Re: [RFC V2] virtio: Add platform specific DMA API translation for virito devices

From: Christoph Hellwig
Date: Fri Jun 15 2018 - 05:16:37 EST

On Wed, Jun 13, 2018 at 11:11:01PM +1000, Benjamin Herrenschmidt wrote:
> Actually ... the stuff in lib/dma-direct.c seems to be just it, no ?
> There's no cache flushing and there's no architecture hooks that I can
> see other than the AMD security stuff which is probably fine.
> Or am I missing something ?

You are missing the __phys_to_dma arch hook that allows architectures
to adjust the dma address. Various systems have offsets, or even
multiple banks with different offsets there. Most of them don't
use the dma-direct code yet (working on it), but there are a few
examples in the tree already.