d2a..fd51cb6 100644
>> --- a/drivers/vbus/devices/Makefile
>> +++ b/drivers/vbus/devices/Makefile
>> @@ -1 +1,2 @@
>>  obj-$(CONFIG_VBUS_VENETTAP) += venet-tap.o
>> +obj-$(CONFIG_VBUS_VIRTIO_CONSOLE) += virtio-console-backend.o
>> diff --git a/drivers/vbus/devices/virtio-console-backend.c b/drivers/vbus/devices/virtio-console-backend.c
>> new file mode 100644
>> index 0000000..bf30016
>> --- /dev/null
>> +++ b/drivers/vbus/devices/virtio-console-backend.c
>> @@ -0,0 +1,461 @@
>> +/*
>> + * virtio-console for the vbus backend
>> + *
>> + * Copyright (C) 2009 Novell, Gregory Haskins <ghaskins@novell.com>
>> + *
>> + * This file is free software; you can redistribute it and/or modify
>> + * it under the terms of version 2 of the GNU General Public License
>> + * as published by the Free Software Foundation.
>> + *
>> + * 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/module.h>
>> +#include <linux/init.h>
>> +#include <linux/moduleparam.h>
>> +
>> +#include <linux/cdev.h>
>> +#include <linux/fs.h>
>> +#include <linux/major.h>
>> +
>> +#include <linux/vbus_device.h>
>> +#include <linux/virtio_vbus.h>
>> +#include <linux/virtio_console.h>
>> +
>> +MODULE_AUTHOR("Gregory Haskins");
>> +MODULE_LICENSE("GPL");
>> +
>> +#undef PDEBUG             /* undef it, just in case */
>> +#ifdef VIRTIO_CONSOLE_DEBUG
>> +#  define PDEBUG(fmt, args...) printk(KERN_DEBUG "virtio-console: " fmt, ## args)
>> +#else
>> +#  define PDEBUG(fmt, args...) /* not debugging: nothing */
>> +#endif
>> +
>> +struct _virtio_console {
>> +	spinlock_t                     lock;
>> +	char                          *name;
>> +	dev_t                          devno;
>> +	struct cdev                    cdev;
>> +	struct vbus_device             dev;
>> +	struct virtio_device_interface intf;
>> +	struct virtio_connection       conn;
>> +	struct vbus_memctx            *ctx;
>> +	struct virtqueue              *rx;
>> +	struct virtqueue              *tx;
>> +	int                            enabled:1;
>> +	int                            connected:1;
>> +	int                            opened:1;
>> +	int                            tty:1;
>> +	int                            link:1;
>> +};
>> +
>> +static struct _virtio_console *
>> +conn_to_priv(struct virtio_connection *conn)
>> +{
>> +	return container_of(conn, struct _virtio_console, conn);
>> +}
>> +
>> +static struct _virtio_console *
>> +intf_to_priv(struct virtio_device_interface *intf)
>> +{
>> +	return container_of(intf, struct _virtio_console, intf);
>> +}
>> +
>> +static struct _virtio_console *
>> +vdev_to_priv(struct vbus_device *vdev)
>> +{
>> +	return container_of(vdev, struct _virtio_console, dev);
>> +}
>> +
>> +/*
>> + * --------------------------------------------
>> + * Driver connection
>> + * --------------------------------------------
>> + */
>> +
>> +static void
>> +_virtio_console_add_vq(struct virtio_connection *vconn, int index,
>> +		       struct virtqueue *vq)
>> +{
>> +	struct _virtio_console *priv = conn_to_priv(vconn);
>> +
>> +	switch (index) {
>> +	case 0:
>> +		if (!priv->rx)
>> +			priv->rx = vq;
>> +		break;
>> +	case 1:
>> +		if (!priv->tx)
>> +			priv->tx = vq;
>> +		break;
>> +	default:
>> +		break;
>> +	}
>> +}
>> +
>> +static void
>> +_virtio_console_del_vq(struct virtio_connection *vconn, int index)
>> +{
>> +	struct _virtio_console *priv = conn_to_priv(vconn);
>> +
>> +	switch (index) {
>> +	case 0:
>> +		priv->rx = NULL;
>> +		break;
>> +	case 1:
>> +		priv->tx = NULL;
>> +		break;
>> +	default:
>> +		break;
>> +	}
>> +}
>> +
>> +static void
>> +_virtio_console_notify_vq(struct virtio_connection *vconn, int index)
>> +{
>> +
>> +}
>> +
>> +/*
>> + * This is called whenever the driver closes all references to our device
>> + */
>> +static void
>> +_virtio_console_release(struct virtio_connection *conn)
>> +{
>> +	struct _virtio_console *priv = conn_to_priv(conn);
>> +
>> +	priv->opened = false;
>> +	vbus_memctx_put(priv->ctx);
>> +}
>> +
>> +static struct virtio_connection_ops virtio_console_connection_ops = {
>> +	.add_vq            = _virtio_console_add_vq,
>> +	.del_vq            = _virtio_console_del_vq,
>> +	.notify_vq         = _virtio_console_notify_vq,
>> +	.release           = _virtio_console_release,
>> +};
>> +
>> +/*
>> + * --------------------------------------------
>> + * Interface
>> + * --------------------------------------------
>> + */
>> +
>> +/*
>> + * This is called whenever a driver wants to open our device_interface
>> + * for communication.  The connection is represented by a
>> + * virtio_connection object.  It is up to the implementation to decide
>> + * if it allows more than one connection at a time.  This simple example
>> + * does not.
>> + */
>> +static int
>> +virtio_console_intf_open(struct virtio_device_interface *intf,
>> +			 struct vbus_memctx *ctx,
>> +			 struct virtio_connection **conn)
>> +{
>> +	struct _virtio_console *priv = intf_to_priv(intf);
>> +	unsigned long flags;
>> +
>> +	PDEBUG("open\n");
>> +
>> +	spin_lock_irqsave(&priv->lock, flags);
>> +
>> +	/*
>> +	 * We only allow one connection to this device
>> +	 */
>> +	if (priv->opened) {
>> +		spin_unlock_irqrestore(&priv->lock, flags);
>> +		return -EBUSY;
>> +	}
>> +
>> +	memset(&priv->conn, 0, sizeof(priv->conn));
>> +	priv->conn.ops = &virtio_console_connection_ops;
>> +
>> +	priv->opened = true;
>> +	priv->ctx = ctx;
>> +
>> +	vbus_memctx_get(ctx);
>> +
>> +	spin_unlock_irqrestore(&priv->lock, flags);
>> +
>> +	*conn = &priv->conn;
>> +
>> +	return 0;
>> +}
>> +
>> +static void
>> +virtio_console_intf_release(struct virtio_device_interface *intf)
>> +{
>> +	kobject_put(intf->parent->dev->kobj); /* acquired on bus-connect */
>> +}
>> +
>> +static struct virtio_device_interface_ops virtio_console_intf_ops = {
>> +	.open    = virtio_console_intf_open,
>> +	.release = virtio_console_intf_release,
>> +};
>> +
>> +/*
>> + * --------------------------------------------
>> + * Bus+Device interaction
>> + * --------------------------------------------
>> + */
>> +
>> +/*
>> + * This is called whenever the admin creates a symbolic link between
>> + * a bus in /config/vbus/buses and our device.  It represents a bus
>> + * connection.  Your device can chose to allow more than one bus to
>> + * connect, or it can restrict it to one bus.  It can also choose to
>> + * register one or more device_interfaces on each bus that it
>> + * successfully connects to.
