On Fri, Jun 02, 2023 at 05:16:29AM -0700, 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. After this, adds a mechanism for > blocking device access before iommufd bind. Then refactors the vfio to be > able to handle cdev path (e.g. iommufd binding, no-iommufd, [de]attach ioas). > This refactor includes making the device_open exclusive between the group > and the cdev path, only allow single device open in cdev path; vfio-iommufd > code is also refactored to support cdev. e.g. split the vfio_iommufd_bind() > into two steps. Eventually, adds the cdev support for vfio device and the > new ioctls, then makes group infrastructure optional as it is not needed > when vfio device cdev is compiled. > > This series is based on some preparation works done to vfio emulated devices[2] > and vfio pci hot reset enhancements[3]. > > This series is a prerequisite for iommu nesting for vfio device[4] [5]. > > The complete code can be found in below branch, simple tests done to the > legacy group path and the cdev path. Draft QEMU branch can be found at[6] > However, the noiommu mode test is only done with some hacks in kernel and > qemu to check if qemu can boot with noiommu devices. > > https://github.com/yiliu1765/iommufd/tree/vfio_device_cdev_v12 > (config CONFIG_IOMMUFD=y CONFIG_VFIO_DEVICE_CDEV=y) Rebased our nesting branch, and tested with an updated QEMU branch on ARM64 (SMMUv3): https://github.com/nicolinc/iommufd/commits/wip/iommufd_nesting-06052023-cdev-v12-nic https://github.com/nicolinc/qemu/commits/wip/iommufd_nesting-06062023 Tested-by: Nicolin Chen <nicolinc@xxxxxxxxxx> Thanks Nicolin
