[Intel-gfx] [PATCH] drm/i915: don't do allocate_va_range again on pin update

[Chris Wilson]

On Fri, May 12, 2017 at 10:14:23AM +0100, Chris Wilson wrote:
> From: Matthew Auld <matthew.auld at intel.com>
> 
> If a vma is already bound to a ppgtt, we incorrectly call
> allocate_va_range again when doing a PIN_UPDATE, which will result in
> over accounting within our paging structures, such that when we do
> unbind something we don't actually destroy the structures and end up
> inadvertently recycling them. In reality this probably isn't too bad,
> but once we start touching PDEs and PDPEs for 64K/2M/1G pages this
> apparent recycling will manifest into lots of really, really subtle
> bugs.
> 
> v2: Fix the testing of vma->flags for aliasing_ppgtt_bind_vma
> 
> Fixes: ff685975d97f ("drm/i915: Move allocate_va_range to GTT")
> Signed-off-by: Matthew Auld <matthew.auld at intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>

So, we are missing coverage of PIN_UPDATE and set-cache-level from the
kselftests. Ideas?

Matthew, do you have any clue how to reproduce those subtle errors?
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre