1 files changed, 1509 insertions, 0 deletions

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
new file mode 100644
index 00000000000..f018d8d0f97
--- /dev/null
+++ b/drivers/vfio/vfio.c
@@ -0,0 +1,1509 @@
+/*
+ * VFIO core
+ *
+ * Copyright (C) 2012 Red Hat, Inc.  All rights reserved.
+ *     Author: Alex Williamson <alex.williamson@redhat.com>
+ *
+ * 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.
+ *
+ * Derived from original vfio:
+ * Copyright 2010 Cisco Systems, Inc.  All rights reserved.
+ * Author: Tom Lyon, pugs@cisco.com
+ */
+
+#include <linux/cdev.h>
+#include <linux/compat.h>
+#include <linux/device.h>
+#include <linux/file.h>
+#include <linux/anon_inodes.h>
+#include <linux/fs.h>
+#include <linux/idr.h>
+#include <linux/iommu.h>
+#include <linux/list.h>
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/rwsem.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/stat.h>
+#include <linux/string.h>
+#include <linux/uaccess.h>
+#include <linux/vfio.h>
+#include <linux/wait.h>
+
+#define DRIVER_VERSION	"0.3"
+#define DRIVER_AUTHOR	"Alex Williamson <alex.williamson@redhat.com>"
+#define DRIVER_DESC	"VFIO - User Level meta-driver"
+
+static struct vfio {
+	struct class			*class;
+	struct list_head		iommu_drivers_list;
+	struct mutex			iommu_drivers_lock;
+	struct list_head		group_list;
+	struct idr			group_idr;
+	struct mutex			group_lock;
+	struct cdev			group_cdev;
+	dev_t				group_devt;
+	wait_queue_head_t		release_q;
+} vfio;
+
+struct vfio_iommu_driver {
+	const struct vfio_iommu_driver_ops	*ops;
+	struct list_head			vfio_next;
+};
+
+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;
+};
+
+struct vfio_group {
+	struct kref			kref;
+	int				minor;
+	atomic_t			container_users;
+	struct iommu_group		*iommu_group;
+	struct vfio_container		*container;
+	struct list_head		device_list;
+	struct mutex			device_lock;
+	struct device			*dev;
+	struct notifier_block		nb;
+	struct list_head		vfio_next;
+	struct list_head		container_next;
+	atomic_t			opened;
+};
+
+struct vfio_device {
+	struct kref			kref;
+	struct device			*dev;
+	const struct vfio_device_ops	*ops;
+	struct vfio_group		*group;
+	struct list_head		group_next;
+	void				*device_data;
+};
+
+/**
+ * IOMMU driver registration
+ */
+int vfio_register_iommu_driver(const struct vfio_iommu_driver_ops *ops)
+{
+	struct vfio_iommu_driver *driver, *tmp;
+
+	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);
+
+/**
+ * Group minor allocation/free - both called with vfio.group_lock held
+ */
+static int vfio_alloc_group_minor(struct vfio_group *group)
+{
+	return idr_alloc(&vfio.group_idr, group, 0, MINORMASK + 1, GFP_KERNEL);
+}
+
+static void vfio_free_group_minor(int minor)
+{
+	idr_remove(&vfio.group_idr, minor);
+}
+
+static int vfio_iommu_group_notifier(struct notifier_block *nb,
+				     unsigned long action, void *data);
+static void vfio_group_get(struct vfio_group *group);
+
+/**
+ * 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_get(struct vfio_container *container)
+{
+	kref_get(&container->kref);
+}
+
+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_put(struct vfio_container *container)
+{
+	kref_put(&container->kref, vfio_container_release);
+}
+
+static void vfio_group_unlock_and_free(struct vfio_group *group)
+{
+	mutex_unlock(&vfio.group_lock);
+	/*
+	 * Unregister outside of lock.  A spurious callback is harmless now
+	 * that the group is no longer in vfio.group_list.
+	 */
+	iommu_group_unregister_notifier(group->iommu_group, &group->nb);
+	kfree(group);
+}
+
+/**
+ * Group objects - create, release, get, put, search
+ */
+static struct vfio_group *vfio_create_group(struct iommu_group *iommu_group)
+{
+	struct vfio_group *group, *tmp;
+	struct device *dev;
+	int ret, minor;
+
+	group = kzalloc(sizeof(*group), GFP_KERNEL);
+	if (!group)
+		return ERR_PTR(-ENOMEM);
+
+	kref_init(&group->kref);
+	INIT_LIST_HEAD(&group->device_list);
+	mutex_init(&group->device_lock);
+	atomic_set(&group->container_users, 0);
+	atomic_set(&group->opened, 0);
+	group->iommu_group = iommu_group;
+
+	group->nb.notifier_call = vfio_iommu_group_notifier;
+
+	/*
+	 * blocking notifiers acquire a rwsem around registering and hold
+	 * it around callback.  Therefore, need to register outside of
+	 * vfio.group_lock to avoid A-B/B-A contention.  Our callback won't
+	 * do anything unless it can find the group in vfio.group_list, so
+	 * no harm in registering early.
