Re: [PATCH] drm/virtio: fix mmap page attributes

[Gerd Hoffmann]

  Hi,

> There's similar code in udl, [1] which still uses writecombine for
> imported buffers. Virtio does not need this?

virtio doesn't support dma-buf imports (yet).
So no worries for now.

Why pick writecombine for the imported buffer btw?
It'll probably be correct for the majority of imports, but it still
looks like a educated guess to me.  What if you import from vgem?

I guess we should either ...
  (1) Ask the exporting driver to handle things, simliar to how it is
      done for vmaps already, probably by calling dma_buf_mmap(), or
  (2) Refuse to mmap imported objects via drm api.

> Aside from this, do you think we could handle all special cases within
> shmem?

Probably makes sense to teach shmem helpers about caching.

cheers,
  Gerd