On Mon, 13 Feb 2023 07:13:33 -0800 Yi Liu <yi.l.liu@xxxxxxxxx> 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 prerequisite for 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_v3 > (config CONFIG_IOMMUFD=y CONFIG_VFIO_DEVICE_CDEV=y) Even using your branch[1], it seems like this has not been tested except with cdev support enabled: /home/alwillia/Work/linux.git/drivers/vfio/vfio_main.c: In function ‘vfio_device_add’: /home/alwillia/Work/linux.git/drivers/vfio/vfio_main.c:253:48: error: ‘struct vfio_device’ has no member named ‘cdev’; did you mean ‘dev’? 253 | ret = cdev_device_add(&device->cdev, &device->device); | ^~~~ | dev /home/alwillia/Work/linux.git/drivers/vfio/vfio_main.c: In function ‘vfio_device_del’: /home/alwillia/Work/linux.git/drivers/vfio/vfio_main.c:262:42: error: ‘struct vfio_device’ has no member named ‘cdev’; did you mean ‘dev’? 262 | cdev_device_del(&device->cdev, &device->device); | ^~~~ | dev Additionally the VFIO_ENABLE_GROUP Kconfig option doesn't make much sense to me, it seems entirely redundant to VFIO_GROUP. I think it's too late for v6.3 already, but given this needs at least one more spin, let's set expectations of this being v6.4 material. Thanks, Alex [1] 98491da60ae1 cover-letter: Add vfio_device cdev for iommufd support
