On 2 May 2018 at 10:25, Paolo Bonzini <pbonz...@redhat.com> wrote: > On 01/05/2018 10:59, Peter Maydell wrote: >> As well as the SMMU, I'm also thinking about using the IOMMU >> infrastructure for the v8M Memory Protection Controller >> (though that is a bit trickier as I also need it to support >> TCG execution in an IOMMU-controlled region, which is an >> orthogonal bit of work to attribute support).
> This is going to conflict with the MemoryRegionCache patches (review > welcome :)), as they add a new function address_space_translate_iommu. > But apart from this it seems like a no brainer. (We talked about this on IRC, but I don't really have any good ideas about the API changes needed, so I figured I'd write it up here.) While working through this and the MPC changes, I realized that if we pass transaction attributes through to the IOMMU translate method then we also need to change the API of the IOMMU notifier system. This is because a txattrs-aware IOMMU might return more than one mapping for a particular input address (eg "use mapping A if txattrs.secure, but mapping B if not"). So map/unmap events become more complex than just "unmap for address X" and "map for address X" -- you need to distinguish "here's the new map for address X with txattrs XA". Presumably we also want a way for notifier users like vfio to detect "I'm dealing with an IOMMU that is txattrs aware in a way I can't deal with" so they can usefully bail out rather than not working. Unfortunately I don't really know enough about our two current users of notifiers (vhost and vfio) to know what they actually need the iommu notifications for... (For the notifier I need to add for TCG, the requirements are easy: I just want to be able to get unmap events so I can flush the TCG TLB when the info I've cached from translate calls is stale.) thanks -- PMM
