On Wed, 2 Mar 2022 10:27:32 -0400 Jason Gunthorpe <jgg@xxxxxxxxxx> wrote: > On Wed, Mar 02, 2022 at 12:19:20PM +0100, Cornelia Huck wrote: > > > +/* > > > + * vfio_mig_get_next_state - Compute the next step in the FSM > > > + * @cur_fsm - The current state the device is in > > > + * @new_fsm - The target state to reach > > > + * @next_fsm - Pointer to the next step to get to new_fsm > > > + * > > > + * Return 0 upon success, otherwise -errno > > > + * Upon success the next step in the state progression between cur_fsm and > > > + * new_fsm will be set in next_fsm. > > > > What about non-success? Can the caller make any assumption about > > next_fsm in that case? Because... > > I checked both mlx5 and acc, both properly ignore the next_fsm value > on error. This oddness aros when Alex asked to return an errno instead > of the state value. Right, my assertion was that only the driver itself should be able to transition to the ERROR state. vfio_mig_get_next_state() should never advise the driver to go to the error state, it can only report that a transition is invalid. The driver may stay in the current state if an error occurs here, which is why we added the ability to get the device state. Thanks, Alex > > > + * any -> ERROR > > > + * ERROR cannot be specified as a device state, however any transition request > > > + * can be failed with an errno return and may then move the device_state into > > > + * ERROR. In this case the device was unable to execute the requested arc and > > > + * was also unable to restore the device to any valid device_state. > > > + * To recover from ERROR VFIO_DEVICE_RESET must be used to return the > > > + * device_state back to RUNNING. > > > > ...this seems to indicate that not moving into STATE_ERROR is an > > option anyway. > > Yes, but it is never done by vfio_mig_get_next_state() it is only > directly triggered inside the driver. > > > Do we need any extra guidance in the description for > > vfio_mig_get_next_state()? > > I think no, it is typical in linux that function failure means output > arguments are not valid > > Jason >
