> From: Nicolin Chen <nicolinc@xxxxxxxxxx> > Sent: Wednesday, March 15, 2023 5:03 PM > > Hi, > > On Wed, Mar 15, 2023 at 06:50:53AM +0000, Tian, Kevin wrote: > > > > So, this preparatory series will add a pair of simple attach() > > > and detach() APIs. Then the cdev series will add the locking > > > and the ioas_unpin stuff as a rework of the detach() API. > > > > I think they can be something mingled... the sample code that > > > I sent previously could take care of those conditions. But, I > > > am also thinking a bit that maybe attach() does not need the > > > locking? I can do a separate replace() function in this case. > > > > > > > w/o locking then you need smp_store_release() and its pair. > > > > anyway it's not in perf critical path. Keeping lock for attach > > is simpler and safe. > > OK. Basically I followed what Jason suggested by having three > APIs and combined Kevin's inputs about the difference between > the attach/replace(). I also updated the replace changes, and > rebased all nesting (infrastructure, VT-d and SMMU): > https://github.com/nicolinc/iommufd/commits/wip/iommufd_nesting- > 03142023 > > The major three changes for those APIs: > [1] This adds iommufd_access_attach() in this series: > "iommufd: Create access in vfio_iommufd_emulated_bind()" > > https://github.com/nicolinc/iommufd/commit/34fba7509429380f828fb23dcc > a5ceaeb40e22b5 WARN_ON(!vdev->iommufd_access) in vfio_iommufd_emulated_attach_ioas() > [2] This adds iommufd_access_detach() in the cdev series: > "iommufd/device: Add iommufd_access_detach() API" > > https://github.com/nicolinc/iommufd/commit/4110522146ca1fc0d5321c04a > 097e2c9d9e26af4 also add a check if old_ioas exists it must equal to the new_ioas in attach. > [3] This adds iommufd_access_replace() in the replace series: > "iommufd: Add iommufd_access_replace() API" > > https://github.com/nicolinc/iommufd/commit/36507fa9f0f42cf1a5bebe7c9b > c2bf319b7654a8 lockdep_assert_held(&access->ioas_lock) in iommufd_access_change_pt() cur_ioas is uninitialized in iommufd_access_change_pt(). Actually we don't need an extra variable given only one reference to access->ioas. similarly directly refer to access->ioas in iommufd_access_replace(). > > Please check if they look okay, so that Yi can integrate them > accordingly to the emulated/cdev series. this split looks reasonable to me. Go ahead.
