[Intel-gfx] [PATCH] drm/i915: Deny wrapping an userptr into a framebuffer

[Daniel Vetter]

On Thu, Oct 22, 2015 at 04:23:09PM -0700, Kristian Høgsberg wrote:
> On Tue, Oct 13, 2015 at 6:22 AM, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> > Pinning a userptr onto the hardware raises interesting questions about
> > the lifetime of such a surface as the framebuffer extends that life
> > beyond the client's address space. That is the hardware will need to
> > keep scanning out from the backing storage even after the client wants
> > to remap its address space. As the hardware pins the backing storage,
> > the userptr becomes invalid and this raises a WARN when the clients
> > tries to unmap its address space. The situation can be even more
> > complicated when the buffer is passed between processes, between a
> > client and display server, where the lifetime and hardware access is
> > even more confusing. Deny it.
> 
> Can we allow this for unsynchronized userptrs?

I'd like to not add more complexity to a root-only feature.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch