[PATCH v8 05/12] drm/i915: don't whitelist oacontrol in cmd parser

[sourab gupta]

On Thu, 2016-10-27 at 19:14 -0700, Robert Bragg wrote:
> Being able to program OACONTROL from a non-privileged batch buffer is
> not sufficient to be able to configure the OA unit. This was originally
> allowed to help enable Mesa to expose OA counters via the
> INTEL_performance_query extension, but the current implementation based
> on programming OACONTROL via a batch buffer isn't able to report useable
> data without a more complete OA unit configuration. Mesa handles the
> possibility that writes to OACONTROL may not be allowed and so only
> advertises the extension after explicitly testing that a write to
> OACONTROL succeeds. Based on this; removing OACONTROL from the whitelist
> should be ok for userspace.
> 
> Removing this simplifies adding a new kernel api for configuring the OA
> unit without needing to consider the possibility that userspace might
> trample on OACONTROL state which we'd like to start managing within
> the kernel instead. In particular running any Mesa based GL application
> currently results in clearing OACONTROL when initializing which would
> disable the capturing of metrics.
> 
> Signed-off-by: Robert Bragg <robert at sixbynine.org>
> Reviewed-by: Matthew Auld <matthew.auld at intel.com>
Seems reasonable.
Reviewed-by: Sourab Gupta <sourab.gupta at intel.com>