Commit c6f4860e authored by Jason Gunthorpe's avatar Jason Gunthorpe Committed by Alex Williamson
Browse files

vfio: Change struct vfio_group::opened from an atomic to bool 



This is not a performance path, just use the group_rwsem to protect the
value.

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/2-v2-d035a1842d81+1bf-vfio_group_locking_jgg@nvidia.com


Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
parent be8d3ada

drivers/vfio/vfio.c

+27 −19
Original line number Diff line number Diff line
@@ -73,7 +73,7 @@ struct vfio_group { 
	struct mutex			device_lock;

	struct list_head		vfio_next;

	struct list_head		container_next;

	atomic_t			opened;

	bool				opened;

	enum vfio_group_type		type;

	unsigned int			dev_counter;

	struct rw_semaphore		group_rwsem;
@@ -1213,30 +1213,30 @@ static int vfio_group_fops_open(struct inode *inode, struct file *filep) 
{

	struct vfio_group *group =

		container_of(inode->i_cdev, struct vfio_group, cdev);

	int opened;

	int ret;



	/* users can be zero if this races with vfio_group_put() */

	if (!refcount_inc_not_zero(&group->users))

		return -ENODEV;

	down_write(&group->group_rwsem);



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

		vfio_group_put(group);

		return -EPERM;

	/* users can be zero if this races with vfio_group_put() */

	if (!refcount_inc_not_zero(&group->users)) {

		ret = -ENODEV;

		goto err_unlock;

	}



	/* 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;

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

		ret = -EPERM;

		goto err_put;

	}



	/* Is something still in use from a previous open? */

	if (group->container) {

		atomic_dec(&group->opened);

		vfio_group_put(group);

		return -EBUSY;

	/*

	 * Do we need multiple instances of the group open?  Seems not.

	 * Is something still in use from a previous open?

	 */

	if (group->opened || group->container) {

		ret = -EBUSY;

		goto err_put;

	}

	group->opened = true;



	/* Warn if previous user didn't cleanup and re-init to drop them */

	if (WARN_ON(group->notifier.head))
@@ -1244,7 +1244,13 @@ static int vfio_group_fops_open(struct inode *inode, struct file *filep) 


	filep->private_data = group;



	up_write(&group->group_rwsem);

	return 0;

err_put:

	vfio_group_put(group);

err_unlock:

	up_write(&group->group_rwsem);

	return ret;

}



static int vfio_group_fops_release(struct inode *inode, struct file *filep)
@@ -1255,7 +1261,9 @@ static int vfio_group_fops_release(struct inode *inode, struct file *filep) 


	vfio_group_try_dissolve_container(group);



	atomic_dec(&group->opened);

	down_write(&group->group_rwsem);

	group->opened = false;

	up_write(&group->group_rwsem);



	vfio_group_put(group);