On Sat, Feb 22, 2020 at 02:07:58PM -0500, Michael S. Tsirkin wrote:

On Fri, Feb 21, 2020 at 03:33:40PM +0100, Halil Pasic wrote:

quoted

AFAIU you have a positive attitude towards the idea, that 
!F_VIRTIO_PLATFORM implies 'no DMA API is used by virtio' 
should be scrapped. 

I would like to accomplish that without adverse effects to virtio-ccw
(because caring for virtio-ccw is a part of job description).

Regards,
Halil

It is possible, in theory. IIRC the main challenge is that DMA API
has overhead of indirect function calls even when all it
does it return back the PA without changes.

That overhead is gone now, the DMA direct calls are direct calls these
days.