+	 */
+	ret = iommu_group_register_notifier(iommu_group, &group->nb);
+	if (ret) {
+		kfree(group);
+		return ERR_PTR(ret);
+	}
+
+	mutex_lock(&vfio.group_lock);
+
+	minor = vfio_alloc_group_minor(group);
+	if (minor < 0) {
+		vfio_group_unlock_and_free(group);
+		return ERR_PTR(minor);
+	}
+
+	/* Did we race creating this group? */
+	list_for_each_entry(tmp, &vfio.group_list, vfio_next) {
+		if (tmp->iommu_group == iommu_group) {
+			vfio_group_get(tmp);
+			vfio_free_group_minor(minor);
+			vfio_group_unlock_and_free(group);
+			return tmp;
+		}
+	}
+
+	dev = device_create(vfio.class, NULL,
+			    MKDEV(MAJOR(vfio.group_devt), minor),
+			    group, "%d", iommu_group_id(iommu_group));
+	if (IS_ERR(dev)) {
+		vfio_free_group_minor(minor);
+		vfio_group_unlock_and_free(group);
+		return (struct vfio_group *)dev; /* ERR_PTR */
+	}
+
+	group->minor = minor;
+	group->dev = dev;
+
+	list_add(&group->vfio_next, &vfio.group_list);
+
+	mutex_unlock(&vfio.group_lock);
+
+	return group;
+}
+
+/* called with vfio.group_lock held */
+static void vfio_group_release(struct kref *kref)
+{
+	struct vfio_group *group = container_of(kref, struct vfio_group, kref);
+
+	WARN_ON(!list_empty(&group->device_list));
+
+	device_destroy(vfio.class, MKDEV(MAJOR(vfio.group_devt), group->minor));
+	list_del(&group->vfio_next);
+	vfio_free_group_minor(group->minor);
+	vfio_group_unlock_and_free(group);
+}
+
+static void vfio_group_put(struct vfio_group *group)
+{
+	kref_put_mutex(&group->kref, vfio_group_release, &vfio.group_lock);
+}
+
+/* Assume group_lock or group reference is held */
+static void vfio_group_get(struct vfio_group *group)
+{
+	kref_get(&group->kref);
+}
+
+/*
+ * Not really a try as we will sleep for mutex, but we need to make
+ * sure the group pointer is valid under lock and get a reference.
+ */
+static struct vfio_group *vfio_group_try_get(struct vfio_group *group)
+{
+	struct vfio_group *target = group;
+
+	mutex_lock(&vfio.group_lock);
+	list_for_each_entry(group, &vfio.group_list, vfio_next) {
+		if (group == target) {
+			vfio_group_get(group);
+			mutex_unlock(&vfio.group_lock);
+			return group;
+		}
+	}
+	mutex_unlock(&vfio.group_lock);
+
+	return NULL;
+}
+
+static
+struct vfio_group *vfio_group_get_from_iommu(struct iommu_group *iommu_group)
+{
+	struct vfio_group *group;
+
+	mutex_lock(&vfio.group_lock);
+	list_for_each_entry(group, &vfio.group_list, vfio_next) {
+		if (group->iommu_group == iommu_group) {
+			vfio_group_get(group);
+			mutex_unlock(&vfio.group_lock);
+			return group;
+		}
+	}
+	mutex_unlock(&vfio.group_lock);
+
+	return NULL;
+}
+
+static struct vfio_group *vfio_group_get_from_minor(int minor)
+{
+	struct vfio_group *group;
+
+	mutex_lock(&vfio.group_lock);
+	group = idr_find(&vfio.group_idr, minor);
+	if (!group) {
+		mutex_unlock(&vfio.group_lock);
+		return NULL;
+	}
+	vfio_group_get(group);
+	mutex_unlock(&vfio.group_lock);
+
+	return group;
+}
+
+/**
+ * Device objects - create, release, get, put, search
+ */
+static
+struct vfio_device *vfio_group_create_device(struct vfio_group *group,
+					     struct device *dev,
+					     const struct vfio_device_ops *ops,
+					     void *device_data)
+{
+	struct vfio_device *device;
+
+	device = kzalloc(sizeof(*device), GFP_KERNEL);
+	if (!device)
+		return ERR_PTR(-ENOMEM);
+
+	kref_init(&device->kref);
+	device->dev = dev;
+	device->group = group;
+	device->ops = ops;
+	device->device_data = device_data;
+	dev_set_drvdata(dev, device);
+
+	/* No need to get group_lock, caller has group reference */
+	vfio_group_get(group);
+
+	mutex_lock(&group->device_lock);
+	list_add(&device->group_next, &group->device_list);
+	mutex_unlock(&group->device_lock);
+
+	return device;
+}
+
+static void vfio_device_release(struct kref *kref)
+{
+	struct vfio_device *device = container_of(kref,
+						  struct vfio_device, kref);
+	struct vfio_group *group = device->group;
+
+	list_del(&device->group_next);
+	mutex_unlock(&group->device_lock);
+
+	dev_set_drvdata(device->dev, NULL);
+
+	kfree(device);
+
+	/* vfio_del_group_dev may be waiting for this device */
+	wake_up(&vfio.release_q);
+}
+
+/* Device reference always implies a group reference */
+void vfio_device_put(struct vfio_device *device)
+{
+	struct vfio_group *group = device->group;
+	kref_put_mutex(&device->kref, vfio_device_release, &group->device_lock);
+	vfio_group_put(group);
+}
+EXPORT_SYMBOL_GPL(vfio_device_put);
+
+static void vfio_device_get(struct vfio_device *device)
+{
+	vfio_group_get(device->group);
+	kref_get(&device->kref);
+}
+
+static struct vfio_device *vfio_group_get_device(struct vfio_group *group,
+						 struct device *dev)
+{
+	struct vfio_device *device;
+
+	mutex_lock(&group->device_lock);
+	list_for_each_entry(device, &group->device_list, group_next) {
+		if (device->dev == dev) {
+			vfio_device_get(device);
+			mutex_unlock(&group->device_lock);
+			return device;
+		}
+	}
+	mutex_unlock(&group->device_lock);
+	return NULL;
+}
+
+/*
+ * Whitelist some drivers that we know are safe (no dma) or just sit on
+ * a device.  It's not always practical to leave a device within a group
+ * driverless as it could get re-bound to something unsafe.
