On Wed, 02 Mar 2022 17:07:21 +0100 Cornelia Huck <cohuck@xxxxxxxxxx> wrote: > On Wed, Mar 02 2022, Alex Williamson <alex.williamson@xxxxxxxxxx> wrote: > > > 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 > > So, should the function then write anything to next_fsm if it returns > -errno? (Maybe I'm misunderstanding.) Or should the caller always expect > that something may be written to new_fsm, and simply only look at it if > the function returns success? Note that this function doesn't actually transition the device to next_fsm, it's only informing the driver what the next state is. Therefore I think it's reasonable to expect that the caller is never going to use it's actual internal device state for next_fsm. So I don't really see a case where we need to worry about preserving next_fsm in the error condition. Thanks, Alex
