Hi Baolu, On Thursday, August 29, 2019 3:43:31 AM CEST Lu Baolu wrote: > Hi Janusz, > > On 8/28/19 10:17 PM, Janusz Krzysztofik wrote: > >> We should avoid kernel panic when a intel_unmap() is called against > >> a non-existent domain. > > Does that mean you suggest to replace > > BUG_ON(!domain); > > with something like > > if (WARN_ON(!domain)) > > return; > > and to not care of orphaned mappings left allocated? Is there a way to inform > > users that their active DMA mappings are no longer valid and they shouldn't > > call dma_unmap_*()? > > > >> But we shouldn't expect the IOMMU driver not > >> cleaning up the domain info when a device remove notification comes and > >> wait until all file descriptors being closed, right? > > Shouldn't then the IOMMU driver take care of cleaning up resources still > > allocated on device remove before it invalidates and forgets their pointers? > > > > You are right. We need to wait until all allocated resources (iova and > mappings) to be released. > > How about registering a callback for BUS_NOTIFY_UNBOUND_DRIVER, and > removing the domain info when the driver detachment completes?
Device core calls BUS_NOTIFY_UNBOUND_DRIVER on each driver unbind, regardless of a device being removed or not. As long as the device is not unplugged and the BUS_NOTIFY_REMOVED_DEVICE notification not generated, an unbound driver is not a problem here. Morever, BUS_NOTIFY_UNBOUND_DRIVER is called even before BUS_NOTIFY_REMOVED_DEVICE so that wouldn't help anyway. Last but not least, bus events are independent of the IOMMU driver use via DMA-API it exposes. If keeping data for unplugged devices and reusing it on device re-plug is not acceptable then maybe the IOMMU driver should perform reference counting of its internal resources occupied by DMA-API users and perform cleanups on last release? Thanks, Janusz > > Thanks, > > Janusz > > Best regards, > Baolu > _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