+ */
+static const char * const vfio_driver_whitelist[] = { "pci-stub", "pcieport" };
+
+static bool vfio_whitelisted_driver(struct device_driver *drv)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(vfio_driver_whitelist); i++) {
+		if (!strcmp(drv->name, vfio_driver_whitelist[i]))
+			return true;
+	}
+
+	return false;
+}
+
+/*
+ * A vfio group is viable for use by userspace if all devices are either
+ * driver-less or bound to a vfio or whitelisted driver.  We test the
+ * latter by the existence of a struct vfio_device matching the dev.
+ */
+static int vfio_dev_viable(struct device *dev, void *data)
+{
+	struct vfio_group *group = data;
+	struct vfio_device *device;
+	struct device_driver *drv = ACCESS_ONCE(dev->driver);
+
+	if (!drv || vfio_whitelisted_driver(drv))
+		return 0;
+
+	device = vfio_group_get_device(group, dev);
+	if (device) {
+		vfio_device_put(device);
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
+/**
+ * Async device support
+ */
+static int vfio_group_nb_add_dev(struct vfio_group *group, struct device *dev)
+{
+	struct vfio_device *device;
+
+	/* Do we already know about it?  We shouldn't */
+	device = vfio_group_get_device(group, dev);
+	if (WARN_ON_ONCE(device)) {
+		vfio_device_put(device);
+		return 0;
+	}
+
+	/* Nothing to do for idle groups */
+	if (!atomic_read(&group->container_users))
+		return 0;
+
+	/* TODO Prevent device auto probing */
+	WARN("Device %s added to live group %d!\n", dev_name(dev),
+	     iommu_group_id(group->iommu_group));
+
+	return 0;
+}
+
+static int vfio_group_nb_verify(struct vfio_group *group, struct device *dev)
+{
+	/* We don't care what happens when the group isn't in use */
+	if (!atomic_read(&group->container_users))
+		return 0;
+
+	return vfio_dev_viable(dev, group);
+}
+
+static int vfio_iommu_group_notifier(struct notifier_block *nb,
+				     unsigned long action, void *data)
+{
+	struct vfio_group *group = container_of(nb, struct vfio_group, nb);
+	struct device *dev = data;
+
+	/*
+	 * Need to go through a group_lock lookup to get a reference or we
+	 * risk racing a group being removed.  Ignore spurious notifies.
+	 */
+	group = vfio_group_try_get(group);
+	if (!group)
+		return NOTIFY_OK;
+
+	switch (action) {
+	case IOMMU_GROUP_NOTIFY_ADD_DEVICE:
+		vfio_group_nb_add_dev(group, dev);
+		break;
+	case IOMMU_GROUP_NOTIFY_DEL_DEVICE:
+		/*
+		 * Nothing to do here.  If the device is in use, then the
+		 * vfio sub-driver should block the remove callback until
+		 * it is unused.  If the device is unused or attached to a
+		 * stub driver, then it should be released and we don't
+		 * care that it will be going away.
