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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 28.11.12 at 10:41, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:
> 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).

One open question (that I realized only after sending the batch)
is whether for such devices the source ID verification should be
set up using one of the SQ_13_IGNORE_* (fitting the stride).

Jan


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