vfio-iommufd: Make vfio_iommufd_emulated_bind() return iommufd_access ID

vfio device cdev needs to return iommufd_access ID to userspace if
bind_iommufd succeeds.

Link: https://lore.kernel.org/r/20230327093351.44505-5-yi.l.liu@intel.comReviewed-by: Kevin Tian <kevin.tian@intel.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Tested-by: Terrence Xu <terrence.xu@intel.com>
Tested-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/iommu/iommufd/device.c

@@ -425,6 +425,7 @@ void iommufd_access_destroy_object(struct iommufd_object *obj)
  * @ictx: iommufd file descriptor
  * @ops: Driver's ops to associate with the access
  * @data: Opaque data to pass into ops functions
+ * @id: Output ID number to return to userspace for this access
  *
  * An iommufd_access allows a driver to read/write to the IOAS without using
  * DMA. The underlying CPU memory can be accessed using the
@@ -434,7 +435,7 @@ void iommufd_access_destroy_object(struct iommufd_object *obj)
  */
 struct iommufd_access *
 iommufd_access_create(struct iommufd_ctx *ictx,
-		      const struct iommufd_access_ops *ops, void *data)
+		      const struct iommufd_access_ops *ops, void *data, u32 *id)
 {
 	struct iommufd_access *access;
 
@@ -459,6 +460,7 @@ iommufd_access_create(struct iommufd_ctx *ictx,
 	access->ictx = ictx;
 	iommufd_ctx_get(ictx);
 	iommufd_object_finalize(ictx, &access->obj);
+	*id = access->obj.id;
 	return access;
 }
 EXPORT_SYMBOL_NS_GPL(iommufd_access_create, IOMMUFD);

drivers/iommu/iommufd/selftest.c

@@ -554,6 +554,7 @@ static int iommufd_test_create_access(struct iommufd_ucmd *ucmd,
 	struct iommu_test_cmd *cmd = ucmd->cmd;
 	struct selftest_access *staccess;
 	struct iommufd_access *access;
+	u32 id;
 	int fdno;
 	int rc;
 
@@ -575,7 +576,7 @@ static int iommufd_test_create_access(struct iommufd_ucmd *ucmd,
 		(flags & MOCK_FLAGS_ACCESS_CREATE_NEEDS_PIN_PAGES) ?
 			&selftest_access_ops_pin :
 			&selftest_access_ops,
-		staccess);
+		staccess, &id);
 	if (IS_ERR(access)) {
 		rc = PTR_ERR(access);
 		goto out_put_fdno;

drivers/vfio/iommufd.c

@@ -142,7 +142,7 @@ int vfio_iommufd_emulated_bind(struct vfio_device *vdev,
 
 	lockdep_assert_held(&vdev->dev_set->lock);
 
-	user = iommufd_access_create(ictx, &vfio_user_ops, vdev);
+	user = iommufd_access_create(ictx, &vfio_user_ops, vdev, out_device_id);
 	if (IS_ERR(user))
 		return PTR_ERR(user);
 	vdev->iommufd_access = user;

include/linux/iommufd.h

@@ -41,7 +41,7 @@ enum {
 
 struct iommufd_access *
 iommufd_access_create(struct iommufd_ctx *ictx,
-		      const struct iommufd_access_ops *ops, void *data);
+		      const struct iommufd_access_ops *ops, void *data, u32 *id);
 void iommufd_access_destroy(struct iommufd_access *access);
 int iommufd_access_attach(struct iommufd_access *access, u32 ioas_id);