GEM allocation for para-virtualized DRM driver

[Rob Clark]

On Fri, Mar 17, 2017 at 1:39 PM, Oleksandr Andrushchenko
<andr2000 at gmail.com> wrote:
> Hello,
> I am writing a para-virtualized DRM driver for Xen hypervisor
> and it now works with DRM CMA helpers, but I would also like
> to make it work with non-contigous memory: virtual machine
> that the driver runs in can't guarantee that CMA is actually
> physically contigous (that is not a problem because of IPMMU
> and other means, the only constraint I have is that I cannot mmap
> with pgprot == noncached). So, I am planning to use *drm_gem_get_pages* +
> *shmem_read_mapping_page_gfp* to allocate memory for GEM objects
> (scanout buffers + dma-bufs shared with virtual GPU)
>
> Do you think this is the right approach to take?

I guess if you had some case where you needed to "migrate" buffers
between host and guest memory, then TTM might be useful.  Otherwise
this sounds like the right approach.

BR,
-R