Re: [Xen-devel] [PATCH 6/7] vtd: change lookup_page failure semantics

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Paul Durrant [mailto:paul.durrant@xxxxxxxxxx]
> Sent: Thursday, September 20, 2018 10:12 PM
> 
> Commit 43d1622b "vtd: add lookup_page method to iommu_ops" added a
> lookup method in to the VT-d IOMMU implementation. In some cases (such
> as
> when shared EPT is in operation) that function simply passes back an
> identity MFN (i.e. an MFN with the same value as the DFN that was passed
> in), but this doesn't actually make a lot of sense. If, for instance,
> shared EPT is used then really the function should be doing a P2M lookup
> since DFN space will be identical to GFN space.
> 
> In practice there are no current callers of the lookup_page method and,
> when PV-IOMMU support is added, the method will not be called if either
> shared EPT is in operation or iommu_passthrough is set, so this patch
> simply fails the method with -EOPNOTSUPP in those cases.
> 
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>

Acked-by: Kevin Tian <kevin.tian@xxxxxxxxx>

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