Re: [Qemu-devel] [PATCH v11 01/22] vfio: Mediated device Core driver

[Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>]

* Kirti Wankhede <kwankhede@nvidia.com> [2016-11-05 02:40:35 +0530]:

Hi Kirti,

[...]
> diff --git a/drivers/vfio/Kconfig b/drivers/vfio/Kconfig
> index da6e2ce77495..23eced02aaf6 100644
> --- a/drivers/vfio/Kconfig
> +++ b/drivers/vfio/Kconfig
> @@ -48,4 +48,5 @@ menuconfig VFIO_NOIOMMU
> 
>  source "drivers/vfio/pci/Kconfig"
>  source "drivers/vfio/platform/Kconfig"
> +source "drivers/vfio/mdev/Kconfig"
>  source "virt/lib/Kconfig"
> diff --git a/drivers/vfio/Makefile b/drivers/vfio/Makefile
> index 7b8a31f63fea..4a23c13b6be4 100644
> --- a/drivers/vfio/Makefile
> +++ b/drivers/vfio/Makefile
> @@ -7,3 +7,4 @@ obj-$(CONFIG_VFIO_IOMMU_SPAPR_TCE) += vfio_iommu_spapr_tce.o
>  obj-$(CONFIG_VFIO_SPAPR_EEH) += vfio_spapr_eeh.o
>  obj-$(CONFIG_VFIO_PCI) += pci/
>  obj-$(CONFIG_VFIO_PLATFORM) += platform/
> +obj-$(CONFIG_VFIO_MDEV) += mdev/
> diff --git a/drivers/vfio/mdev/Kconfig b/drivers/vfio/mdev/Kconfig
> new file mode 100644
> index 000000000000..303c14ce2847
> --- /dev/null
> +++ b/drivers/vfio/mdev/Kconfig
> @@ -0,0 +1,10 @@
> +
> +config VFIO_MDEV
> +    tristate "Mediated device driver framework"
> +    depends on VFIO
> +    default n
> +    help
> +        Provides a framework to virtualize devices.
> +	See Documentation/vfio-mdev/vfio-mediated-device.txt for more details.
We don't have this doc at this point of time.

> +
> +        If you don't know what do here, say N.
> diff --git a/drivers/vfio/mdev/Makefile b/drivers/vfio/mdev/Makefile
> new file mode 100644
> index 000000000000..31bc04801d94
> --- /dev/null
> +++ b/drivers/vfio/mdev/Makefile
> @@ -0,0 +1,4 @@
> +
> +mdev-y := mdev_core.o mdev_sysfs.o mdev_driver.o
> +
> +obj-$(CONFIG_VFIO_MDEV) += mdev.o
> diff --git a/drivers/vfio/mdev/mdev_core.c b/drivers/vfio/mdev/mdev_core.c
> new file mode 100644
> index 000000000000..54c59f325336
> --- /dev/null
> +++ b/drivers/vfio/mdev/mdev_core.c
[...]

> +
> +/*
> + * mdev_device_remove_ops gets called from sysfs's 'remove' and when parent
> + * device is being unregistered from mdev device framework.
> + * - 'force_remove' is set to 'false' when called from sysfs's 'remove' which
> + *   indicates that if the mdev device is active, used by VMM or userspace
> + *   application, vendor driver could return error then don't remove the device.
> + * - 'force_remove' is set to 'true' when called from mdev_unregister_device()
> + *   which indicate that parent device is being removed from mdev device
> + *   framework so remove mdev device forcefully.
> + */
> +static int mdev_device_remove_ops(struct mdev_device *mdev, bool force_remove)
?
s/force_remove/force/

