On 2022/12/19 16:47, Yi Liu wrote:
Existing VFIO provides group-centric user APIs for userspace. Userspace opens the /dev/vfio/$group_id first before getting device fd and hence getting access to device. This is not the desired model for iommufd. Per the conclusion of community discussion[1], iommufd provides device-centric kAPIs and requires its consumer (like VFIO) to be device-centric user APIs. Such user APIs are used to associate device with iommufd and also the I/O address spaces managed by the iommufd. This series first introduces a per device file structure to be prepared for further enhancement and refactors the kvm-vfio code to be prepared for accepting device file from userspace. Then refactors the vfio to be able to handle iommufd binding. This refactor includes the mechanism of blocking device access before iommufd bind, making vfio_device_open() be exclusive between the group path and the cdev path. Eventually, adds the cdev support for vfio device, and makes group infrastructure optional as it is not needed when vfio device cdev is compiled. This is also a base for further support iommu nesting for vfio device[2]. The complete code can be found in below branch, simple test done with the legacy group path and the cdev path. Draft QEMU branch can be found at[3] https://github.com/yiliu1765/iommufd/tree/vfio_device_cdev_rfcv1 (config CONFIG_IOMMUFD=y) [1] https://lore.kernel.org/kvm/BN9PR11MB5433B1E4AE5B0480369F97178C189@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx/ [2] https://github.com/yiliu1765/iommufd/tree/wip/iommufd-v6.1-rc3-nesting [3] https://github.com/yiliu1765/qemu/tree/wip/qemu-iommufd-6.1-rc3
this is targeting for 6.3. So would appreciate early comments if bandwidth allows. Otherwise, I can wait after merge window. :-) -- Thanks, Yi Liu
