[Intel-gfx] [PATCH v5 17/19] vfio: Add VFIO_DEVICE_AT[DE]TACH_IOMMUFD_PT

[Jason Gunthorpe]

On Tue, Feb 28, 2023 at 02:51:28AM +0000, Liu, Yi L wrote:
> > This seems strange. no iommu mode should have a NULL dev->iommufctx.
> > Why do we have a df->noiommu at all?
> 
> This is due to the vfio_device_first_open(). Detail as below comment (part of
> patch 0016).
> 
> +	/*
> +	 * For group/container path, iommufd pointer is NULL when comes
> +	 * into this helper. Its noiommu support is handled by
> +	 * vfio_device_group_use_iommu()
> +	 *
> +	 * For iommufd compat mode, iommufd pointer here is a valid value.
> +	 * Its noiommu support is in vfio_iommufd_bind().
> +	 *
> +	 * For device cdev path, iommufd pointer here is a valid value for
> +	 * normal cases, but it is NULL if it's noiommu. Check df->noiommu
> +	 * to differentiate cdev noiommu from the group/container path which
> +	 * also passes NULL iommufd pointer in. If set then do nothing.
> +	 */

If the group is in iommufd mode then it should set this pointer too.

Jason