[Intel-gfx] [RFC] drm/i915/selftests: Fix overwriting ggtt

[Tvrtko Ursulin]

On 04/10/2022 09:20, Niranjana Vishwanathapura wrote:
> Looks like vma and gtt mock selftests overwrite the ggtt
> initialized by mock_gem_device() by calling intel_gt_assign_ggtt()
> and mock_init_ggtt() functions.
> The side effect seems to be mock_destroy_device() tries to
> release the ggtt already released by mock_fini_ggtt() instead of
> releasing the ggtt created by mock_gem_device() function.
> 
> I ran into this issue with vm_bind patch series.
> https://patchwork.freedesktop.org/series/105879/#rev5
> 
> I am fixing the vm_bind patch series by remvoing the vm->root_obj
> initialization for ggtt (it is required only for ppgtt upon user
> request).
> 
> But we need to address the underlying problem.
> But with this patch, I am seeing some of the vma and gtt mock
> selftests run into other crashes. So, this patch is not complete
> and I am missing the big picture here. Hence this RFC.

Adding some cc based on latest changes in the area being cdeea858d8df 
("drm/i915: Remove unused i915->ggtt"). No implications intended just 
trying to help with brainstorming the problem.

Regards,

Tvrtko

> Signed-off-by: Niranjana Vishwanathapura <niranjana.vishwanathapura at intel.com>
> ---
>   drivers/gpu/drm/i915/selftests/i915_gem_gtt.c | 16 ++--------------
>   drivers/gpu/drm/i915/selftests/i915_vma.c     | 16 ++--------------
>   2 files changed, 4 insertions(+), 28 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/selftests/i915_gem_gtt.c b/drivers/gpu/drm/i915/selftests/i915_gem_gtt.c
> index ea2cf1080979..9b0dae1d1a68 100644
> --- a/drivers/gpu/drm/i915/selftests/i915_gem_gtt.c
> +++ b/drivers/gpu/drm/i915/selftests/i915_gem_gtt.c
> @@ -1919,30 +1919,18 @@ int i915_gem_gtt_mock_selftests(void)
>   		SUBTEST(igt_gtt_insert),
>   	};
>   	struct drm_i915_private *i915;
> -	struct intel_gt *gt;
>   	int err;
>   
>   	i915 = mock_gem_device();
>   	if (!i915)
>   		return -ENOMEM;
>   
> -	/* allocate the ggtt */
> -	err = intel_gt_assign_ggtt(to_gt(i915));
> -	if (err)
> -		goto out_put;
> -
> -	gt = to_gt(i915);
> -
> -	mock_init_ggtt(gt);
> -
> -	err = i915_subtests(tests, gt->ggtt);
> +	err = i915_subtests(tests, to_gt(i915)->ggtt);
>   
>   	mock_device_flush(i915);
>   	i915_gem_drain_freed_objects(i915);
> -	mock_fini_ggtt(gt->ggtt);
> -
> -out_put:
>   	mock_destroy_device(i915);
> +
>   	return err;
>   }
>   
> diff --git a/drivers/gpu/drm/i915/selftests/i915_vma.c b/drivers/gpu/drm/i915/selftests/i915_vma.c
> index 71b52d5efef4..dbe78ed408e5 100644
> --- a/drivers/gpu/drm/i915/selftests/i915_vma.c
> +++ b/drivers/gpu/drm/i915/selftests/i915_vma.c
> @@ -923,30 +923,18 @@ int i915_vma_mock_selftests(void)
>   		SUBTEST(igt_vma_partial),
>   	};
>   	struct drm_i915_private *i915;
> -	struct intel_gt *gt;
>   	int err;
>   
>   	i915 = mock_gem_device();
>   	if (!i915)
>   		return -ENOMEM;
>   
> -	/* allocate the ggtt */
> -	err = intel_gt_assign_ggtt(to_gt(i915));
> -	if (err)
> -		goto out_put;
> -
> -	gt = to_gt(i915);
> -
> -	mock_init_ggtt(gt);
> -
> -	err = i915_subtests(tests, gt->ggtt);
> +	err = i915_subtests(tests, to_gt(i915)->ggtt);
>   
>   	mock_device_flush(i915);
>   	i915_gem_drain_freed_objects(i915);
> -	mock_fini_ggtt(gt->ggtt);
> -
> -out_put:
>   	mock_destroy_device(i915);
> +
>   	return err;
>   }
>