Commit 3ca54708 authored by Jason Gunthorpe's avatar Jason Gunthorpe Committed by Alex Williamson
Browse files

vfio: Change struct vfio_group::container_users to a non-atomic int 



Now that everything is fully locked there is no need for container_users
to remain as an atomic, change it to an unsigned int.

Use 'if (group->container)' as the test to determine if the container is
present or not instead of using container_users.

Reviewed-by: default avatarKevin Tian <kevin.tian@intel.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Tested-by: default avatarNicolin Chen <nicolinc@nvidia.com>
Tested-by: default avatarMatthew Rosato <mjrosato@linux.ibm.com>
Link: https://lore.kernel.org/r/6-v2-d035a1842d81+1bf-vfio_group_locking_jgg@nvidia.com


Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
parent b76c0eed

drivers/vfio/vfio.c

+13 −15
Original line number Diff line number Diff line
@@ -66,7 +66,7 @@ struct vfio_group { 
	struct device 			dev;

	struct cdev			cdev;

	refcount_t			users;

	atomic_t			container_users;

	unsigned int			container_users;

	struct iommu_group		*iommu_group;

	struct vfio_container		*container;

	struct list_head		device_list;
@@ -429,7 +429,7 @@ static void vfio_group_put(struct vfio_group *group) 
	 * properly hold the group reference.

	 */

	WARN_ON(!list_empty(&group->device_list));

	WARN_ON(atomic_read(&group->container_users));

	WARN_ON(group->container || group->container_users);

	WARN_ON(group->notifier.head);



	list_del(&group->vfio_next);
@@ -930,6 +930,7 @@ static void __vfio_group_unset_container(struct vfio_group *group) 
	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 */
@@ -953,17 +954,13 @@ static void __vfio_group_unset_container(struct vfio_group *group) 
 */

static int vfio_group_unset_container(struct vfio_group *group)

{

	int users = atomic_cmpxchg(&group->container_users, 1, 0);



	lockdep_assert_held_write(&group->group_rwsem);



	if (!users)

	if (!group->container)

		return -EINVAL;

	if (users != 1)

	if (group->container_users != 1)

		return -EBUSY;



	__vfio_group_unset_container(group);



	return 0;

}
@@ -976,7 +973,7 @@ static int vfio_group_set_container(struct vfio_group *group, int container_fd) 


	lockdep_assert_held_write(&group->group_rwsem);



	if (atomic_read(&group->container_users))

	if (group->container || WARN_ON(group->container_users))

		return -EINVAL;



	if (group->type == VFIO_NO_IOMMU && !capable(CAP_SYS_RAWIO))
@@ -1020,12 +1017,12 @@ static int vfio_group_set_container(struct vfio_group *group, int container_fd) 
	}



	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);

	atomic_inc(&group->container_users);



unlock_out:

	up_write(&container->group_lock);
@@ -1047,22 +1044,23 @@ static int vfio_device_assign_container(struct vfio_device *device) 


	lockdep_assert_held_write(&group->group_rwsem);



	if (0 == atomic_read(&group->container_users) ||

	    !group->container->iommu_driver)

	if (!group->container || !group->container->iommu_driver ||

	    WARN_ON(!group->container_users))

		return -EINVAL;



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

		return -EPERM;



	get_file(group->opened_file);

	atomic_inc(&group->container_users);

	group->container_users++;

	return 0;

}



static void vfio_device_unassign_container(struct vfio_device *device)

{

	down_write(&device->group->group_rwsem);

	atomic_dec(&device->group->container_users);

	WARN_ON(device->group->container_users <= 1);

	device->group->container_users--;

	fput(device->group->opened_file);

	up_write(&device->group->group_rwsem);

}
@@ -1289,7 +1287,7 @@ static int vfio_group_fops_release(struct inode *inode, struct file *filep) 
	 */

	WARN_ON(group->notifier.head);

	if (group->container) {

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

		WARN_ON(group->container_users != 1);

		__vfio_group_unset_container(group);

	}

	group->opened_file = NULL;