Re: [RFC PATCH] virtio_ring: Use DMA API if guest memory is encrypted

[Christoph Hellwig]

On Sat, Aug 10, 2019 at 11:46:21PM -0700, Ram Pai wrote:
> If the hypervisor (hardware for hw virtio devices) does not mandate a
> DMA API, why is it illegal for the driver to request, special handling
> of its i/o buffers? Why are we associating this special handling to
> always mean, some DMA address translation? Can't there be 
> any other kind of special handling needs, that has nothing to do with
> DMA address translation?

I don't think it is illegal per se.  It is however completely broken
if we do that decision on a system weide scale rather than properly
requesting it through a per-device flag in the normal virtio framework.