Commit 1c26c3bb authored by Nicolin Chen's avatar Nicolin Chen Committed by Jason Gunthorpe
Browse files

iommufd/access: Add internal APIs for HW queue to use 

The new HW queue object, as an internal iommufd object, wants to reuse the
struct iommufd_access to pin some iova range in the iopt.

However, an access generally takes the refcount of an ictx. So, in such an
internal case, a deadlock could happen when the release of the ictx has to
wait for the release of the access first when releasing a hw_queue object,
which could wait for the release of the ictx that is refcounted:
    ictx --releases--> hw_queue --releases--> access
      ^                                         |
      |_________________releases________________v

To address this, add a set of lightweight internal APIs to unlink the ictx
and the access, i.e. no ictx refcounting by the access:
    ictx --releases--> hw_queue --releases--> access

Then, there's no point in setting the access->ictx. So simply define !ictx
as an flag for an internal use and add an inline helper.

Link: https://patch.msgid.link/r/d8d84bf99cbebec56034b57b966a3d431385b90d.1752126748.git.nicolinc@nvidia.com


Reviewed-by: default avatarKevin Tian <kevin.tian@intel.com>
Reviewed-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Signed-off-by: default avatarNicolin Chen <nicolinc@nvidia.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@nvidia.com>
parent 0e3e0b0c

drivers/iommu/iommufd/device.c

+50 −9
Original line number Diff line number Diff line
@@ -1084,9 +1084,41 @@ void iommufd_access_destroy_object(struct iommufd_object *obj) 
	if (access->ioas)

		WARN_ON(iommufd_access_change_ioas(access, NULL));

	mutex_unlock(&access->ioas_lock);

	if (!iommufd_access_is_internal(access))

		iommufd_ctx_put(access->ictx);

}



static struct iommufd_access *__iommufd_access_create(struct iommufd_ctx *ictx)

{

	struct iommufd_access *access;



	/*

	 * There is no uAPI for the access object, but to keep things symmetric

	 * use the object infrastructure anyhow.

	 */

	access = iommufd_object_alloc(ictx, access, IOMMUFD_OBJ_ACCESS);

	if (IS_ERR(access))

		return access;



	/* The calling driver is a user until iommufd_access_destroy() */

	refcount_inc(&access->obj.users);

	mutex_init(&access->ioas_lock);

	return access;

}



struct iommufd_access *iommufd_access_create_internal(struct iommufd_ctx *ictx)

{

	struct iommufd_access *access;



	access = __iommufd_access_create(ictx);

	if (IS_ERR(access))

		return access;

	access->iova_alignment = PAGE_SIZE;



	iommufd_object_finalize(ictx, &access->obj);

	return access;

}



/**

 * iommufd_access_create - Create an iommufd_access

 * @ictx: iommufd file descriptor
@@ -1106,11 +1138,7 @@ iommufd_access_create(struct iommufd_ctx *ictx, 
{

	struct iommufd_access *access;



	/*

	 * There is no uAPI for the access object, but to keep things symmetric

	 * use the object infrastructure anyhow.

	 */

	access = iommufd_object_alloc(ictx, access, IOMMUFD_OBJ_ACCESS);

	access = __iommufd_access_create(ictx);

	if (IS_ERR(access))

		return access;
@@ -1122,13 +1150,10 @@ iommufd_access_create(struct iommufd_ctx *ictx, 
	else

		access->iova_alignment = 1;



	/* The calling driver is a user until iommufd_access_destroy() */

	refcount_inc(&access->obj.users);

	access->ictx = ictx;

	iommufd_ctx_get(ictx);

	iommufd_object_finalize(ictx, &access->obj);

	*id = access->obj.id;

	mutex_init(&access->ioas_lock);

	return access;

}

EXPORT_SYMBOL_NS_GPL(iommufd_access_create, "IOMMUFD");
@@ -1173,6 +1198,22 @@ int iommufd_access_attach(struct iommufd_access *access, u32 ioas_id) 
}

EXPORT_SYMBOL_NS_GPL(iommufd_access_attach, "IOMMUFD");



int iommufd_access_attach_internal(struct iommufd_access *access,

				   struct iommufd_ioas *ioas)

{

	int rc;



	mutex_lock(&access->ioas_lock);

	if (WARN_ON(access->ioas)) {

		mutex_unlock(&access->ioas_lock);

		return -EINVAL;

	}



	rc = iommufd_access_change_ioas(access, ioas);

	mutex_unlock(&access->ioas_lock);

	return rc;

}



int iommufd_access_replace(struct iommufd_access *access, u32 ioas_id)

{

	int rc;

drivers/iommu/iommufd/iommufd_private.h

+23 −0
Original line number Diff line number Diff line
@@ -484,6 +484,29 @@ void iopt_remove_access(struct io_pagetable *iopt, 
			struct iommufd_access *access, u32 iopt_access_list_id);

void iommufd_access_destroy_object(struct iommufd_object *obj);



/* iommufd_access for internal use */

static inline bool iommufd_access_is_internal(struct iommufd_access *access)

{

	return !access->ictx;

}



struct iommufd_access *iommufd_access_create_internal(struct iommufd_ctx *ictx);



static inline void

iommufd_access_destroy_internal(struct iommufd_ctx *ictx,

				struct iommufd_access *access)

{

	iommufd_object_destroy_user(ictx, &access->obj);

}



int iommufd_access_attach_internal(struct iommufd_access *access,

				   struct iommufd_ioas *ioas);



static inline void iommufd_access_detach_internal(struct iommufd_access *access)

{

	iommufd_access_detach(access);

}



struct iommufd_eventq {

	struct iommufd_object obj;

	struct iommufd_ctx *ictx;