[igt-dev] [PATCH i-g-t v2 2/4] lib/intel_batchbuffer: add bb reset

[Chris Wilson]

Quoting Zbigniew Kempczyński (2020-06-04 11:03:51)
> +/**
> + * intel_bb_object_offset_to_buf:
> + * @ibb: pointer to intel_bb
> + * @buf: buffer we want to store last exec offset and context id
> + *
> + * Copy object offset used in the batch to intel_buf to allow caller prepare
> + * other batch likely without relocations.
> + */
> +bool intel_bb_object_offset_to_buf(struct intel_bb *ibb, struct intel_buf *buf)
> +{
> +       struct drm_i915_gem_exec_object2 object = { .handle = buf->handle };
> +       struct drm_i915_gem_exec_object2 **found;
> +
> +       igt_assert(ibb);
> +       igt_assert(buf);
> +
> +       found = tfind((void *) &object, &ibb->root, __compare_objects);
> +       if (!found) {
> +               buf->addr.offset = 0;
> +               buf->addr.ctx = 0;
> +
> +               return false;
> +       }
> +
> +       buf->addr.offset = (*found)->offset;
> +       buf->addr.ctx = ibb->ctx;

Ok, so it's tracking ctx so that we can return the right offset when the
buffer is used by multiple contexts. But ctx is never compared in the
lookup?

[There's also the problem of uint32_t ctx reuse, except there it can
probably happily inherit the old addr.]
-Chris