+		 */
+		break;
+	case IOMMU_GROUP_NOTIFY_BIND_DRIVER:
+		pr_debug("%s: Device %s, group %d binding to driver\n",
+			 __func__, dev_name(dev),
+			 iommu_group_id(group->iommu_group));
+		break;
+	case IOMMU_GROUP_NOTIFY_BOUND_DRIVER:
+		pr_debug("%s: Device %s, group %d bound to driver %s\n",
+			 __func__, dev_name(dev),
+			 iommu_group_id(group->iommu_group), dev->driver->name);
+		BUG_ON(vfio_group_nb_verify(group, dev));
+		break;
+	case IOMMU_GROUP_NOTIFY_UNBIND_DRIVER:
+		pr_debug("%s: Device %s, group %d unbinding from driver %s\n",
+			 __func__, dev_name(dev),
+			 iommu_group_id(group->iommu_group), dev->driver->name);
+		break;
+	case IOMMU_GROUP_NOTIFY_UNBOUND_DRIVER:
+		pr_debug("%s: Device %s, group %d unbound from driver\n",
+			 __func__, dev_name(dev),
+			 iommu_group_id(group->iommu_group));
+		/*
+		 * XXX An unbound device in a live group is ok, but we'd
+		 * really like to avoid the above BUG_ON by preventing other
+		 * drivers from binding to it.  Once that occurs, we have to
+		 * stop the system to maintain isolation.  At a minimum, we'd
+		 * want a toggle to disable driver auto probe for this device.
+		 */
+		break;
+	}
+
+	vfio_group_put(group);
+	return NOTIFY_OK;
+}
+
+/**
+ * VFIO driver API
+ */
+int vfio_add_group_dev(struct device *dev,
+		       const struct vfio_device_ops *ops, void *device_data)
+{
+	struct iommu_group *iommu_group;
+	struct vfio_group *group;
+	struct vfio_device *device;
+
+	iommu_group = iommu_group_get(dev);
+	if (!iommu_group)
+		return -EINVAL;
+
+	group = vfio_group_get_from_iommu(iommu_group);
+	if (!group) {
+		group = vfio_create_group(iommu_group);
+		if (IS_ERR(group)) {
+			iommu_group_put(iommu_group);
+			return PTR_ERR(group);
+		}
+	}
+
+	device = vfio_group_get_device(group, dev);
+	if (device) {
+		WARN(1, "Device %s already exists on group %d\n",
+		     dev_name(dev), iommu_group_id(iommu_group));
+		vfio_device_put(device);
+		vfio_group_put(group);
+		iommu_group_put(iommu_group);
+		return -EBUSY;
+	}
+
+	device = vfio_group_create_device(group, dev, ops, device_data);
+	if (IS_ERR(device)) {
+		vfio_group_put(group);
+		iommu_group_put(iommu_group);
+		return PTR_ERR(device);
+	}
+
+	/*
+	 * Added device holds reference to iommu_group and vfio_device
+	 * (which in turn holds reference to vfio_group).  Drop extra
+	 * group reference used while acquiring device.
+	 */
+	vfio_group_put(group);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(vfio_add_group_dev);
+
+/**
+ * Get a reference to the vfio_device for a device that is known to
+ * be bound to a vfio driver.  The driver implicitly holds a
+ * vfio_device reference between vfio_add_group_dev and
+ * vfio_del_group_dev.  We can therefore use drvdata to increment
+ * that reference from the struct device.  This additional
+ * reference must be released by calling vfio_device_put.
+ */
+struct vfio_device *vfio_device_get_from_dev(struct device *dev)
+{
+	struct vfio_device *device = dev_get_drvdata(dev);
+
+	vfio_device_get(device);
+
+	return device;
+}
+EXPORT_SYMBOL_GPL(vfio_device_get_from_dev);
+
+/*
+ * Caller must hold a reference to the vfio_device
+ */
+void *vfio_device_data(struct vfio_device *device)
+{
+	return device->device_data;
+}
+EXPORT_SYMBOL_GPL(vfio_device_data);
+
+/* Given a referenced group, check if it contains the device */
+static bool vfio_dev_present(struct vfio_group *group, struct device *dev)
+{
+	struct vfio_device *device;
+
+	device = vfio_group_get_device(group, dev);
+	if (!device)
+		return false;
+
+	vfio_device_put(device);
+	return true;
+}
+
+/*
+ * Decrement the device reference count and wait for the device to be
+ * removed.  Open file descriptors for the device... */
+void *vfio_del_group_dev(struct device *dev)
+{
+	struct vfio_device *device = dev_get_drvdata(dev);
+	struct vfio_group *group = device->group;
+	struct iommu_group *iommu_group = group->iommu_group;
+	void *device_data = device->device_data;
+
+	/*
+	 * The group exists so long as we have a device reference.  Get
+	 * a group reference and use it to scan for the device going away.
