> From: Nicolin Chen <nicolinc@xxxxxxxxxx> > Sent: Thursday, February 2, 2023 3:05 PM > > Support an access->ioas replacement in iommufd_access_set_ioas(), which > sets the access->ioas to NULL provisionally so that any further incoming > iommufd_access_pin_pages() callback can be blocked. > > Then, call access->ops->unmap() to clean up the entire iopt. To allow an > iommufd_access_unpin_pages() callback to happen via this unmap() call, > add an ioas_unpin pointer so the unpin routine won't be affected by the > "access->ioas = NULL" trick above. > > Also, a vdev without an ops->dma_unmap implementation cannot replace its > access->ioas pointer. So add an iommufd_access_ioas_is_attached() helper > to sanity that. > Presumably a driver which doesn't implement ops->dma_unmap shouldn't be allowed to do pin/unpin. But it could use vfio_dma_rw() to access an iova range. In the latter case I don't see why replace cannot work. Probably what's required here is to deny !ops->dma_unmap in vfio_pin/unpin_pages then making here replace always allowed?
