Re: [RFC v2 8/8] iommu/arm-smmu: implement add_reserved_regions callback

[Joerg Roedel]

Hi Eric,

On Fri, Nov 11, 2016 at 04:47:01PM +0100, Auger Eric wrote:
> Effectively in passthrough use case, the userspace defines the address
> space layout and maps guest RAM PA=IOVA to PAs (using
> VFIO_IOMMU_MAP_DMA). But this address space does not comprise the MSI
> IOVAs. Userspace does not care about MSI IOMMU mapping. So the MSI IOVA
> region must be allocated by either the VFIO driver or the IOMMU driver I
> think. Who else could initialize the IOVA allocator domain?

So I think we need a way to tell userspace about the reserved regions
(per iommu-group) so that userspace knows where it can not map anything,
and VFIO can enforce that. But the right struct here is not an
iova-allocator rb-tree, a ordered linked list should be sufficient.


	Joerg