+	 */
+	vfio_group_get(group);
+
+	vfio_device_put(device);
+
+	/* TODO send a signal to encourage this to be released */
+	wait_event(vfio.release_q, !vfio_dev_present(group, dev));
+
+	vfio_group_put(group);
+
+	iommu_group_put(iommu_group);
+
+	return device_data;
+}
+EXPORT_SYMBOL_GPL(vfio_del_group_dev);
+
+/**
+ * VFIO base fd, /dev/vfio/vfio
+ */
+static long vfio_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 (!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);
+		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 (!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;
+		}
+
+		/* module reference holds the driver we're working on */
+		mutex_unlock(&vfio.iommu_drivers_lock);
+
+		data = driver->ops->open(arg);
+		if (IS_ERR(data)) {
+			ret = PTR_ERR(data);
+			module_put(driver->ops->owner);
+			goto skip_drivers_unlock;
+		}
+
+		ret = __vfio_container_attach_groups(container, driver, data);
+		if (!ret) {
+			container->iommu_driver = driver;
+			container->iommu_data = data;
+		} else {
+			driver->ops->release(data);
+			module_put(driver->ops->owner);
+		}
+
+		goto skip_drivers_unlock;
+	}
+
+	mutex_unlock(&vfio.iommu_drivers_lock);
+skip_drivers_unlock:
+	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_ioctl_check_extension(container, arg);
+		break;
+	case VFIO_SET_IOMMU:
+		ret = vfio_ioctl_set_iommu(container, arg);
+		break;
+	default:
+		down_read(&container->group_lock);
+
+		driver = container->iommu_driver;
+		data = container->iommu_data;
+
+		if (driver) /* passthrough all unrecognized ioctls */
+			ret = driver->ops->ioctl(data, cmd, arg);
+
+		up_read(&container->group_lock);
+	}
+
+	return ret;
+}
+
+#ifdef CONFIG_COMPAT
+static long vfio_fops_compat_ioctl(struct file *filep,
+				   unsigned int cmd, unsigned long arg)
+{
+	arg = (unsigned long)compat_ptr(arg);
+	return vfio_fops_unl_ioctl(filep, cmd, arg);
+}
+#endif	/* CONFIG_COMPAT */
+
+static int vfio_fops_open(struct inode *inode, struct file *filep)
+{
+	struct vfio_container *container;
+
+	container = kzalloc(sizeof(*container), GFP_KERNEL);
+	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;
+}
+
+/*
+ * Once an iommu driver is set, we optionally pass read/write/mmap
+ * on to the driver, allowing management interfaces beyond ioctl.
+ */
+static ssize_t vfio_fops_read(struct file *filep, char __user *buf,
+			      size_t count, loff_t *ppos)
+{
+	struct vfio_container *container = filep->private_data;
+	struct vfio_iommu_driver *driver;
+	ssize_t ret = -EINVAL;
+
+	down_read(&container->group_lock);
+
+	driver = container->iommu_driver;
+	if (likely(driver && driver->ops->read))
+		ret = driver->ops->read(container->iommu_data,
+					buf, count, ppos);
+
+	up_read(&container->group_lock);
+
+	return ret;
+}
+
+static ssize_t vfio_fops_write(struct file *filep, const char __user *buf,
+			       size_t count, loff_t *ppos)
+{
+	struct vfio_container *container = filep->private_data;
+	struct vfio_iommu_driver *driver;
+	ssize_t ret = -EINVAL;
+
+	down_read(&container->group_lock);
+
+	driver = container->iommu_driver;
+	if (likely(driver && driver->ops->write))
+		ret = driver->ops->write(container->iommu_data,
+					 buf, count, ppos);
+
+	up_read(&container->group_lock);
+
+	return ret;
+}
+
+static int vfio_fops_mmap(struct file *filep, struct vm_area_struct *vma)
+{
+	struct vfio_container *container = filep->private_data;
+	struct vfio_iommu_driver *driver;
+	int ret = -EINVAL;
+
+	down_read(&container->group_lock);
+
+	driver = container->iommu_driver;
+	if (likely(driver && driver->ops->mmap))
+		ret = driver->ops->mmap(container->iommu_data, vma);
+
+	up_read(&container->group_lock);
+
+	return ret;
+}
+
+static const struct file_operations vfio_fops = {
+	.owner		= THIS_MODULE,
+	.open		= vfio_fops_open,
+	.release	= vfio_fops_release,
+	.read		= vfio_fops_read,
+	.write		= vfio_fops_write,
+	.unlocked_ioctl	= vfio_fops_unl_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl	= vfio_fops_compat_ioctl,
+#endif
+	.mmap		= vfio_fops_mmap,
+};
+
+/**
+ * VFIO Group fd, /dev/vfio/$GROUP
+ */
+static void __vfio_group_unset_container(struct vfio_group *group)
+{
+	struct vfio_container *container = group->container;
+	struct vfio_iommu_driver *driver;
+
+	down_write(&container->group_lock);
+
+	driver = container->iommu_driver;
+	if (driver)
+		driver->ops->detach_group(container->iommu_data,
+					  group->iommu_group);
+
+	group->container = NULL;
+	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);
+}
+
+/*
+ * VFIO_GROUP_UNSET_CONTAINER should fail if there are other users or
+ * if there was no container to unset.  Since the ioctl is called on
+ * the group, we know that still exists, therefore the only valid
+ * transition here is 1->0.
+ */
+static int vfio_group_unset_container(struct vfio_group *group)
+{
+	int users = atomic_cmpxchg(&group->container_users, 1, 0);
+
+	if (!users)
+		return -EINVAL;
+	if (users != 1)
+		return -EBUSY;
+
+	__vfio_group_unset_container(group);
+
+	return 0;
+}
+
+/*
+ * When removing container users, anything that removes the last user
+ * implicitly removes the group from the container.  That is, if the
+ * group file descriptor is closed, as well as any device file descriptors,
+ * the group is free.
