drivers/vfio/container.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2012 Red Hat, Inc.  All rights reserved.
 *
 * VFIO container (/dev/vfio/vfio)
 */
#include <linux/file.h>
#include <linux/slab.h>
#include <linux/fs.h>
#include <linux/capability.h>
#include <linux/iommu.h>
#include <linux/miscdevice.h>
#include <linux/vfio.h>
#include <uapi/linux/vfio.h>

#include "vfio.h"

struct vfio_container {
	struct kref			kref;
	struct list_head		group_list;
	struct rw_semaphore		group_lock;
	struct vfio_iommu_driver	*iommu_driver;
	void				*iommu_data;
	bool				noiommu;
};

static struct vfio {
	struct list_head		iommu_drivers_list;
	struct mutex			iommu_drivers_lock;
} vfio;

static void *vfio_noiommu_open(unsigned long arg)
{
	if (arg != VFIO_NOIOMMU_IOMMU)
		return ERR_PTR(-EINVAL);
	if (!capable(CAP_SYS_RAWIO))
		return ERR_PTR(-EPERM);

	return NULL;
}

static void vfio_noiommu_release(void *iommu_data)
{
}

static long vfio_noiommu_ioctl(void *iommu_data,
			       unsigned int cmd, unsigned long arg)
{
	if (cmd == VFIO_CHECK_EXTENSION)
		return vfio_noiommu && (arg == VFIO_NOIOMMU_IOMMU) ? 1 : 0;

	return -ENOTTY;
}

static int vfio_noiommu_attach_group(void *iommu_data,
		struct iommu_group *iommu_group, enum vfio_group_type type)
{
	return 0;
}

static void vfio_noiommu_detach_group(void *iommu_data,
				      struct iommu_group *iommu_group)
{
}

static const struct vfio_iommu_driver_ops vfio_noiommu_ops = {
	.name = "vfio-noiommu",
	.owner = THIS_MODULE,
	.open = vfio_noiommu_open,
	.release = vfio_noiommu_release,
	.ioctl = vfio_noiommu_ioctl,
	.attach_group = vfio_noiommu_attach_group,
	.detach_group = vfio_noiommu_detach_group,
};

/*
 * Only noiommu containers can use vfio-noiommu and noiommu containers can only
 * use vfio-noiommu.
 */
static bool vfio_iommu_driver_allowed(struct vfio_container *container,
				      const struct vfio_iommu_driver *driver)
{
	if (!IS_ENABLED(CONFIG_VFIO_NOIOMMU))
		return true;
	return container->noiommu == (driver->ops == &vfio_noiommu_ops);
}

/*
 * IOMMU driver registration
 */
int vfio_register_iommu_driver(const struct vfio_iommu_driver_ops *ops)
{
	struct vfio_iommu_driver *driver, *tmp;

	if (WARN_ON(!ops->register_device != !ops->unregister_device))
		return -EINVAL;

	driver = kzalloc(sizeof(*driver), GFP_KERNEL);
	if (!driver)
		return -ENOMEM;

	driver->ops = ops;

	mutex_lock(&vfio.iommu_drivers_lock);

	/* Check for duplicates */
	list_for_each_entry(tmp, &vfio.iommu_drivers_list, vfio_next) {
		if (tmp->ops == ops) {
			mutex_unlock(&vfio.iommu_drivers_lock);
			kfree(driver);
			return -EINVAL;
		}
	}

	list_add(&driver->vfio_next, &vfio.iommu_drivers_list);

	mutex_unlock(&vfio.iommu_drivers_lock);

	return 0;
}
EXPORT_SYMBOL_GPL(vfio_register_iommu_driver);

void vfio_unregister_iommu_driver(const struct vfio_iommu_driver_ops *ops)
{
	struct vfio_iommu_driver *driver;

	mutex_lock(&vfio.iommu_drivers_lock);
	list_for_each_entry(driver, &vfio.iommu_drivers_list, vfio_next) {
		if (driver->ops == ops) {
			list_del(&driver->vfio_next);
			mutex_unlock(&vfio.iommu_drivers_lock);
			kfree(driver);
			return;
		}
	}
	mutex_unlock(&vfio.iommu_drivers_lock);
}
EXPORT_SYMBOL_GPL(vfio_unregister_iommu_driver);