> +{
> +	struct parent_device *parent = mdev->parent;
> +	int ret;
> +
> +	/*
> +	 * Vendor driver can return error if VMM or userspace application is
> +	 * using this mdev device.
> +	 */
> +	ret = parent->ops->remove(mdev);
> +	if (ret && !force_remove)
> +		return -EBUSY;
> +
> +	sysfs_remove_groups(&mdev->dev.kobj, parent->ops->mdev_attr_groups);
> +	return 0;
> +}
> +
> +static int mdev_device_remove_cb(struct device *dev, void *data)
> +{
> +	if (!dev_is_mdev(dev))
> +		return 0;
> +
> +	return mdev_device_remove(dev, data ? *(bool *)data : true);
> +}
> +
> +/*
> + * mdev_register_device : Register a device
> + * @dev: device structure representing parent device.
> + * @ops: Parent device operation structure to be registered.
> + *
> + * Add device to list of registered parent devices.
> + * Returns a negative value on error, otherwise 0.
> + */
> +int mdev_register_device(struct device *dev, const struct parent_ops *ops)
> +{
> +	int ret;
> +	struct parent_device *parent;
> +
> +	/* check for mandatory ops */
> +	if (!ops || !ops->create || !ops->remove || !ops->supported_type_groups)
> +		return -EINVAL;
> +
> +	dev = get_device(dev);
> +	if (!dev)
> +		return -EINVAL;
> +
> +	mutex_lock(&parent_list_lock);
> +
> +	/* Check for duplicate */
> +	parent = __find_parent_device(dev);
> +	if (parent) {
> +		ret = -EEXIST;
> +		goto add_dev_err;
> +	}
> +
> +	parent = kzalloc(sizeof(*parent), GFP_KERNEL);
> +	if (!parent) {
> +		ret = -ENOMEM;
> +		goto add_dev_err;
> +	}
> +
> +	kref_init(&parent->ref);
> +	mutex_init(&parent->lock);
> +
> +	parent->dev = dev;
> +	parent->ops = ops;
> +
> +	if (!mdev_bus_compat_class) {
> +		mdev_bus_compat_class = class_compat_register("mdev_bus");
> +		if (!mdev_bus_compat_class) {
> +			ret = -ENOMEM;
> +			goto add_dev_err;
> +		}
> +	}
> +
> +	ret = parent_create_sysfs_files(parent);
> +	if (ret)
> +		goto add_dev_err;
> +
> +	ret = class_compat_create_link(mdev_bus_compat_class, dev, NULL);
> +	if (ret)
> +		dev_warn(dev, "Failed to create compatibility class link\n");
> +
> +	list_add(&parent->next, &parent_list);
> +	mutex_unlock(&parent_list_lock);
> +
> +	dev_info(dev, "MDEV: Registered\n");
> +	return 0;
> +
> +add_dev_err:
> +	mutex_unlock(&parent_list_lock);
> +	if (parent)
> +		mdev_put_parent(parent);
Why do this? I don't find the place that you call mdev_get_parent above.

> +	else
> +		put_device(dev);
Shouldn't we always do this?

> +	return ret;
> +}
> +EXPORT_SYMBOL(mdev_register_device);
> +
> +/*
> + * mdev_unregister_device : Unregister a parent device
> + * @dev: device structure representing parent device.
> + *
> + * Remove device from list of registered parent devices. Give a chance to free
> + * existing mediated devices for given device.
> + */
> +
> +void mdev_unregister_device(struct device *dev)
> +{
> +	struct parent_device *parent;
> +	bool force_remove = true;
> +
> +	mutex_lock(&parent_list_lock);
> +	parent = __find_parent_device(dev);
> +
> +	if (!parent) {
> +		mutex_unlock(&parent_list_lock);
> +		return;
> +	}
> +	dev_info(dev, "MDEV: Unregistering\n");
> +
> +	list_del(&parent->next);
> +	class_compat_remove_link(mdev_bus_compat_class, dev, NULL);
> +
> +	device_for_each_child(dev, (void *)&force_remove,
> +			      mdev_device_remove_cb);
> +
> +	parent_remove_sysfs_files(parent);
> +
> +	mutex_unlock(&parent_list_lock);
> +	mdev_put_parent(parent);
We also need to call put_device(dev) here since we have a get_device
during registration, no?
Or I must miss something...

> +}
> +EXPORT_SYMBOL(mdev_unregister_device);
> +
[...]

> +static int __init mdev_init(void)
> +{
> +	int ret;
> +
> +	ret = mdev_bus_register();
> +	if (ret) {
> +		pr_err("Failed to register mdev bus\n");
> +		return ret;
> +	}
> +
> +	/*
> +	 * Attempt to load known vfio_mdev.  This gives us a working environment
> +	 * without the user needing to explicitly load vfio_mdev driver.
> +	 */
> +	request_module_nowait("vfio_mdev");
We don't have this module yet.

> +
> +	return ret;
> +}
> +
> +static void __exit mdev_exit(void)
> +{
> +	if (mdev_bus_compat_class)
> +		class_compat_unregister(mdev_bus_compat_class);
> +
> +	mdev_bus_unregister();
> +}
> +
> +module_init(mdev_init)
> +module_exit(mdev_exit)
> +
> +MODULE_VERSION(DRIVER_VERSION);
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR(DRIVER_AUTHOR);
> +MODULE_DESCRIPTION(DRIVER_DESC);
> diff --git a/drivers/vfio/mdev/mdev_driver.c b/drivers/vfio/mdev/mdev_driver.c
> new file mode 100644
> index 000000000000..0b3250044a80
> --- /dev/null
> +++ b/drivers/vfio/mdev/mdev_driver.c
> @@ -0,0 +1,122 @@
> +/*
> + * MDEV driver
> + *
> + * Copyright (c) 2016, NVIDIA CORPORATION. All rights reserved.
> + *     Author: Neo Jia <cjia@nvidia.com>
> + *	       Kirti Wankhede <kwankhede@nvidia.com>
Don't know if you care much for this:
There is a TAB before your name. :>

> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/iommu.h>
> +#include <linux/mdev.h>
> +
> +#include "mdev_private.h"
> +
> +static int mdev_attach_iommu(struct mdev_device *mdev)
> +{
> +	int ret;
> +	struct iommu_group *group;
> +
> +	group = iommu_group_alloc();
> +	if (IS_ERR(group))
> +		return PTR_ERR(group);
> +
> +	ret = iommu_group_add_device(group, &mdev->dev);
> +	if (ret)
> +		goto attach_fail;
> +
> +	dev_info(&mdev->dev, "MDEV: group_id = %d\n",
> +				 iommu_group_id(group));
nit: strange indentation.
The above two lines could be safely merge into one line.

