[Intel-gfx] pin OABUFFER to GGTT

[Mateo Lozano, Oscar]

Submitting again (this time copying the mailing list correctly):

The bo_pin ioctl has been discarded in GEN6+ with this patch:

    drm/i915: Reject the pin ioctl on gen6+
    
    Especially with ppgtt this kinda stopped making sense. And if we
    indeed need this to hack around an issue, we need something that also
    works for non-root.
    
    Signed-off-by: Daniel Vetter daniel.vetter at ffwll.ch

The thing is, the performance team used this call to pin the OABUFFER to GGTT and then mapping it to userspace. This OABUFFER cannot be in PPGTT because: "When each context has its own Per Process GTT, this field should be always set to GGTT." (BSpec dixit).

Can we re-enable it? or should we find an alternative for this case?

-- Oscar