>> + *
>> + * This example device only registers a single interface
>> + */
>> +static int
>> +virtio_console_device_bus_connect(struct vbus_device *dev, struct vbus *vbus)
>> +{
>> +	struct _virtio_console *priv = vdev_to_priv(dev);
>> +	struct virtio_device_interface *intf = &priv->intf;
>> +
>> +	/* We only allow one bus to connect */
>> +	if (priv->connected)
>> +		return -EBUSY;
>> +
>> +	kobject_get(dev->kobj); /* released when we release the intf */
>> +
>> +	intf->id.vendor = 0x1af4;
>> +	intf->id.device = VIRTIO_ID_CONSOLE;
>> +
>> +	intf->ops = &virtio_console_intf_ops;
>> +
>> +	priv->connected = true;
>> +
>> +	/*
>> +	 * Our example only registers one interface.  If you need
>> +	 * more, simply call interface_register() multiple times
>> +	 */
>> +	return virtio_device_interface_register(dev, vbus, intf);
>> +}
>> +
>> +/*
>> + * This is called whenever the admin removes the symbolic link between
>> + * a bus in /config/vbus/buses and our device.
>> + */
>> +static int
>> +virtio_console_device_bus_disconnect(struct vbus_device *dev, struct vbus *vbus)
>> +{
>> +	struct _virtio_console *priv = vdev_to_priv(dev);
>> +	struct virtio_device_interface *intf = &priv->intf;
>> +
>> +	if (!priv->connected)
>> +		return -EINVAL;
>> +
>> +	virtio_device_interface_unregister(intf);
>> +
>> +	priv->connected = false;
>> +
>> +	return 0;
>> +}
>> +
>> +static void
>> +virtio_console_device_release(struct vbus_device *dev)
>> +{
>> +	struct _virtio_console *priv = vdev_to_priv(dev);
>> +
>> +	unregister_chrdev_region(priv->devno, 1);
>> +	kfree(priv);
>> +
>> +	module_put(THIS_MODULE);
>> +}
>> +
>> +
>> +static struct vbus_device_ops virtio_console_device_ops = {
>> +	.bus_connect    = virtio_console_device_bus_connect,
>> +	.bus_disconnect = virtio_console_device_bus_disconnect,
>> +	.release        = virtio_console_device_release,
>> +};
>> +
>> +#define VIRTIO_CONSOLE_TYPE "virtio-console"
>> +
>> +/*
>> + * --------------------------------------------
>> + * Character Device
>> + * --------------------------------------------
>> + */
>> +
>> +static int
>> +virtio_console_chardev_open(struct inode *inode, struct file *filp)
>> +{
>> +	struct _virtio_console *priv;
>> +
>> +	priv = container_of(inode->i_cdev, struct _virtio_console, cdev);
>> +
>> +	kobject_get(priv->dev.kobj); /* released when we release the cd */
>> +	filp->private_data = priv;
>> +
>> +	return 0;
>> +}
>> +
>> +static ssize_t
>> +virtio_console_chardev_read(struct file *filp, char __user *buf, size_t len,
>> +			    loff_t *ppos)
>> +{
>> +	struct _virtio_console *priv = filp->private_data;
>> +
>> +	return -EINVAL;
>> +}
>> +
>> +static ssize_t
>> +virtio_console_chardev_write(struct file *filp, const char __user *buf,
>> +			     size_t len, loff_t *ppos)
>> +{
>> +	struct _virtio_console *priv = filp->private_data;
>> +
>> +	return -EINVAL;
>> +}
>> +
>> +static int
>> +virtio_console_chardev_release(struct inode *inode, struct file *filp)
>> +{
>> +	struct _virtio_console *priv = filp->private_data;
>> +
>> +	kobject_put(priv->dev.kobj);
>> +
>> +	return 0;
>> +}
>> +
>> +static const struct file_operations virtio_console_chardev_ops = {
>> +	.open    = virtio_console_chardev_open,
>> +	.read    = virtio_console_chardev_read,
