[PATCH 3/6] vfio: remove the unused mdev iommu hook

[Jason Gunthorpe]

On Thu, May 13, 2021 at 03:28:52AM +0000, Tian, Kevin wrote:

> Are you specially concerned about this iommu_device hack which 
> directly connects mdev_device to iommu layer or the entire removed
> logic including the aux domain concept? For the former we are now 
> following up the referred thread to find a clean way. But for the latter 
> we feel it's still necessary regardless of how iommu interface is redesigned 
> to support device connection from the upper level driver. The reason is 
> that with mdev or subdevice one physical device could be attached to 
> multiple domains now. there could be a primary domain with DOMAIN_
> DMA type for DMA_API use by parent driver itself, and multiple auxiliary 
> domains with DOMAIN_UNMANAGED types for subdevices assigned to 
> different VMs.

Why do we need more domains than just the physical domain for the
parent? How does auxdomain appear in /dev/ioasid?

I never understood what this dead code was supposed to be used for.

Jason