[bug report] drm/ttm: add transparent huge page support for DMA allocations v2

[Koenig, Christian]

Am 27.06.19 um 18:55 schrieb Christoph Hellwig:
> On Thu, Jun 27, 2019 at 04:19:14PM +0000, Koenig, Christian wrote:
>> If not then the real question is how to correctly get the backing page
>> from dma_alloc_attrs().
> The answer to that is that you can't.  dma_alloc_* is an opaque
> allocator that only gives you a kernel virtual address and a dma_addr_t,
> and you can't poke into the internals, as there are a variety of
> different implementations.

Thought that you would say that. It basically confirms my suspicion that 
the whole TTM page allocation code is not really working that well.

How do we then do things like mapping that memory to userspace?

And how to we control caching, write combine/back of that memory?

Christian.