[Intel-gfx] [PATCH] drm/i915/hangcheck: Prevent long walks across full-ppgtt

[Chris Wilson]

On Wed, Mar 02, 2016 at 04:48:29PM +0200, Mika Kuoppala wrote:
> With full-ppgtt, it takes the GPU an eon to traverse the entire 256PiB
> address space, causing a loop to be detected. Under the current scheme,
> if ACTHD walks off the end of a batch buffer and into an empty
> address space, we "never" detect the hang. If we always increment the
> score as the ACTHD is progressing then we will eventually timeout (after
> ~46.5s (31 * 1.5s) without advancing onto a new batch). To counter act
> this, increase the amount we reduce the score for good batches, so that
> only a series of almost-bad batches trigger a full reset. DoS detection
> suffers slightly but series of long running shader tests will benefit.
> 
> Based on a patch from Chris Wilson.
> 
> Testcase: igt/drv_hangman/hangcheck-unterminated
> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Signed-off-by: Mika Kuoppala <mika.kuoppala at intel.com>
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre