On Mon, May 17, 2021 at 02:22:06PM +0200, Joerg Roedel wrote:

On Fri, May 14, 2021 at 10:31:43AM -0300, Jason Gunthorpe wrote:

quoted

There is no place for "domain as a carrier of PASID"
there. mdev_device should NOT participate in the IOMMU layer because
it is NOT a HW device. Trying to warp mdev_device into an IOMMU
presence is already the source of a lot of this hacky code.

Having the mdev abstraction is way better than making the IOMMU code
IOASID aware. The later requires either new parameters to existing
functions or new functions. With the mdev abstraction no new functions
are needed in the core API.

All that does it lock PASID to mdev which is not at all where this
needs to go.

Yes, I know, We have the AUX-domain specific functions now, but I
suggested a while back to turn the mdev code into its own bus
implementation and let the IOMMU driver deal with whether it has an mdev
or a pdev. When that is done the aux-specific functions can go away.

Yuk, no.

PASID is not connected to the driver model. It is inherently wrong to
suggest this. 

PASID is a property of a PCI device and any PCI device driver should
be able to spawn PASIDs without silly restrictions.

Fixing the IOMMU API is clearly needed here to get a clean PASID
implementation in the kernel.

quoted

IOASID represents the IOVA address space.

No, when it comes to the IOMMU-API, a domain represents an address
space.

Intel is building a new uAPI and here IOASID is the word they picked
to represent the IOVA address space. How it is mapped to the kernel is
TBD, I guess, but domain implies both more and less than a IOASID so it
isn't a 1:1 correspondence.

quoted

Two concepts that represent the same thing is not great :)

Agreed, so an IOASID should be an IOMMU-domain, if its not used for
passing an mm_struct to a device.

We aren't talking about mm_struct.

As above a domain isn't an IOASID, it only does a few things an IOASID
can do.

Jason

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