On Wed, Apr 08, 2020 at 04:04:25PM +0200, Jean-Philippe Brucker wrote: > The IOMMU SVA API currently requires device drivers to implement an > mm_exit() callback, which stops device jobs that do DMA. This function > is called in the release() MMU notifier, when an address space that is > shared with a device exits. > > It has been noted several time during discussions about SVA that > cancelling DMA jobs can be slow and complex, and doing it in the > release() notifier might cause synchronization issues (patch 2 has more > background). Device drivers must in any case call unbind() to remove > their bond, after stopping DMA from a more favorable context (release of > a file descriptor). > > So after mm exits, rather than notifying device drivers, we can hold on > to the PASID until unbind(), ask IOMMU drivers to silently abort DMA and > Page Requests in the meantime. This change should relieve the mmput() > path. At least all the patch comments look like they are on the right track to me, thanks for doing this. Jason