>> +	.write   = virtio_console_chardev_write,
>> +	.release = virtio_console_chardev_release,
>> +};
>> +
>> +/*
>> + * --------------------------------------------
>> + * Attributes
>> + * --------------------------------------------
>> + */
>> +
>> +/*
>> + * Interface attributes show up as files under
>> + * /sys/vbus/devices/$devid
>> + */
>> +
>> +static ssize_t
>> +devno_show(struct vbus_device *dev, struct vbus_device_attribute *attr,
>> +	   char *buf)
>> +{
>> +	struct _virtio_console *priv = vdev_to_priv(dev);
>> +
>> +	return snprintf(buf, PAGE_SIZE, "%d:%d\n",
>> +			MAJOR(priv->devno), MINOR(priv->devno));
>> +}
>> +
>> +static struct vbus_device_attribute attr_devno =
>> +	__ATTR_RO(devno);
>> +
>> +static struct attribute *attrs[] = {
>> +	&attr_devno.attr,
>> +	NULL,
>> +};
>> +
>> +static struct attribute_group virtio_console_attr_group = {
>> +	.attrs = attrs,
>> +};
>> +
>> +/*
>> + * --------------------------------------------
>> + * Device
>> + * --------------------------------------------
>> + */
>> +
>> +/*
>> + * This is called whenever the admin instantiates our devclass via
>> + * "mkdir /config/vbus/devices/$(inst)/virtio-console"
>> + */
>> +static int
>> +virtio_console_device_create(struct vbus_devclass *dc,
>> +			     struct vbus_device **vdev)
>> +{
>> +	struct _virtio_console *priv;
>> +	struct vbus_device *_vdev;
>> +	int ret;
>> +
>> +	priv = kzalloc(sizeof(*priv), GFP_KERNEL);
>> +	if (!priv)
>> +		return -ENOMEM;
>> +
>> +	spin_lock_init(&priv->lock);
>> +
>> +	/*
>> +	 * cdev init
>> +	 */
>> +	ret = alloc_chrdev_region(&priv->devno, TTY_MAJOR,
>> +				  1, VIRTIO_CONSOLE_TYPE);
>> +	if (ret < 0)
>> +		goto out_free;
>> +
>> +	cdev_init(&priv->cdev, &virtio_console_chardev_ops);
>> +	priv->cdev.owner = THIS_MODULE;
>> +	priv->cdev.ops = &virtio_console_chardev_ops;
>> +	ret = cdev_add(&priv->cdev, priv->devno, 1);
>> +	if (ret < 0)
>> +		goto out;
>> +
>> +	/*
>> +	 * vbus init
>> +	 */
>> +	_vdev = &priv->dev;
>> +
>> +	_vdev->type            = VIRTIO_CONSOLE_TYPE;
>> +	_vdev->ops             = &virtio_console_device_ops;
>> +	_vdev->attrs           = &virtio_console_attr_group;
>> +
>> +	*vdev = _vdev;
>> +
>> +	/*
>> +	 * We don't need a try_get because the reference is held by the
>> +	 * infrastructure during a create() operation.  This is released
>> +	 * when our device is released
>> +	 */
>> +	__module_get(THIS_MODULE);
>> +
>> +	return 0;
>> +
>> +out:
>> +	unregister_chrdev_region(priv->devno, 1);
>> +out_free:
>> +	kfree(priv);
>> +	return ret;
>> +}
>> +
>> +static struct vbus_devclass_ops virtio_console_devclass_ops = {
>> +	.create = virtio_console_device_create,
>> +};
>> +
>> +static struct vbus_devclass virtio_console_devclass = {
>> +	.name  = VIRTIO_CONSOLE_TYPE,
>> +	.ops   = &virtio_console_devclass_ops,
>> +	.owner = THIS_MODULE,
>> +};
>> +
>> +static int __init virtio_console_init(void)
>> +{
>> +	return vbus_devclass_register(&virtio_console_devclass);
>> +}
>> +
>> +static void __exit virtio_console_cleanup(void)
>> +{
>> +	vbus_devclass_unregister(&virtio_console_devclass);
>> +}
>> +
>> +module_init(virtio_console_init);
>> +module_exit(virtio_console_cleanup);
>>     
>
>   



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