Re: [Qemu-devel] [PATCH 2/3] exec: simplify address_space_get_iotlb_entry

[Paolo Bonzini]

On 05/06/2017 05:07, Peter Xu wrote:
> I don't sure whether it'll be a good interface for IOTLB. AFAIU at
> least for VT-d, the IOMMU translation is page aligned which is defined
> by spec, so it makes sense that (again at least for VT-d) here we'd
> better just use page_mask/addr_mask.
> 
> That's also how I know about IOMMU in general - I assume it do the
> translations always with page masks (never arbitary length), though
> page size can differ from platfrom to platform, that's why here the
> IOTLB interface used addr_mask, then it works for all platforms. I
> don't know whether I'm 100% correct here though.
> 
> Maybe David/Paolo/... would comment as well?

I would ask David.  There are PowerPC MMUs that allow fast lookup of
arbitrarily-sized windows (not necessarily power of two), so maybe the
IOMMUs can do the same.

Paolo