[Intel-gfx] [PATCH] drm/i915: Enforce that CS packets are qword aligned

[Chris Wilson]

Quoting Chris Wilson (2017-07-21 17:11:01)
> We require the caller to ensure that the packets they wish to emit into
> the CS ring are qword aligned (i.e. have an even number of dwords).
> Double check this.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_ringbuffer.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index aa59290cb8bf..0b06f66507a0 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -1397,6 +1397,9 @@ u32 *intel_ring_begin(struct drm_i915_gem_request *req,
>         unsigned int total_bytes;
>         u32 *cs;
>  
> +       /* Packets must be qword aligned. */
> +       GEM_BUG_ON(num_dwords & 1);

GEM_BUG_ON(!IS_ALIGNED(num_dwords, 2)) ?
GEM_BUG_ON(!IS_ALIGNED(num_words, DWORDS_PER_QWORD)) ?
-Chris