Re: [PATCH v2 3/4] iommufd: Destroy vdevice on idevice destroy

[Baolu Lu <baolu.lu@linux.intel.com>]

On 6/23/25 17:49, Xu Yilun wrote:
> Destroy iommufd_vdevice(vdev) on iommufd_idevice(idev) destroy so that
> vdev can't outlive idev.
> 
> iommufd_device(idev) represents the physical device bound to iommufd,
> while the iommufd_vdevice(vdev) represents the virtual instance of the
> physical device in the VM. The lifecycle of the vdev should not be
> longer than idev. This doesn't cause real problem on existing use cases
> cause vdev doesn't impact the physical device, only provides
> virtualization information. But to extend vdev for Confidential
> Computing(CC), there are needs to do secure configuration for the vdev,
> e.g. TSM Bind/Unbind. These configurations should be rolled back on idev
> destroy, or the external driver(VFIO) functionality may be impact.
> 
> Building the association between idev & vdev requires the two objects
> pointing each other, but not referencing each other.

Does this mean each idevice can have at most a single vdevice? Is it
possible that different PASIDs of a physical device are assigned to
userspace for different purposes, such that there is a need for multiple
vdevices per idevice?

Thanks,
baolu