On Fri, Jun 26, 2020 at 02:22:41PM +0200, Björn Töpel wrote:

Thanks for clarifying that. Let's work on a solution that can reside in
the dma mapping core.

quoted

The commit seems to have a long dove tail of commits depending on it
despite only being a month old, so maybe you can do the revert for now?

Reverting the whole series sounds a bit too much. Let's focus on the
part that breaks the dma api abstraction. I'm assuming that you're
referring to the

  static bool xp_check_cheap_dma(struct xsk_buff_pool *pool)

function (and related functions called from that)?

Yes.

quoted

Note that this is somewhat urgent, as various of the APIs that the code
is abusing are slated to go away for Linux 5.9, so this addition comes
at a really bad time.

Understood. Wdyt about something in the lines of the diff below? It's
build tested only, but removes all non-dma API usage ("poking
internals"). Would that be a way forward, and then as a next step work
on a solution that would give similar benefits, but something that would
live in the dma mapping core?

Yes, that would solve the immediate issues.