Re: [PATCH i-g-t] i915/gem_ctx_persistence: Check that we cannot hide hangs on old engines

[Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxxxxxxxx>]

On 05/02/2020 13:48, Chris Wilson wrote:
> As the kernel loses track of the context's old engines, if we request
> that the context is non-persistent then any request on the untracked
> engines must be cancelled.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> ---
>   tests/i915/gem_ctx_persistence.c | 60 +++++++++++++++++++++++++++++++-
>   1 file changed, 59 insertions(+), 1 deletion(-)
>
> diff --git a/tests/i915/gem_ctx_persistence.c b/tests/i915/gem_ctx_persistence.c
> index c54797e9b..04a6c179e 100644
> --- a/tests/i915/gem_ctx_persistence.c
> +++ b/tests/i915/gem_ctx_persistence.c
> @@ -761,6 +761,49 @@ static void smoketest(int i915)
>   	gem_quiescent_gpu(i915);
>   }
>   
> +static void replace_engines_hostile(int i915,
> +				    const struct intel_execution_engine2 *e)
> +{
> +	I915_DEFINE_CONTEXT_PARAM_ENGINES(engines, 1) = {
> +		.engines = {{ e->class, e->instance }}
> +	};
> +	struct drm_i915_gem_context_param param = {
> +		.ctx_id = gem_context_create(i915),
> +		.param = I915_CONTEXT_PARAM_ENGINES,
> +		.value = to_user_pointer(&engines),
> +		.size = sizeof(engines),
> +	};
> +	igt_spin_t *spin[2];
> +	int64_t timeout;
> +
> +	/*
> +	 * Suppose the user tries to hide a hanging batch by replacing
> +	 * the set of engines on the context so that it's not visible
> +	 * at the time of closure? Then we must act when they replace
> +	 * the engines!
> +	 */
> +
> +	gem_context_set_persistence(i915, param.ctx_id, false);
> +
> +	gem_context_set_param(i915, &param);
> +	spin[0] = igt_spin_new(i915, param.ctx_id);
> +
> +	gem_context_set_param(i915, &param);
> +	spin[1] = igt_spin_new(i915, param.ctx_id);
> +
> +	gem_context_destroy(i915, param.ctx_id);

At this point context_close() -> kill_context() but spin[0] 
intel_context no longer in ctx->engines so hangs. spin[1] is terminated.

> +
> +	timeout = reset_timeout_ms * NSEC_PER_MSEC;
> +	igt_assert_eq(gem_wait(i915, spin[1]->handle, &timeout), 0);
> +
> +	timeout = reset_timeout_ms * NSEC_PER_MSEC;
> +	igt_assert_eq(gem_wait(i915, spin[0]->handle, &timeout), 0);
> +
> +	igt_spin_free(i915, spin[1]);
> +	igt_spin_free(i915, spin[0]);
> +	gem_quiescent_gpu(i915);
> +}
> +
>   int i915;
>   
>   static void exit_handler(int sig)
> @@ -793,10 +836,10 @@ igt_main
>   		igt_assert(igt_sysfs_set_parameter
>   			   (i915, "reset", "%d", -1 /* any [default] reset */));
>   
> -		igt_require(has_persistence(i915));
>   		enable_hangcheck(i915);
>   		igt_install_exit_handler(exit_handler);
>   
> +		igt_require(has_persistence(i915));
>   		igt_allow_hang(i915, 0, 0);
>   	}
>   
> @@ -861,6 +904,21 @@ igt_main
>   			smoketest(i915);
>   	}
>   
> +	/* Check interactions with set-engines */
> +	igt_subtest_group {
> +		const struct intel_execution_engine2 *e;
> +
> +		igt_fixture
> +			gem_require_contexts(i915);
> +
> +		igt_subtest_with_dynamic("replace-hostile") {
> +			__for_each_physical_engine(i915, e) {
> +				igt_dynamic_f("%s", e->name)
> +					replace_engines_hostile(i915, e);
> +			}
> +		}
> +	}
> +
>   	igt_fixture {
>   		close(i915);
>   	}

Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>

Regards,

Tvrtko
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