[Intel-xe] [PATCH] drm/xe/display: fix bo leak when unloading module

[Matthew Auld]

On Fri, 17 Feb 2023 at 10:37, Matthew Auld <matthew.auld at intel.com> wrote:
>
> One of the issues affecting module unload (DG2 + display) appears to be
> some kind of BO leak:
>
> WARNING: CPU: 1 PID: 1198 at drivers/gpu/drm/drm_mm.c:999 drm_mm_takedown+0x2e/0xc0
> WARNING: CPU: 1 PID: 1198 at drivers/gpu/drm/drm_buddy.c:174 drm_buddy_fini+0x5e/0x70 [drm_buddy]
>
> Turning on more debugging points at:
>
> [drm:drm_mm_takedown] *ERROR* node [00e10000 + 00e11000]: inserted at
>   drm_mm_insert_node_in_range+0x2c8/0x500
>   __xe_ggtt_insert_bo_at+0xb0/0x120 [xe]
>   xe_bo_create_locked_range+0x255/0x2d0 [xe]
>   xe_bo_create_pin_map_at+0x4d/0x170 [xe]
>   intel_alloc_initial_plane_obj.isra.0+0x175/0x340 [xe]
>   intel_crtc_initial_plane_config+0x7e/0x270 [xe]
>   intel_modeset_init_nogem+0x341/0x8b0 [xe]
>   xe_display_init_noaccel+0x1e/0x50 [xe]
>   xe_device_probe+0x1fa/0x2a0 [xe]
>
> So looks like we are leaking the object ref for the initial fb. Looking
> at the i915 code we also drop the driver reference to the underlying BO,
> which appears to just leave the drm framebuffer holding the last ref. Do
> the same for Xe.
>
> Signed-off-by: Matthew Auld <matthew.auld at intel.com>
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>

Gentle ping. Maarten, any chance you can take a look at this change?

> ---
>  drivers/gpu/drm/xe/display/xe_plane_initial.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/drivers/gpu/drm/xe/display/xe_plane_initial.c b/drivers/gpu/drm/xe/display/xe_plane_initial.c
> index bd5d588e8fbf..a2ef0823ed02 100644
> --- a/drivers/gpu/drm/xe/display/xe_plane_initial.c
> +++ b/drivers/gpu/drm/xe/display/xe_plane_initial.c
> @@ -230,6 +230,8 @@ intel_find_initial_plane_obj(struct intel_crtc *crtc,
>
>         atomic_or(plane->frontbuffer_bit, &to_intel_framebuffer(fb)->bits);
>
> +       plane_config->vma = vma;
> +
>         /*
>          * Flip to the newly created mapping ASAP, so we can re-use the
>          * first part of GGTT for WOPCM, prevent flickering, and prevent
> @@ -263,6 +265,9 @@ static void plane_config_fini(struct intel_initial_plane_config *plane_config)
>                 else
>                         kfree(fb);
>         }
> +
> +       if (plane_config->vma)
> +               drm_gem_object_put(&plane_config->vma->bo->ttm.base);
>  }
>
>  void intel_crtc_initial_plane_config(struct intel_crtc *crtc)
> --
> 2.39.1
>