[Intel-gfx] [PATCH 11/17] drm/i915/gtt: Lazily allocate page directories for gen7

[Joonas Lahtinen]

Quoting Chris Wilson (2018-06-10 22:43:19)
> As we were only supporting aliasing_ppgtt on gen7 for some time, we
> saved a few checks by preallocating the page directories on creation.
> However, since we need 2MiB of page directories for each ppgtt, to
> support arbitrary numbers of user contexts, we need to be more prudent
> in our allocations, and defer the page allocation until it is used. We
> don't recover unused pages yet as we found that doing so on the fly
> (i.e. altering TLB entries) would confuse the GPU.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> Cc: Matthew Auld <matthew.william.auld at gmail.com>
> Reviewed-by: Matthew Auld <matthew.william.auld at gmail.com>

Reviewed-by: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>

Regards, Joonas