[Intel-gfx] [PATCH 2/2] drm/i915/guc: Don't make assumptions while getting the lrca offset

[Chris Wilson]

Quoting Michel Thierry (2017-07-12 20:30:32)
> Using the HWSP ggtt_offset to get the lrca offset is only correct if the
> HWSP happens to be before it (when we reuse the PPHWSP of the kernel
> context as the engine HWSP). Instead of making this assumption, get the
> lrca offset from the kernel_context engine state.
> 
> And while looking at this part of the GuC interaction, it was also
> noticed that the firmware expects the size of only the engine context
> (context minus the execlist part, i.e. don't include the first 80
> dwords), so pass the right size.
> 
> v2: Use the new macros to prevent abusive overuse of the old ones (Chris).
> 
> Reported-by: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> Signed-off-by: Michel Thierry <michel.thierry at intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> Cc: Michal Wajdeczko <michal.wajdeczko at intel.com>
> Cc: Oscar Mateo <oscar.mateo at intel.com>
> ---
>  drivers/gpu/drm/i915/i915_guc_submission.c | 21 ++++++++++++++++++---
>  1 file changed, 18 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_guc_submission.c b/drivers/gpu/drm/i915/i915_guc_submission.c
> index b7ca13860677..8b96935cf96a 100644
> --- a/drivers/gpu/drm/i915/i915_guc_submission.c
> +++ b/drivers/gpu/drm/i915/i915_guc_submission.c
> @@ -1018,6 +1018,12 @@ static void guc_policies_init(struct guc_policies *policies)
>         policies->is_valid = 1;
>  }
>  
> +/*
> + * The first 80 dwords of the register state context, containing the
> + * execlists and ppgtt registers.
> + */
> +#define LR_HW_CONTEXT_SIZE     (80 * sizeof(u32))
> +
>  static int guc_ads_create(struct intel_guc *guc)
>  {
>         struct drm_i915_private *dev_priv = guc_to_i915(guc);
> @@ -1032,6 +1038,8 @@ static int guc_ads_create(struct intel_guc *guc)
>         } __packed *blob;
>         struct intel_engine_cs *engine;
>         enum intel_engine_id id;
> +       const u32 skipped_offset = LRC_HEADER_PAGES * PAGE_SIZE;
> +       const u32 skipped_size = LRC_PPHWSP_SZ * PAGE_SIZE + LR_HW_CONTEXT_SIZE;

I think I preferred the constants rather than the variables, but that's
a matter of taste. Since you confirmed the guc works the way you
describe and now have a big warning in place,

Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>

Though I would get Daniele to confirm the interpretation.
-Chris