[Intel-gfx] [PATCH 3/3] drm/i915: Assert the csb tail is within bounds

[Chris Wilson]

Quoting Mika Kuoppala (2018-11-27 17:38:45)
> Make sure that the tail we get from hardware fits
> within the bounds dictated by our count of csb entries.
> 
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> Signed-off-by: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_lrc.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index 107244ab09ef..1a34e91c1305 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -888,6 +888,7 @@ static void process_csb(struct intel_engine_cs *engine)
>          */
>         head = execlists->csb_head;
>         tail = READ_ONCE(*execlists->csb_write);
> +       GEM_DEBUG_BUG_ON(tail >= execlists->csb_entries);
>         GEM_TRACE("%s cs-irq head=%d, tail=%d\n", engine->name, head, tail);

Apply the assert after the debug trace.
-Chris