map user space memory as gart memory for intel integrated graphics chip

[Alan Cox]

On Iau, 2005-12-08 at 19:52 +0800, Austin Yuan wrote:
> buffer. Because the interface of "alloc_by_type" only receives a
> simple parameter "type", here I hide the user space address into
> "type" and re-get it in alloc_userspace_memory.

That should probably be fixed by extending the API to pass both

> I use this interface to easily implement XAA readpixmap/imagewrite
> driver interfaces, and get a better performance. Here, I didn't attach
> the patch for i810 driver. I just want to get some comments about it,
> and if you think it makes sense, I'd like to make it more generic.
> 
> Any comments are appreciated, thanks.


The one thing I don't understand looking at this is that I understood
AGP pages should be marked uncached. However user space pages may exist
in many mappings and the CPU also requires all mappings of a page are
consistent.

Does i8xx need the page uncached or is it enough to wbinvd the pages in
question on writing and invalidate them before reading, or does the i8xx
in fact take full part in the cache coherency ?