[Intel-gfx] [PATCH v3 5/7] drm/i915: add a new perf configuration execbuf parameter

[Chris Wilson]

Quoting Lionel Landwerlin (2019-06-04 14:11:38)
>         list_add_tail(&rq->client_link, &rq->file_priv->mm.request_list);
>  }
>  
> +static int eb_oa_config(struct i915_execbuffer *eb)
> +{
> +       struct i915_vma *oa_vma;
> +       int err;
> +
> +       if (!eb->oa_config)
> +               return 0;
> +
> +       /*
> +        * If the config hasn't changed, skip reconfiguring the HW (this is
> +        * subject to a delay we want to avoid has much as possible).
> +        */
> +       if (eb->oa_config == eb->i915->perf.oa.exclusive_stream->oa_config)
> +               return 0;

But you don't order the execution so it may not be the right oa_config.
Just add the barrier. It is virtually no cost for the exclusive oa
userspace.

How does this interact with the global oa_config being changed via the
ioctl? What significance is there for this per-execbuf oa_config being
applied to other users?
-Chris