Re: [PATCH i-g-t] i915/gem_engine_topology: Introduce and use gem_context_clone_with_engines

[Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>]

Quoting Tvrtko Ursulin (2020-01-23 12:43:06)
> From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> 
> In test cases which create new contexts and submit work against them using
> the passed in engine index we are sometimes unsure whether this engine
> index was potentially created based on a default context with engine map
> configured (such as when under the __for_each_physical_engine iterator.
> 
> To simplify test code we add gem_context/queue_clone_with_engines which
> is to be used in such scenario instead of the current pattern of
> gem_context_create followed by gem_context_set_all_engines (which is also
> removed by the patch).
> 
> Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> Suggested-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> ---
>  lib/i915/gem_context.c         | 59 ++++++++++++++++++++++++++++++++++
>  lib/i915/gem_context.h         |  4 +++
>  lib/i915/gem_engine_topology.c | 11 -------
>  lib/i915/gem_engine_topology.h |  2 --
>  tests/i915/gem_ctx_clone.c     | 15 +--------
>  tests/i915/gem_ctx_switch.c    | 19 ++++-------
>  tests/i915/gem_exec_parallel.c |  3 +-
>  tests/i915/gem_spin_batch.c    | 11 +++----
>  tests/perf_pmu.c               |  3 +-
>  9 files changed, 76 insertions(+), 51 deletions(-)
> 
> diff --git a/lib/i915/gem_context.c b/lib/i915/gem_context.c
> index 1fae5191f83f..f92d5ff3dfc5 100644
> --- a/lib/i915/gem_context.c
> +++ b/lib/i915/gem_context.c
> @@ -372,6 +372,50 @@ uint32_t gem_context_clone(int i915,
>         return ctx;
>  }
>  
> +bool gem_has_context_clone(int i915)
> +{
> +       struct drm_i915_gem_context_create_ext_clone ext = {
> +               { .name = I915_CONTEXT_CREATE_EXT_CLONE },
> +               .clone_id = -1,
> +       };
> +       struct drm_i915_gem_context_create_ext create = {
> +               .flags = I915_CONTEXT_CREATE_FLAGS_USE_EXTENSIONS,
> +               .extensions = to_user_pointer(&ext),
> +       };
> +       int err;
> +
> +       err = 0;
> +       if (igt_ioctl(i915, DRM_IOCTL_I915_GEM_CONTEXT_CREATE_EXT, &create)) {
> +               err = -errno;
> +               igt_assume(err);
> +       }
> +       errno = 0;
> +
> +       return err == -ENOENT;
> +}
> +
> +/**
> + * gem_context_clone_with_engines:
> + * @i915: open i915 drm file descriptor
> + * @src: i915 context id
> + *
> + * Special purpose wrapper to create a new context by cloning engines from @src.
> + *
> + * In can be called regardless of whether the kernel supports context cloning.
> + *
> + * Intended purpose is to use for creating contexts against which work will be
> + * submitted and the engine index came from external source, derived from a
> + * default context potentially configured with an engine map.
> + */
> +uint32_t gem_context_clone_with_engines(int i915, uint32_t src)
> +{
> +       if (!gem_has_context_clone(i915))
> +               return gem_context_create(i915);

Yes, that should cover us for older kernels and keep the for_each loops
happy.

> +       else
> +               return gem_context_clone(i915, src, 0,
> +                                        I915_CONTEXT_CLONE_ENGINES);

0 and CLONE are the wrong way around.

I would have done

int __gem_context_clone_with_engines(int i915, uint32_t src, uint32_t *out)
{
	int err;

	err = __gem_context_clone(i915, src, CLONE_ENGINES, 0, out);
	if (err && !gem_has_context_clone(i915))
		err = __gem_context_create(i915, out);

	return err;
}

uint32_t gem_context_clone_with_engines(int i915, uint32_t src)
{
	uint32_t ctx;

	igt_assert_eq(__gem_context_clone_with_engine(i915, src, &ctx), 0);

	return ctx;
}

> diff --git a/lib/i915/gem_engine_topology.c b/lib/i915/gem_engine_topology.c
> index 989a6e26d6ef..43a99e0ff680 100644
> --- a/lib/i915/gem_engine_topology.c
> +++ b/lib/i915/gem_engine_topology.c
> @@ -274,17 +274,6 @@ int gem_context_lookup_engine(int fd, uint64_t engine, uint32_t ctx_id,
>         return 0;
>  }
>  
> -void gem_context_set_all_engines(int fd, uint32_t ctx)
> -{
> -       DEFINE_CONTEXT_ENGINES_PARAM(engines, param, ctx, GEM_MAX_ENGINES);
> -       struct intel_engine_data engine_data = { };
> -
> -       if (!gem_topology_get_param(fd, &param) && !param.size) {
> -               query_engine_list(fd, &engine_data);
> -               ctx_map_engines(fd, &engine_data, &param);
> -       }
> -}

Me likes.
-Chris
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