Commit 9227da78 authored by Nicolin Chen's avatar Nicolin Chen Committed by Jason Gunthorpe
Browse files

iommufd: Add iommufd_access_change_ioas(_id) helpers 

The complication of the mutex and refcount will be amplified after we
introduce the replace support for accesses. So, add a preparatory change
of a constitutive helper iommufd_access_change_ioas() and its wrapper
iommufd_access_change_ioas_id(). They can simply take care of existing
iommufd_access_attach() and iommufd_access_detach(), properly sequencing
the refcount puts so that they are truely at the end of the sequence after
we know the IOAS pointer is not required any more.

Link: https://lore.kernel.org/r/da0c462532193b447329c4eb975a596f47e49b70.1690523699.git.nicolinc@nvidia.com


Suggested-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Reviewed-by: default avatarKevin Tian <kevin.tian@intel.com>
Signed-off-by: default avatarNicolin Chen <nicolinc@nvidia.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@nvidia.com>
parent 5d5c85ff

drivers/iommu/iommufd/device.c

+71 −38
Original line number Diff line number Diff line
@@ -684,6 +684,70 @@ void iommufd_device_detach(struct iommufd_device *idev) 
}

EXPORT_SYMBOL_NS_GPL(iommufd_device_detach, IOMMUFD);



/*

 * On success, it will refcount_inc() at a valid new_ioas and refcount_dec() at

 * a valid cur_ioas (access->ioas). A caller passing in a valid new_ioas should

 * call iommufd_put_object() if it does an iommufd_get_object() for a new_ioas.

 */

static int iommufd_access_change_ioas(struct iommufd_access *access,

				      struct iommufd_ioas *new_ioas)

{

	u32 iopt_access_list_id = access->iopt_access_list_id;

	struct iommufd_ioas *cur_ioas = access->ioas;

	int rc;



	lockdep_assert_held(&access->ioas_lock);



	/* We are racing with a concurrent detach, bail */

	if (cur_ioas != access->ioas_unpin)

		return -EBUSY;



	if (cur_ioas == new_ioas)

		return 0;



	/*

	 * Set ioas to NULL to block any further iommufd_access_pin_pages().

	 * iommufd_access_unpin_pages() can continue using access->ioas_unpin.

	 */

	access->ioas = NULL;



	if (new_ioas) {

		rc = iopt_add_access(&new_ioas->iopt, access);

		if (rc) {

			access->ioas = cur_ioas;

			return rc;

		}

		refcount_inc(&new_ioas->obj.users);

	}



	if (cur_ioas) {

		if (access->ops->unmap) {

			mutex_unlock(&access->ioas_lock);

			access->ops->unmap(access->data, 0, ULONG_MAX);

			mutex_lock(&access->ioas_lock);

		}

		iopt_remove_access(&cur_ioas->iopt, access, iopt_access_list_id);

		refcount_dec(&cur_ioas->obj.users);

	}



	access->ioas = new_ioas;

	access->ioas_unpin = new_ioas;



	return 0;

}



static int iommufd_access_change_ioas_id(struct iommufd_access *access, u32 id)

{

	struct iommufd_ioas *ioas = iommufd_get_ioas(access->ictx, id);

	int rc;



	if (IS_ERR(ioas))

		return PTR_ERR(ioas);

	rc = iommufd_access_change_ioas(access, ioas);

	iommufd_put_object(&ioas->obj);

	return rc;

}



void iommufd_access_destroy_object(struct iommufd_object *obj)

{

	struct iommufd_access *access =
@@ -761,61 +825,30 @@ EXPORT_SYMBOL_NS_GPL(iommufd_access_destroy, IOMMUFD); 


void iommufd_access_detach(struct iommufd_access *access)

{

	struct iommufd_ioas *cur_ioas = access->ioas;



	mutex_lock(&access->ioas_lock);

	if (WARN_ON(!access->ioas))

		goto out;

	/*

	 * Set ioas to NULL to block any further iommufd_access_pin_pages().

	 * iommufd_access_unpin_pages() can continue using access->ioas_unpin.

	 */

	access->ioas = NULL;



	if (access->ops->unmap) {

	if (WARN_ON(!access->ioas)) {

		mutex_unlock(&access->ioas_lock);

		access->ops->unmap(access->data, 0, ULONG_MAX);

		mutex_lock(&access->ioas_lock);

		return;

	}

	iopt_remove_access(&cur_ioas->iopt, access,

			   access->iopt_access_list_id);

	refcount_dec(&cur_ioas->obj.users);

out:

	access->ioas_unpin = NULL;

	WARN_ON(iommufd_access_change_ioas(access, NULL));

	mutex_unlock(&access->ioas_lock);

}

EXPORT_SYMBOL_NS_GPL(iommufd_access_detach, IOMMUFD);



int iommufd_access_attach(struct iommufd_access *access, u32 ioas_id)

{

	struct iommufd_ioas *new_ioas;

	int rc = 0;

	int rc;



	mutex_lock(&access->ioas_lock);

	if (WARN_ON(access->ioas || access->ioas_unpin)) {

	if (WARN_ON(access->ioas)) {

		mutex_unlock(&access->ioas_lock);

		return -EINVAL;

	}



	new_ioas = iommufd_get_ioas(access->ictx, ioas_id);

	if (IS_ERR(new_ioas)) {

	rc = iommufd_access_change_ioas_id(access, ioas_id);

	mutex_unlock(&access->ioas_lock);

		return PTR_ERR(new_ioas);

	}



	rc = iopt_add_access(&new_ioas->iopt, access);

	if (rc) {

		mutex_unlock(&access->ioas_lock);

		iommufd_put_object(&new_ioas->obj);

	return rc;

}

	iommufd_ref_to_users(&new_ioas->obj);



	access->ioas = new_ioas;

	access->ioas_unpin = new_ioas;

	mutex_unlock(&access->ioas_lock);

	return 0;

}

EXPORT_SYMBOL_NS_GPL(iommufd_access_attach, IOMMUFD);



/**