Re: [PATCH 06/10] vfio-iommufd: Allow iommufd to be used in place of a container fd

[Jason Gunthorpe <jgg@nvidia.com>]

On Wed, Nov 02, 2022 at 03:28:20PM +0800, Yi Liu wrote:
> On 2022/10/26 02:50, Jason Gunthorpe wrote:
> > This makes VFIO_GROUP_SET_CONTAINER accept both a vfio container FD and an
> > iommufd.
> > 
> > In iommufd mode an IOAS will exist after the SET_CONTAINER, but it will
> > not be attached to any groups.
> 
> is there any special reason that we cannot attach the IOAS in the SET
> container phase or SET_IOMMU phase?

It is because iommufd has been deliberately made to work only on
struct device * not iommu_groups, and when we go to do the
SET_CONTAINER we have no idea what the device will be.

So defering the operation is the cleanest approach.

> >  From a VFIO perspective this means that the VFIO_GROUP_GET_STATUS and
> > VFIO_GROUP_FLAGS_VIABLE works subtly differently. With the container FD
> > the iommu_group_claim_dma_owner() is done during SET_CONTAINER but for
> > IOMMFD this is done during VFIO_GROUP_GET_DEVICE_FD. Meaning that
> 
> s/IOMMFD/IOMMUFD

Done

Jason