[Mesa-dev] [PATCH v3 2/3] i965: add noise padding to buffer object and function to check if noise is correct

[Chris Wilson]

Quoting kevin.rogovin at intel.com (2018-01-09 12:21:29)
> From: Kevin Rogovin <kevin.rogovin at intel.com>
> 
> Signed-off-by: Kevin Rogovin <kevin.rogovin at intel.com>
> ---
> +bool
> +brw_bo_padding_is_good(struct brw_bo *bo)
> +{
> +   if (bo->padding_size > 0) {
> +      struct drm_i915_gem_mmap mmap_arg = {
> +         .handle = bo->gem_handle,
> +         .offset = bo->size,
> +         .size = bo->padding_size,
> +         .flags = 0,
> +      };
> +      uint8_t *mapped;
> +      int ret;
> +      uint8_t expected_value;
> +
> +      /* We cannot use brw_bo_map() because it maps precisely the range
> +       * [0, bo->size) and we wish to map the range of the padding which
> +       * is [bo->size, bo->size + bo->pading_size)
> +       */
> +      ret = drmIoctl(bo->bufmgr->fd, DRM_IOCTL_I915_GEM_MMAP, &mmap_arg);
> +      if (ret != 0) {
> +         DBG("Unable to map mapping buffer %d (%s) buffer for pad checking.\n",
> +             bo->gem_handle, bo->name);
> +         return false;
> +      }
> +
> +      mapped = (uint8_t*) (uintptr_t) mmap_arg.addr_ptr;
> +      /* bah-humbug, we need to see the latest contents and
> +       * if the bo is not cache coherent we likely need to
> +       * invalidate the cache lines to get it.
> +       */
> +      if (!bo->cache_coherent && !bo->bufmgr->has_llc) {
> +         gen_invalidate_range(mapped, bo->padding_size);
> +      }
> +
> +      expected_value = bo->gem_handle & 0xFF;
> +      for (uint32_t i = 0; i < bo->padding_size; ++i) {
> +         if (expected_value != mapped[i]) {
> +            drm_munmap(mapped, bo->padding_size);
> +            return false;
> +         }
> +         expected_value = next_noise_value(expected_value);
> +      }
> +      drm_munmap(mapped, bo->padding_size);
> +   }
> +   return true;
> +}

Looks good from the uabi pov and interaction with brw_bo.
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>

I've a few stylistic nitpicks, but that's better handled by
Kenneth and/or Ian, as I very rarely get the mesa coding style right
myself :)
-Chris