+ */
+static void vfio_group_try_dissolve_container(struct vfio_group *group)
+{
+	if (0 == atomic_dec_if_positive(&group->container_users))
+		__vfio_group_unset_container(group);
+}
+
+static int vfio_group_set_container(struct vfio_group *group, int container_fd)
+{
+	struct fd f;
+	struct vfio_container *container;
+	struct vfio_iommu_driver *driver;
+	int ret = 0;
+
+	if (atomic_read(&group->container_users))
+		return -EINVAL;
+
+	f = fdget(container_fd);
+	if (!f.file)
+		return -EBADF;
+
+	/* Sanity check, is this really our fd? */
+	if (f.file->f_op != &vfio_fops) {
+		fdput(f);
+		return -EINVAL;
+	}
+
+	container = f.file->private_data;
+	WARN_ON(!container); /* fget ensures we don't race vfio_release */
+
+	down_write(&container->group_lock);
+
+	driver = container->iommu_driver;
+	if (driver) {
+		ret = driver->ops->attach_group(container->iommu_data,
+						group->iommu_group);
+		if (ret)
+			goto unlock_out;
+	}
+
+	group->container = container;
+	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);
+	atomic_inc(&group->container_users);
+
+unlock_out:
+	up_write(&container->group_lock);
+	fdput(f);
+	return ret;
+}
+
+static bool vfio_group_viable(struct vfio_group *group)
+{
+	return (iommu_group_for_each_dev(group->iommu_group,
+					 group, vfio_dev_viable) == 0);
+}
+
+static const struct file_operations vfio_device_fops;
+
+static int vfio_group_get_device_fd(struct vfio_group *group, char *buf)
+{
+	struct vfio_device *device;
+	struct file *filep;
+	int ret = -ENODEV;
+
+	if (0 == atomic_read(&group->container_users) ||
+	    !group->container->iommu_driver || !vfio_group_viable(group))
+		return -EINVAL;
+
+	mutex_lock(&group->device_lock);
+	list_for_each_entry(device, &group->device_list, group_next) {
+		if (strcmp(dev_name(device->dev), buf))
+			continue;
+
+		ret = device->ops->open(device->device_data);
+		if (ret)
+			break;
+		/*
+		 * We can't use anon_inode_getfd() because we need to modify
+		 * the f_mode flags directly to allow more than just ioctls
+		 */
+		ret = get_unused_fd_flags(O_CLOEXEC);
+		if (ret < 0) {
+			device->ops->release(device->device_data);
+			break;
+		}
+
+		filep = anon_inode_getfile("[vfio-device]", &vfio_device_fops,
+					   device, O_RDWR);
+		if (IS_ERR(filep)) {
+			put_unused_fd(ret);
+			ret = PTR_ERR(filep);
+			device->ops->release(device->device_data);
+			break;
+		}
+
+		/*
+		 * TODO: add an anon_inode interface to do this.
+		 * Appears to be missing by lack of need rather than
+		 * explicitly prevented.  Now there's need.
+		 */
+		filep->f_mode |= (FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
+
+		vfio_device_get(device);
+		atomic_inc(&group->container_users);
+
+		fd_install(ret, filep);
+		break;
+	}
+	mutex_unlock(&group->device_lock);
+
+	return ret;
+}
+
+static long vfio_group_fops_unl_ioctl(struct file *filep,
+				      unsigned int cmd, unsigned long arg)
+{
+	struct vfio_group *group = filep->private_data;
+	long ret = -ENOTTY;
+
+	switch (cmd) {
+	case VFIO_GROUP_GET_STATUS:
+	{
+		struct vfio_group_status status;
+		unsigned long minsz;
+
+		minsz = offsetofend(struct vfio_group_status, flags);
+
+		if (copy_from_user(&status, (void __user *)arg, minsz))
+			return -EFAULT;
+
+		if (status.argsz < minsz)
+			return -EINVAL;
+
+		status.flags = 0;
+
+		if (vfio_group_viable(group))
+			status.flags |= VFIO_GROUP_FLAGS_VIABLE;
+
+		if (group->container)
+			status.flags |= VFIO_GROUP_FLAGS_CONTAINER_SET;
+
+		if (copy_to_user((void __user *)arg, &status, minsz))
+			return -EFAULT;
+
+		ret = 0;
+		break;
+	}
+	case VFIO_GROUP_SET_CONTAINER:
+	{
+		int fd;
+
+		if (get_user(fd, (int __user *)arg))
+			return -EFAULT;
+
+		if (fd < 0)
+			return -EINVAL;
+
+		ret = vfio_group_set_container(group, fd);
+		break;
+	}
+	case VFIO_GROUP_UNSET_CONTAINER:
+		ret = vfio_group_unset_container(group);
+		break;
+	case VFIO_GROUP_GET_DEVICE_FD:
+	{
+		char *buf;
+
+		buf = strndup_user((const char __user *)arg, PAGE_SIZE);
+		if (IS_ERR(buf))
+			return PTR_ERR(buf);
+
+		ret = vfio_group_get_device_fd(group, buf);
+		kfree(buf);
+		break;
+	}
+	}
+
