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/34fba7509429380f828fb23dcca5ceaeb40e22b5 [2] This adds iommufd_access_detach() in the cdev series: "iommufd/device: Add iommufd_access_detach() API" https://github.com/nicolinc/iommufd/commit/4110522146ca1fc0d5321c04a097e2c9d9e26af4 [3] This adds iommufd_access_replace() in the replace series: "iommufd: Add iommufd_access_replace() API" https://github.com/nicolinc/iommufd/commit/36507fa9f0f42cf1a5bebe7c9bc2bf319b7654a8 Please check if they look okay, so that Yi can integrate them accordingly to the emulated/cdev series. [*] This is the patch that I posted in the other mail addressing Kevin's comments on iommufd_ctx_get(): "iommufd/device: Do iommufd_ctx_get() at the top of iommufd_access_create()" https://github.com/nicolinc/iommufd/commit/077b09bb83329dc046753f4ef672f5bf6386755c (I just saw Yi's reply concerning its necessity. Feel free to drop in that case.) Thanks Nicolin P.S. Attaching the list of changes with their locations: 3791dedf98e8 cover-letter: Add IO page table replacement support c8ebf51c3c9b vfio: Support IO page table replacement c5710f23e8f6 iommufd/selftest: Add IOMMU_TEST_OP_ACCESS_REPLACE_IOAS coverage [3] 36507fa9f0f4 iommufd: Add iommufd_access_replace() API 0263855d1e8b vfio: Do not allow !ops->dma_unmap in vfio_pin/unpin_pages() e39ed55e77a0 cover-letter: Add vfio_device cdev for iommufd support 26fd7fccaef3 docs: vfio: Add vfio device cdev description f10f3e3162bb vfio: Compile group optionally 9588ae4c4049 vfio: Add VFIO_DEVICE_AT[DE]TACH_IOMMUFD_PT 3e57108eac64 vfio: Add VFIO_DEVICE_BIND_IOMMUFD b925716dd226 vfio: Add cdev for vfio_device db309463ab92 vfio-iommufd: Add detach_ioas support for emulated VFIO devices [2] 4110522146ca iommufd/device: Add iommufd_access_detach() API abca7e1e063a vfio-iommufd: Add detach_ioas support for physical VFIO devices 9d368f7247c7 vfio: Record devid in vfio_device_file 683af0a471e1 vfio-iommufd: Split the compat_ioas attach out from vfio_iommufd_bind() 32a2e7de1d53 vfio-iommufd: Split the no-iommu support out from vfio_iommufd_bind() 8a1c042379f5 vfio: Make vfio_device_first_open() to accept NULL iommufd for noiommu fc6e0ed2aa44 vfio: Make vfio_device_open() single open for device cdev path 3f6821d507a4 vfio: Add cdev_device_open_cnt to vfio_group 896cde40a016 vfio: Block device access via device fd until device is opened f422c4216a19 vfio: Pass struct vfio_device_file * to vfio_device_open/close() b187f9980fed kvm/vfio: Accept vfio device file from userspace 721e2e60ff54 kvm/vfio: Rename kvm_vfio_group to prepare for accepting vfio device fd 8993c4c75c20 vfio: Accept vfio device file in the KVM facing kAPI a92c45ae0ce6 vfio: Remove vfio_file_is_group() fb586f783934 vfio: Refine vfio file kAPIs for KVM 50694af6f3c0 vfio: Allocate per device file structure df21c0737eef cover-letter: Make vfio-pci hot reset prepared for vfio device cdev 5c25c874d7e0 vfio/pci: Accept device fd in VFIO_DEVICE_PCI_HOT_RESET ioctl 7c30ce8b54db vfio: Accpet device file from vfio PCI hot reset path e3209342db44 vfio: Refine vfio file kAPIs for vfio PCI hot reset 8354fd79944e vfio/pci: Rename the helpers and data in hot reset path to accept device fd 54387efb858c vfio/pci: Allow passing zero-length fd array in VFIO_DEVICE_PCI_HOT_RESET cd93ffb62c51 vfio/pci: Only need to check opened devices in the dev_set for hot reset 2a6fd7231cbf vfio/pci: Update comment around group_fd get in vfio_pci_ioctl_pci_hot_reset() 480abea5961e cover-letter: vfio: Make emulated devices prepared for vfio device cdev 46b6d1ae1754 vfio: Check the presence for iommufd callbacks in __vfio_register_dev() 6064b9f81817 Samples/mdev: Uses the vfio emulated iommufd ops set in the mdev sample drivers c20852af7291 vfio-iommufd: Make vfio_iommufd_emulated_bind() return iommufd_access ID 3405865b0b3f vfio-iommufd: No need to record iommufd_ctx in vfio_device [*] 077b09bb8332 iommufd/device: Do iommufd_ctx_get() at the top of iommufd_access_create() [1] 34fba7509429 iommufd: Create access in vfio_iommufd_emulated_bind() a5d8ac47554f docs: kvm: vfio: Require call KVM_DEV_VFIO_GROUP_ADD before VFIO_GROUP_GET_DEVICE_FD
