Re: [PATCH v4 2/9] vfio-iommufd: Create iommufd_access for noiommu devices

Jason Gunthorpe
2023-05-03T19:42:01Z

> > My general idea to complete the no-iommu feature is to add a new IOCTL
> > to VFIO that is 'pin iova and return dma addr' that no-iommu userspace
> > would call instead of trying to abuse mlock and /proc/ to do it. That
> > ioctl would use the IOAS attached to the access just like a mdev would
> > do, so it has a real IOVA, but it is not a mdev.
>
> This new ioctl may be IOMMUFD ioctl since its input is the IOAS and
> addr, nothing related to the device. Is it?

No, definately a VFIO special ioctl for VFIO no-iommu mode.

> Sure. That's also why I added a noiommu test to avoid calling
> unmap callback although it seems not possible to have unmap
> callback as mdev drivers would implement it.

Just have a special noiommu ops and use an empty unmap function and
pass that to the special noiommu access creation.

Jason