+	return ret;
+}
+
+#ifdef CONFIG_COMPAT
+static long vfio_group_fops_compat_ioctl(struct file *filep,
+					 unsigned int cmd, unsigned long arg)
+{
+	arg = (unsigned long)compat_ptr(arg);
+	return vfio_group_fops_unl_ioctl(filep, cmd, arg);
+}
+#endif	/* CONFIG_COMPAT */
+
+static int vfio_group_fops_open(struct inode *inode, struct file *filep)
+{
+	struct vfio_group *group;
+	int opened;
+
+	group = vfio_group_get_from_minor(iminor(inode));
+	if (!group)
+		return -ENODEV;
+
+	/* Do we need multiple instances of the group open?  Seems not. */
+	opened = atomic_cmpxchg(&group->opened, 0, 1);
+	if (opened) {
+		vfio_group_put(group);
+		return -EBUSY;
+	}
+
+	/* Is something still in use from a previous open? */
+	if (group->container) {
+		atomic_dec(&group->opened);
+		vfio_group_put(group);
+		return -EBUSY;
+	}
+
+	filep->private_data = group;
+
+	return 0;
+}
+
+static int vfio_group_fops_release(struct inode *inode, struct file *filep)
+{
+	struct vfio_group *group = filep->private_data;
+
+	filep->private_data = NULL;
+
+	vfio_group_try_dissolve_container(group);
+
+	atomic_dec(&group->opened);
+
+	vfio_group_put(group);
+
+	return 0;
+}
+
+static const struct file_operations vfio_group_fops = {
+	.owner		= THIS_MODULE,
+	.unlocked_ioctl	= vfio_group_fops_unl_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl	= vfio_group_fops_compat_ioctl,
+#endif
+	.open		= vfio_group_fops_open,
+	.release	= vfio_group_fops_release,
+};
+
+/**
+ * VFIO Device fd
+ */
+static int vfio_device_fops_release(struct inode *inode, struct file *filep)
+{
+	struct vfio_device *device = filep->private_data;
+
+	device->ops->release(device->device_data);
+
+	vfio_group_try_dissolve_container(device->group);
+
+	vfio_device_put(device);
+
+	return 0;
+}
+
+static long vfio_device_fops_unl_ioctl(struct file *filep,
+				       unsigned int cmd, unsigned long arg)
+{
+	struct vfio_device *device = filep->private_data;
+
+	if (unlikely(!device->ops->ioctl))
+		return -EINVAL;
+
+	return device->ops->ioctl(device->device_data, cmd, arg);
+}
+
+static ssize_t vfio_device_fops_read(struct file *filep, char __user *buf,
+				     size_t count, loff_t *ppos)
+{
+	struct vfio_device *device = filep->private_data;
+
+	if (unlikely(!device->ops->read))
+		return -EINVAL;
+
+	return device->ops->read(device->device_data, buf, count, ppos);
+}
+
+static ssize_t vfio_device_fops_write(struct file *filep,
+				      const char __user *buf,
+				      size_t count, loff_t *ppos)
+{
+	struct vfio_device *device = filep->private_data;
+
+	if (unlikely(!device->ops->write))
+		return -EINVAL;
+
+	return device->ops->write(device->device_data, buf, count, ppos);
+}
+
+static int vfio_device_fops_mmap(struct file *filep, struct vm_area_struct *vma)
+{
+	struct vfio_device *device = filep->private_data;
+
+	if (unlikely(!device->ops->mmap))
+		return -EINVAL;
+
+	return device->ops->mmap(device->device_data, vma);
+}
+
+#ifdef CONFIG_COMPAT
+static long vfio_device_fops_compat_ioctl(struct file *filep,
+					  unsigned int cmd, unsigned long arg)
+{
+	arg = (unsigned long)compat_ptr(arg);
+	return vfio_device_fops_unl_ioctl(filep, cmd, arg);
+}
+#endif	/* CONFIG_COMPAT */
+
+static const struct file_operations vfio_device_fops = {
+	.owner		= THIS_MODULE,
+	.release	= vfio_device_fops_release,
+	.read		= vfio_device_fops_read,
+	.write		= vfio_device_fops_write,
+	.unlocked_ioctl	= vfio_device_fops_unl_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl	= vfio_device_fops_compat_ioctl,
+#endif
+	.mmap		= vfio_device_fops_mmap,
+};
+
+/**
+ * External user API, exported by symbols to be linked dynamically.
+ *
+ * The protocol includes:
+ *  1. do normal VFIO init operation:
+ *	- opening a new container;
+ *	- attaching group(s) to it;
+ *	- setting an IOMMU driver for a container.
+ * When IOMMU is set for a container, all groups in it are
+ * considered ready to use by an external user.
+ *
+ * 2. User space passes a group fd to an external user.
+ * The external user calls vfio_group_get_external_user()
+ * to verify that:
+ *	- the group is initialized;
+ *	- IOMMU is set for it.
