On Wed, Apr 08, 2020 at 04:48:02PM -0700, Jacob Pan wrote: > > Yes, this is the proper way, when the DMA is stopped and no use of the > > PASID remains then you can drop the mmu notifier and release the PASID > > entirely. If that is linked to the lifetime of the FD then forget > > completely about the mm_struct lifetime, it doesn't matter.. > > > Got everything above, thanks a lot. > > If everything is in order with the FD close. Why do we need to > "ask IOMMU drivers to silently abort DMA and Page Requests in the > meantime." in mm_exit notifier? This will be done orderly in unbind > anyway. I thought this is exactly what Jean-Phillippe is removing here, it is a bad idea for the reasons he explained. > > > Enforcing unbind upon FD close might be a precarious path, perhaps > > > that is why we have to deal with out of order situation? > > > > How so? You just put it in the FD release function :) > > I was thinking some driver may choose to defer unbind in some workqueue > etc. Doesn't really change anything, the lifetime of the PASID wouuld be the lifetime of the notifier and the bind, and DMA can't continue without the notifier registered. Jason
