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

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