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

From: Michael S. Tsirkin
Date: Mon Jun 04 2018 - 12:34:27 EST

On Mon, Jun 04, 2018 at 11:14:36PM +1000, Benjamin Herrenschmidt wrote:
> On Mon, 2018-06-04 at 05:55 -0700, Christoph Hellwig wrote:
> > On Mon, Jun 04, 2018 at 03:43:09PM +0300, Michael S. Tsirkin wrote:
> > > Another is that given the basic functionality is in there, optimizations
> > > can possibly wait until per-device quirks in DMA API are supported.
> >
> > We have had per-device dma_ops for quite a while.
> I've asked Ansuman to start with a patch that converts virtio to use
> DMA ops always, along with an init quirk to hookup "direct" ops when
> the IOMMU flag isn't set.
> This will at least remove that horrid duplication of code path we have
> in there.
> Then we can just involve the arch in that init quirk so we can chose an
> alternate set of ops when running a secure VM.
> This is completely orthogonal to whether an iommu exist qemu side or
> not, and should be entirely solved on the Linux side.
> Cheers,
> Ben.

Sounds good to me.