+ * If both checks passed, vfio_group_get_external_user()
+ * increments the container user counter to prevent
+ * the VFIO group from disposal before KVM exits.
+ *
+ * 3. The external user calls vfio_external_user_iommu_id()
+ * to know an IOMMU ID.
+ *
+ * 4. When the external KVM finishes, it calls
+ * vfio_group_put_external_user() to release the VFIO group.
+ * This call decrements the container user counter.
+ */
+struct vfio_group *vfio_group_get_external_user(struct file *filep)
+{
+	struct vfio_group *group = filep->private_data;
+
+	if (filep->f_op != &vfio_group_fops)
+		return ERR_PTR(-EINVAL);
+
+	if (!atomic_inc_not_zero(&group->container_users))
+		return ERR_PTR(-EINVAL);
+
+	if (!group->container->iommu_driver ||
+			!vfio_group_viable(group)) {
+		atomic_dec(&group->container_users);
+		return ERR_PTR(-EINVAL);
+	}
+
+	vfio_group_get(group);
+
+	return group;
+}
+EXPORT_SYMBOL_GPL(vfio_group_get_external_user);
+
+void vfio_group_put_external_user(struct vfio_group *group)
+{
+	vfio_group_put(group);
+	vfio_group_try_dissolve_container(group);
+}
+EXPORT_SYMBOL_GPL(vfio_group_put_external_user);
+
+int vfio_external_user_iommu_id(struct vfio_group *group)
+{
+	return iommu_group_id(group->iommu_group);
+}
+EXPORT_SYMBOL_GPL(vfio_external_user_iommu_id);
+
+long vfio_external_check_extension(struct vfio_group *group, unsigned long arg)
+{
+	return vfio_ioctl_check_extension(group->container, arg);
+}
+EXPORT_SYMBOL_GPL(vfio_external_check_extension);
+
+/**
+ * Module/class support
+ */
+static char *vfio_devnode(struct device *dev, umode_t *mode)
+{
+	return kasprintf(GFP_KERNEL, "vfio/%s", dev_name(dev));
+}
+
+static struct miscdevice vfio_dev = {
+	.minor = VFIO_MINOR,
+	.name = "vfio",
+	.fops = &vfio_fops,
+	.nodename = "vfio/vfio",
+	.mode = S_IRUGO | S_IWUGO,
+};
+
+static int __init vfio_init(void)
+{
+	int ret;
+
+	idr_init(&vfio.group_idr);
+	mutex_init(&vfio.group_lock);
+	mutex_init(&vfio.iommu_drivers_lock);
+	INIT_LIST_HEAD(&vfio.group_list);
+	INIT_LIST_HEAD(&vfio.iommu_drivers_list);
+	init_waitqueue_head(&vfio.release_q);
+
+	ret = misc_register(&vfio_dev);
+	if (ret) {
+		pr_err("vfio: misc device register failed\n");
+		return ret;
+	}
+
+	/* /dev/vfio/$GROUP */
+	vfio.class = class_create(THIS_MODULE, "vfio");
+	if (IS_ERR(vfio.class)) {
+		ret = PTR_ERR(vfio.class);
+		goto err_class;
+	}
+
+	vfio.class->devnode = vfio_devnode;
+
+	ret = alloc_chrdev_region(&vfio.group_devt, 0, MINORMASK, "vfio");
+	if (ret)
+		goto err_alloc_chrdev;
+
+	cdev_init(&vfio.group_cdev, &vfio_group_fops);
+	ret = cdev_add(&vfio.group_cdev, vfio.group_devt, MINORMASK);
+	if (ret)
+		goto err_cdev_add;
+
+	pr_info(DRIVER_DESC " version: " DRIVER_VERSION "\n");
+
+	/*
+	 * Attempt to load known iommu-drivers.  This gives us a working
+	 * environment without the user needing to explicitly load iommu
+	 * drivers.
+	 */
+	request_module_nowait("vfio_iommu_type1");
+	request_module_nowait("vfio_iommu_spapr_tce");
+
+	return 0;
+
+err_cdev_add:
+	unregister_chrdev_region(vfio.group_devt, MINORMASK);
+err_alloc_chrdev:
+	class_destroy(vfio.class);
+	vfio.class = NULL;
+err_class:
+	misc_deregister(&vfio_dev);
+	return ret;
+}
+
+static void __exit vfio_cleanup(void)
+{
+	WARN_ON(!list_empty(&vfio.group_list));
+
+	idr_destroy(&vfio.group_idr);
+	cdev_del(&vfio.group_cdev);
+	unregister_chrdev_region(vfio.group_devt, MINORMASK);
+	class_destroy(vfio.class);
+	vfio.class = NULL;
+	misc_deregister(&vfio_dev);
+}
+
+module_init(vfio_init);
+module_exit(vfio_cleanup);
+
+MODULE_VERSION(DRIVER_VERSION);
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_ALIAS_MISCDEV(VFIO_MINOR);
+MODULE_ALIAS("devname:vfio/vfio");