RE: [PATCH v5 00/19] Add vfio_device cdev for iommufd support

Liu, Yi L
2023-02-28T03:03:36Z

> From: Jason Gunthorpe <jgg@nvidia.com>
> Sent: Tuesday, February 28, 2023 3:21 AM
>
> On Mon, Feb 27, 2023 at 03:11:16AM -0800, 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 the device_open
> 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_v5
> > (config CONFIG_IOMMUFD=y CONFIG_VFIO_DEVICE_CDEV=y)
> >
> > base-commit: 63777bd2daa3625da6eada88bd9081f047664dad
>
> This needs to be rebased onto a clean v6.3-rc1 when it comes out

Yes, I'll send rebase and send one more version when v6.3-rc1
comes. Here just try to be near to the vfio code in Alex's next
branch.

Regards,
Yi Liu