[Xen-devel] [PATCH, RFC 0/7] IOMMU: add phantom function support

["Jan Beulich" <JBeulich@xxxxxxxx>]

While I'm unaware of devices making use of this functionality in
proper ways, the goal of this patch set is to leverage the enabling
of the specified behavior as a workaround for devices that behave
as if they made use of this functionality _without_ advertising so
in the PCIe capability structure.

While it would have been possible to leave the generic IOMMU
code untouched, and deal with the creation of the necessary
device context entries in the individual IOMMUs' implementations,
I felt that it was cleaner to have as much of the necessary
abstraction in the generic layer.

The adjustments in particular imply that for the relevant
operations, (PCI-dev, devfn) tuples get passed, with the PCI
device referring to the real device and devfn representing
either the real device or the phantom function. Consequently,
for any operation intended to deal with the real device, the
devfn of the device itself must be used, whereas for anything
targeting the phantom function the passed in value is the
correct one to pass on.

1: IOMMU: adjust (re)assign operation parameters
2: IOMMU: adjust add/remove operation parameters
3: VT-d: adjust context map/unmap parameters
4: AMD IOMMU: adjust flush function parameters
5: IOMMU: consolidate pdev_type() and cache its result for a given device
6: IOMMU: add phantom function support
7: IOMMU: add option to specify devices behaving like ones using phantom 
functions

As the patch set wasn't tested on the affected systems yet, I'm
intentionally not adding S-o-b tags yet. I would appreciate review
nevertheless (and even more so, given that I won't be able to
test this code other than what I did in contrived scenarios).

Jan


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