Re: [PATCH v2 17/18] drm/i915: Wa32bitGeneralStateOffset & Wa32bitInstructionBaseOffset

Chris Wilson
2015-06-17T12:53:22Z

On Wed, Jun 17, 2015 at 02:49:47PM +0200, Daniel Vetter wrote:
> On Wed, Jun 10, 2015 at 07:09:03PM +0100, Chris Wilson wrote:
> > On Wed, Jun 10, 2015 at 05:46:54PM +0100, Michel Thierry wrote:
> > > There are some allocations that must be only referenced by 32bit
> > > offsets. To limit the chances of having the first 4GB already full,
> > > objects not requiring this workaround use DRM_MM_SEARCH_BELOW/
> > > DRM_MM_CREATE_TOP flags
> > >
> > > User must pass I915_EXEC_SUPPORTS_48BADDRESS flag to indicate it can
> > > be allocated above the 32b address range.
> >
> > This should be a per-object flag not per-execbuffer.
>
> We need both. This one to opt into the large address space, the per-object
> one to apply the w/a. Also libdrm/mesa patches for this are still missing.

Do we need the opt in on the context? The 48bit vm is lazily
constructed, if no object asks to use the high range, it will never be
populated. Or is there a cost with preparing a 48bit vm?
-Chris

--
Chris Wilson, Intel Open Source Technology Centre