/*
 * Container objects - containers are created when /dev/vfio/vfio is
 * opened, but their lifecycle extends until the last user is done, so
 * it's freed via kref.  Must support container/group/device being
 * closed in any order.
 */
static void vfio_container_release(struct kref *kref)
{
	struct vfio_container *container;
	container = container_of(kref, struct vfio_container, kref);

	kfree(container);
}

static void vfio_container_get(struct vfio_container *container)
{
	kref_get(&container->kref);
}

static void vfio_container_put(struct vfio_container *container)
{
	kref_put(&container->kref, vfio_container_release);
}

void vfio_device_container_register(struct vfio_device *device)
{
	struct vfio_iommu_driver *iommu_driver =
		device->group->container->iommu_driver;

	if (iommu_driver && iommu_driver->ops->register_device)
		iommu_driver->ops->register_device(
			device->group->container->iommu_data, device);
}

void vfio_device_container_unregister(struct vfio_device *device)
{
	struct vfio_iommu_driver *iommu_driver =
		device->group->container->iommu_driver;

	if (iommu_driver && iommu_driver->ops->unregister_device)
		iommu_driver->ops->unregister_device(
			device->group->container->iommu_data, device);
}

static long
vfio_container_ioctl_check_extension(struct vfio_container *container,
				     unsigned long arg)
{
	struct vfio_iommu_driver *driver;
	long ret = 0;

	down_read(&container->group_lock);

	driver = container->iommu_driver;

	switch (arg) {
		/* No base extensions yet */
	default:
		/*
		 * If no driver is set, poll all registered drivers for
		 * extensions and return the first positive result.  If
		 * a driver is already set, further queries will be passed
		 * only to that driver.
		 */
		if (!driver) {
			mutex_lock(&vfio.iommu_drivers_lock);
			list_for_each_entry(driver, &vfio.iommu_drivers_list,
					    vfio_next) {

				if (!list_empty(&container->group_list) &&
				    !vfio_iommu_driver_allowed(container,
							       driver))
					continue;
				if (!try_module_get(driver->ops->owner))
					continue;

				ret = driver->ops->ioctl(NULL,
							 VFIO_CHECK_EXTENSION,
							 arg);
				module_put(driver->ops->owner);
				if (ret > 0)
					break;
			}
			mutex_unlock(&vfio.iommu_drivers_lock);
		} else
			ret = driver->ops->ioctl(container->iommu_data,
						 VFIO_CHECK_EXTENSION, arg);
	}

	up_read(&container->group_lock);

	return ret;
}

/* hold write lock on container->group_lock */
static int __vfio_container_attach_groups(struct vfio_container *container,
					  struct vfio_iommu_driver *driver,
					  void *data)
{
	struct vfio_group *group;
	int ret = -ENODEV;

	list_for_each_entry(group, &container->group_list, container_next) {
		ret = driver->ops->attach_group(data, group->iommu_group,
						group->type);
		if (ret)
			goto unwind;
	}

	return ret;

unwind:
	list_for_each_entry_continue_reverse(group, &container->group_list,
					     container_next) {
		driver->ops->detach_group(data, group->iommu_group);
	}

	return ret;
}

static long vfio_ioctl_set_iommu(struct vfio_container *container,
				 unsigned long arg)
{
	struct vfio_iommu_driver *driver;
	long ret = -ENODEV;

	down_write(&container->group_lock);

	/*
	 * The container is designed to be an unprivileged interface while
	 * the group can be assigned to specific users.  Therefore, only by
	 * adding a group to a container does the user get the privilege of
	 * enabling the iommu, which may allocate finite resources.  There
	 * is no unset_iommu, but by removing all the groups from a container,
	 * the container is deprivileged and returns to an unset state.
	 */
	if (list_empty(&container->group_list) || container->iommu_driver) {
		up_write(&container->group_lock);
		return -EINVAL;
	}

	mutex_lock(&vfio.iommu_drivers_lock);
	list_for_each_entry(driver, &vfio.iommu_drivers_list, vfio_next) {
		void *data;

		if (!vfio_iommu_driver_allowed(container, driver))
			continue;
		if (!try_module_get(driver->ops->owner))
			continue;

