Re: [PATCH v3 11/11] iommufd: Allow iommufd to supply /dev/vfio/vfio

[Jason Gunthorpe <jgg@nvidia.com>]

On Thu, Nov 17, 2022 at 01:34:17PM -0700, Alex Williamson wrote:
> > +config IOMMUFD_VFIO_CONTAINER
> > +	bool "IOMMUFD provides the VFIO container /dev/vfio/vfio"
> > +	depends on VFIO && !VFIO_CONTAINER
> > +	default VFIO && !VFIO_CONTAINER
> > +	help
> > +	  IOMMUFD will provide /dev/vfio/vfio instead of VFIO. This relies on
> > +	  IOMMUFD providing compatibility emulation to give the same ioctls.
> > +	  It provides an option to build a kernel with legacy VFIO components
> > +	  removed.
> > +
> > +	  Unless testing IOMMUFD say N here.
> > +
> 
> "Unless testing..." alone is a bit more subtle that I thought we were
> discussing.  I was expecting something more like:
> 
>   IOMMUFD VFIO container emulation is known to lack certain features of
>   the native VFIO container, such as no-IOMMU support, peer-to-peer DMA
>   mapping, PPC IOMMU support, as well as other potentially undiscovered
>   gaps.  This option is currently intended for the purpose of testing
>   IOMMUFD with unmodified userspace supporting VFIO and making use of
>   the Type1 VFIO IOMMU backend.  General purpose enabling of this
>   option is currently discouraged.
> 
>   Unless testing IOMMUFD, say N here.

Done, thanks

Jason