Re: [igt-dev] [PATCH v3 2/3] lib: implement new engine discovery interface

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 26/11/2018 20:43, Andi Shyti wrote:
> Kernel commits:
> 
> [1] ae8f4544dd8f ("drm/i915: Engine discovery query")
> [2] 31e7d35667a0 ("drm/i915: Allow a context to define its set of engines")
> 
> from [*] repository, implement a new uapi for engine discovery
> that consist in first querying the driver about the engines in
> the gpu [1] and then binding a context to the set of engines that
> it can access [2].
> 
> In igt the classic way for discovering engines is done through
> the for_each_physical_engine() macro, that would be replaced by
> the new for_each_engine_ctx().
> 
> [*] git://people.freedesktop.org/~tursulin/drm-intel
> 
> Signed-off-by: Andi Shyti <andi.shyti@intel.com>
> ---
>   lib/igt_gt.c | 74 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>   lib/igt_gt.h |  5 ++++
>   2 files changed, 79 insertions(+)
> 
> diff --git a/lib/igt_gt.c b/lib/igt_gt.c
> index a2061924..e5543b27 100644
> --- a/lib/igt_gt.c
> +++ b/lib/igt_gt.c
> @@ -650,3 +650,77 @@ bool gem_ring_has_physical_engine(int fd, unsigned ring)
>   
>   	return gem_has_ring(fd, ring);
>   }
> +
> +static struct drm_i915_query_engine_info *query_engines(int fd)
> +{
> +	struct drm_i915_query query = { };
> +	struct drm_i915_query_item item = { };
> +	struct drm_i915_query_engine_info *query_engines;
> +
> +	item.query_id = DRM_I915_QUERY_ENGINE_INFO;
> +	query.items_ptr = to_user_pointer(&item);
> +	query.num_items = 1;
> +
> +	/*
> +	 * The first ioctl is sent with item.length = 0
> +	 * which asks to the driver to store in length the
> +	 * memory needed for the engines. In the driver, length
> +	 * is equal to
> +	 *
> +	 *   len = sizeof(struct drm_i915_query_engine_info) +
> +	 *                   INTEL_INFO(i915)->num_rings *
> +	 *                   sizeof(struct drm_i915_engine_info);
> +	 */
> +	igt_require(!ioctl(fd, DRM_IOCTL_I915_QUERY, &query));
> +
> +	igt_assert((query_engines = calloc(item.length, 1)));
> +	item.data_ptr = to_user_pointer(query_engines);
> +
> +	/* The second ioctl stores the engines in query_engines */
> +	igt_require(!ioctl(fd, DRM_IOCTL_I915_QUERY, &query));
> +
> +	return query_engines;
> +}
> +
> +static void set_param(int fd, uint32_t ctx_id,
> +		      struct drm_i915_query_engine_info *query_engine)
> +{
> +	int i;
> +	struct drm_i915_gem_context_param ctx_param;
> +	struct i915_context_param_engines *ctx_engine;
> +	size_t size = sizeof(struct i915_context_param_engines) +
> +		      query_engine->num_engines *
> +		      sizeof(*ctx_engine->class_instance);
> +
> +	igt_assert((ctx_engine = malloc(size)));
> +
> +	ctx_engine->extensions = 0;
> +	for (i = 0; i < query_engine->num_engines; i++) {
> +		ctx_engine->class_instance[i].class = query_engine->engines[i].class;
> +		ctx_engine->class_instance[i].instance = query_engine->engines[i].instance;
> +	}
> +
> +	ctx_param.ctx_id = ctx_id;
> +	ctx_param.size = size;
> +	ctx_param.param = I915_CONTEXT_PARAM_ENGINES;
> +	ctx_param.value = to_user_pointer(ctx_engine);
> +
> +	/* check whether we free the engines */
> +	igt_require(!ioctl(fd, DRM_IOCTL_I915_GEM_CONTEXT_SETPARAM, &ctx_param));
> +
> +	free(ctx_engine);

Leaks on skip, not that it matters a lot, but the comments makes me 
think you wanted to handle it.

> +}
> +
> +int __gem_setup_ctx_engines(int fd, uint32_t ctx_id)
> +{
> +	struct drm_i915_query_engine_info *query_engine;
> +	int n;
> +
> +	query_engine = query_engines(fd);
> +	set_param(fd, ctx_id, query_engine);
> +
> +	n = query_engine->num_engines;
> +	free(query_engine);
> +
> +	return n;
> +}
> diff --git a/lib/igt_gt.h b/lib/igt_gt.h
> index 54e95da9..512f958d 100644
> --- a/lib/igt_gt.h
> +++ b/lib/igt_gt.h
> @@ -86,8 +86,13 @@ extern const struct intel_execution_engine {
>   	     e__++) \
>   		for_if (gem_ring_has_physical_engine(fd__, flags__ = e__->exec_id | e__->flags))
>   
> +#define for_each_engine_ctx(fd, ctx, e) \
> +		for (int __m = __gem_setup_ctx_engines(fd, ctx), __e = e = 1; \
> +				__e <= __m; e = ++__e)
> +

Is __e needed? Could just use passed in e?

>   bool gem_ring_is_physical_engine(int fd, unsigned int ring);
>   bool gem_ring_has_physical_engine(int fd, unsigned int ring);
> +int __gem_setup_ctx_engines(int fd, uint32_t ctx_id);
>   
>   bool gem_can_store_dword(int fd, unsigned int engine);
>   
> 

Looks okay. But we need to decide whether we want the iterator to be a 
struct sooner rather than later now.

I think if you go and convert one of the tests which uses 
for_each_physical_engine to enumerate subtests and so, it will become 
clearer what approach work better. (struct iterator, or helpers to get 
data from engine index.)

Regards,

Tvrtko

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