		/*
		 * The arg magic for SET_IOMMU is the same as CHECK_EXTENSION,
		 * so test which iommu driver reported support for this
		 * extension and call open on them.  We also pass them the
		 * magic, allowing a single driver to support multiple
		 * interfaces if they'd like.
		 */
		if (driver->ops->ioctl(NULL, VFIO_CHECK_EXTENSION, arg) <= 0) {
			module_put(driver->ops->owner);
			continue;
		}

		data = driver->ops->open(arg);
		if (IS_ERR(data)) {
			ret = PTR_ERR(data);
			module_put(driver->ops->owner);
			continue;
		}

		ret = __vfio_container_attach_groups(container, driver, data);
		if (ret) {
			driver->ops->release(data);
			module_put(driver->ops->owner);
			continue;
		}

		container->iommu_driver = driver;
		container->iommu_data = data;
		break;
	}

	mutex_unlock(&vfio.iommu_drivers_lock);
	up_write(&container->group_lock);

	return ret;
}

static long vfio_fops_unl_ioctl(struct file *filep,
				unsigned int cmd, unsigned long arg)
{
	struct vfio_container *container = filep->private_data;
	struct vfio_iommu_driver *driver;
	void *data;
	long ret = -EINVAL;

	if (!container)
		return ret;

	switch (cmd) {
	case VFIO_GET_API_VERSION:
		ret = VFIO_API_VERSION;
		break;
	case VFIO_CHECK_EXTENSION:
		ret = vfio_container_ioctl_check_extension(container, arg);
		break;
	case VFIO_SET_IOMMU:
		ret = vfio_ioctl_set_iommu(container, arg);
		break;
	default:
		driver = container->iommu_driver;
		data = container->iommu_data;

		if (driver) /* passthrough all unrecognized ioctls */
			ret = driver->ops->ioctl(data, cmd, arg);
	}

	return ret;
}

static int vfio_fops_open(struct inode *inode, struct file *filep)
{
	struct vfio_container *container;

	container = kzalloc(sizeof(*container), GFP_KERNEL_ACCOUNT);
	if (!container)
		return -ENOMEM;

	INIT_LIST_HEAD(&container->group_list);
	init_rwsem(&container->group_lock);
	kref_init(&container->kref);

	filep->private_data = container;

	return 0;
}

static int vfio_fops_release(struct inode *inode, struct file *filep)
{
	struct vfio_container *container = filep->private_data;

	filep->private_data = NULL;

	vfio_container_put(container);

	return 0;
}

static const struct file_operations vfio_fops = {
	.owner		= THIS_MODULE,
	.open		= vfio_fops_open,
	.release	= vfio_fops_release,
	.unlocked_ioctl	= vfio_fops_unl_ioctl,
	.compat_ioctl	= compat_ptr_ioctl,
};

struct vfio_container *vfio_container_from_file(struct file *file)
{
	struct vfio_container *container;

	/* Sanity check, is this really our fd? */
	if (file->f_op != &vfio_fops)
		return NULL;

	container = file->private_data;
	WARN_ON(!container); /* fget ensures we don't race vfio_release */
	return container;
}

static struct miscdevice vfio_dev = {
	.minor = VFIO_MINOR,
	.name = "vfio",
	.fops = &vfio_fops,
	.nodename = "vfio/vfio",
	.mode = S_IRUGO | S_IWUGO,
};

int vfio_container_attach_group(struct vfio_container *container,
				struct vfio_group *group)
{
	struct vfio_iommu_driver *driver;
	int ret = 0;

	lockdep_assert_held(&group->group_lock);

	if (group->type == VFIO_NO_IOMMU && !capable(CAP_SYS_RAWIO))
		return -EPERM;

	down_write(&container->group_lock);

	/* Real groups and fake groups cannot mix */
	if (!list_empty(&container->group_list) &&
	    container->noiommu != (group->type == VFIO_NO_IOMMU)) {
		ret = -EPERM;
		goto out_unlock_container;
	}

	if (group->type == VFIO_IOMMU) {
		ret = iommu_group_claim_dma_owner(group->iommu_group, group);
		if (ret)
			goto out_unlock_container;
	}

	driver = container->iommu_driver;
	if (driver) {
		ret = driver->ops->attach_group(container->iommu_data,
						group->iommu_group,
						group->type);
		if (ret) {
			if (group->type == VFIO_IOMMU)
				iommu_group_release_dma_owner(
					group->iommu_group);
			goto out_unlock_container;
		}
	}

	group->container = container;
	group->container_users = 1;
	container->noiommu = (group->type == VFIO_NO_IOMMU);
	list_add(&group->container_next, &container->group_list);

	/* Get a reference on the container and mark a user within the group */
	vfio_container_get(container);

out_unlock_container:
	up_write(&container->group_lock);
	return ret;
}

void vfio_group_detach_container(struct vfio_group *group)
{
	struct vfio_container *container = group->container;
	struct vfio_iommu_driver *driver;

	lockdep_assert_held(&group->group_lock);
	WARN_ON(group->container_users != 1);

	down_write(&container->group_lock);

	driver = container->iommu_driver;
	if (driver)
		driver->ops->detach_group(container->iommu_data,
					  group->iommu_group);

	if (group->type == VFIO_IOMMU)
		iommu_group_release_dma_owner(group->iommu_group);

	group->container = NULL;
	group->container_users = 0;
	list_del(&group->container_next);

	/* Detaching the last group deprivileges a container, remove iommu */
	if (driver && list_empty(&container->group_list)) {
		driver->ops->release(container->iommu_data);
		module_put(driver->ops->owner);
		container->iommu_driver = NULL;
		container->iommu_data = NULL;
	}

	up_write(&container->group_lock);

	vfio_container_put(container);
}

int vfio_group_use_container(struct vfio_group *group)
{
	lockdep_assert_held(&group->group_lock);

	/*
	 * The container fd has been assigned with VFIO_GROUP_SET_CONTAINER but
	 * VFIO_SET_IOMMU hasn't been done yet.
	 */
	if (!group->container->iommu_driver)
		return -EINVAL;

	if (group->type == VFIO_NO_IOMMU && !capable(CAP_SYS_RAWIO))
		return -EPERM;

	get_file(group->opened_file);
	group->container_users++;
	return 0;
}

void vfio_group_unuse_container(struct vfio_group *group)
{
	lockdep_assert_held(&group->group_lock);

	WARN_ON(group->container_users <= 1);
	group->container_users--;
	fput(group->opened_file);
}

int vfio_device_container_pin_pages(struct vfio_device *device,
				    dma_addr_t iova, int npage,
				    int prot, struct page **pages)
{
	struct vfio_container *container = device->group->container;
	struct iommu_group *iommu_group = device->group->iommu_group;
	struct vfio_iommu_driver *driver = container->iommu_driver;

	if (npage > VFIO_PIN_PAGES_MAX_ENTRIES)
		return -E2BIG;

	if (unlikely(!driver || !driver->ops->pin_pages))
		return -ENOTTY;
	return driver->ops->pin_pages(container->iommu_data, iommu_group, iova,
				      npage, prot, pages);
}

void vfio_device_container_unpin_pages(struct vfio_device *device,
				       dma_addr_t iova, int npage)
{
	struct vfio_container *container = device->group->container;

	if (WARN_ON(npage <= 0 || npage > VFIO_PIN_PAGES_MAX_ENTRIES))
		return;

	container->iommu_driver->ops->unpin_pages(container->iommu_data, iova,
						  npage);
}

int vfio_device_container_dma_rw(struct vfio_device *device,
				 dma_addr_t iova, void *data,
				 size_t len, bool write)
{
	struct vfio_container *container = device->group->container;
	struct vfio_iommu_driver *driver = container->iommu_driver;

	if (unlikely(!driver || !driver->ops->dma_rw))
		return -ENOTTY;
	return driver->ops->dma_rw(container->iommu_data, iova, data, len,
				   write);
}

int __init vfio_container_init(void)
{
	int ret;

	mutex_init(&vfio.iommu_drivers_lock);
	INIT_LIST_HEAD(&vfio.iommu_drivers_list);

	ret = misc_register(&vfio_dev);
	if (ret) {
		pr_err("vfio: misc device register failed\n");
		return ret;
	}

	if (IS_ENABLED(CONFIG_VFIO_NOIOMMU)) {
		ret = vfio_register_iommu_driver(&vfio_noiommu_ops);
		if (ret)
			goto err_misc;
	}
	return 0;

err_misc:
	misc_deregister(&vfio_dev);
	return ret;
}

void vfio_container_cleanup(void)
{
	if (IS_ENABLED(CONFIG_VFIO_NOIOMMU))
		vfio_unregister_iommu_driver(&vfio_noiommu_ops);
	misc_deregister(&vfio_dev);
	mutex_destroy(&vfio.iommu_drivers_lock);
}

MODULE_ALIAS_MISCDEV(VFIO_MINOR);
MODULE_ALIAS("devname:vfio/vfio");