> +attach_fail:
> +	iommu_group_put(group);
> +	return ret;
> +}
> +
> +static void mdev_detach_iommu(struct mdev_device *mdev)
> +{
> +	iommu_group_remove_device(&mdev->dev);
> +	dev_info(&mdev->dev, "MDEV: detaching iommu\n");
> +}
> +
> +static int mdev_probe(struct device *dev)
> +{
> +	struct mdev_driver *drv = to_mdev_driver(dev->driver);
> +	struct mdev_device *mdev = to_mdev_device(dev);
> +	int ret;
> +
> +	ret = mdev_attach_iommu(mdev);
> +	if (ret)
> +		return ret;
> +
> +	if (drv && drv->probe)
> +		ret = drv->probe(dev);
> +
> +	if (ret)
> +		mdev_detach_iommu(mdev);
?
	if (drv && drv->probe) {
		ret = drv->probe(dev);
		if (ret)
			mdev_detach_iommu(mdev);
	}

> +
> +	return ret;
> +}
> +
> +static int mdev_remove(struct device *dev)
> +{
> +	struct mdev_driver *drv = to_mdev_driver(dev->driver);
> +	struct mdev_device *mdev = to_mdev_device(dev);
> +
> +	if (drv && drv->remove)
> +		drv->remove(dev);
> +
> +	mdev_detach_iommu(mdev);
> +
> +	return 0;
> +}
> +
> +struct bus_type mdev_bus_type = {
> +	.name		= "mdev",
> +	.probe		= mdev_probe,
> +	.remove		= mdev_remove,
> +};
> +EXPORT_SYMBOL_GPL(mdev_bus_type);
> +
> +/*
Is this a kernel-doc comment?
It should be started with:
/**

> + * mdev_register_driver - register a new MDEV driver
> + * @drv: the driver to register
> + * @owner: module owner of driver to be registered
> + *
> + * Returns a negative value on error, otherwise 0.
> + */
> +int mdev_register_driver(struct mdev_driver *drv, struct module *owner)
> +{
> +	/* initialize common driver fields */
> +	drv->driver.name = drv->name;
> +	drv->driver.bus = &mdev_bus_type;
> +	drv->driver.owner = owner;
> +
> +	/* register with core */
> +	return driver_register(&drv->driver);
> +}
> +EXPORT_SYMBOL(mdev_register_driver);
> +
> +/*
> + * mdev_unregister_driver - unregister MDEV driver
> + * @drv: the driver to unregister
> + *
Empty line.

> + */
> +void mdev_unregister_driver(struct mdev_driver *drv)
> +{
> +	driver_unregister(&drv->driver);
> +}
> +EXPORT_SYMBOL(mdev_unregister_driver);
> +
> +int mdev_bus_register(void)
> +{
> +	return bus_register(&mdev_bus_type);
> +}
> +
> +void mdev_bus_unregister(void)
> +{
> +	bus_unregister(&mdev_bus_type);
> +}
[...]

> diff --git a/include/linux/mdev.h b/include/linux/mdev.h
> +/* Mediated device */
> +struct mdev_device {
> +	struct device		dev;
> +	struct parent_device	*parent;
> +	uuid_le			uuid;
> +	void			*driver_data;
> +
> +	/* internal */
> +	struct kref		ref;
> +	struct list_head	next;
> +	struct kobject		*type_kobj;
> +};
> +
> +
Empty line.

> +/**
> + * struct parent_ops - Structure to be registered for each parent device to
> + * register the device to mdev module.
> + *
[...]

> + * @mmap:		mmap callback
No need a piece of description for arguments of the mmap callback?

> + * Parent device that support mediated device should be registered with mdev
> + * module with parent_ops structure.
> + **/
> +
> +struct parent_ops {
> +	struct module   *owner;
> +	const struct attribute_group **dev_attr_groups;
> +	const struct attribute_group **mdev_attr_groups;
> +	struct attribute_group **supported_type_groups;
> +
> +	int     (*create)(struct kobject *kobj, struct mdev_device *mdev);
> +	int     (*remove)(struct mdev_device *mdev);
> +	int     (*open)(struct mdev_device *mdev);
> +	void    (*release)(struct mdev_device *mdev);
> +	ssize_t (*read)(struct mdev_device *mdev, char __user *buf,
> +			size_t count, loff_t *ppos);
> +	ssize_t (*write)(struct mdev_device *mdev, const char __user *buf,
> +			 size_t count, loff_t *ppos);
> +	ssize_t (*ioctl)(struct mdev_device *mdev, unsigned int cmd,
> +			 unsigned long arg);
> +	int	(*mmap)(struct mdev_device *mdev, struct vm_area_struct *vma);
> +};
> +
[...]

-- 
Dong Jia