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

["Michael S. Tsirkin" <mst@redhat.com>]

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.


Thanks, Gregory,
I'll take a look.

>   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>
> ---
> 
>  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);

-- 
MST