Re: (proposal) RE: [PATCH v7 00/16] vfio: expose virtual Shared Virtual Addressing to VMs

Jason Gunthorpe
2020-10-20T13:54:53Z

On Tue, Oct 20, 2020 at 09:40:14AM +0000, Liu, Yi L wrote:

> > See previous discussion with Kevin. If I understand correctly, you expect a shared
> > L2 table if vDPA and VFIO device are using the same PASID.
>
> L2 table sharing is not mandatory. The mapping is the same, but no need to
> assume L2 tables are shared. Especially for VFIO/vDPA devices. Even within
> a passthru framework, like VFIO, if the attributes of backend IOMMU are not
> the same, the L2 page table are not shared, but the mapping is the same.

I think not being able to share the PASID shows exactly why this VFIO
centric approach is bad.

Jason