Re: [PATCH RFC 21/26] dma-buf: Add the Physical Address List DMA mapping type

[Xu Yilun <yilun.xu@linux.intel.com>]

> Would you be open to an in-between? The exporter and importer both
> have information that should not leak into each other's drivers. 
> 
> What if the dmabuf mapping type core code was the only thing that had
> access to *BOTH*? The exporter provides the address data, the importer
> provides the iommu_domain. The core code, and only the core code, has
> both and does the required operation?

I think that may not work for KVM. On IOMMU side, IOMMUFD acts as the
address space (iova) manager and dma_api/IOMMU driver acts as the
actual page table mapper. But for KVM, it is both. KVM doesn't allow
another component to provide an unknown address space (GPA space) and
say "map it", so doesn't expose to other components about "KVM domain".

Even if we expose "KVM domain", KVM still acts as the importer and the
mapper, is it wierd to say we trust KVM-the-mapper, but don't trust
KVM-the-as-manager?

Is it also wierd that we trust IOMMU-the-mapper, but don't trust
IOMMUFD-the-as-manager? There are more IOMMU drivers than IOMMUFD...